Title:
STABLE, THIN-FILM ORGANIC PASSIVATES
Kind Code:
A1


Abstract:
An aqueous liquid passivate composition for treating metal surfaces having dispersed therein solid particles which result in a transparent or translucent, preferably colorless, corrosion resistant coating, upon drying of the aqueous liquid passivate composition, the coating providing better resistance to heating by solar energy than the untreated metal surface at lower coating thicknesses than paint.



Inventors:
Smith, Steven R. (Troy, MI, US)
Cape, Thomas W. (West Bloomfield, MI, US)
Sohi, Jasdeep (Shelby Township, MI, US)
Donaldson, Gregory T. (Sterling Heights, MI, US)
Mcgee, John D. (Troy, MI, US)
Smith II, Thomas S. (Novi, MI, US)
Bammel, Brian D. (Rochester Hills, MI, US)
Application Number:
11/566662
Publication Date:
06/07/2007
Filing Date:
12/04/2006
Primary Class:
Other Classes:
148/251
International Classes:
C23C22/26
View Patent Images:



Primary Examiner:
COHEN, STEFANIE J
Attorney, Agent or Firm:
HENKEL CORPORATION (One Henkel Way, ROCKY HILL, CT, 06067, US)
Claims:
1. A composition useful for passivating a metal surface, said composition comprising water and: (A) dispersed solid particles of metal and/or metalloid oxide, desirably the metal and/or metalloid oxide is a powder the particles preferably having a mean particle size of less or equal to 100 nm, and (B) dissolved, dispersed, or both dissolved and dispersed hexavalent chromium that is not part of immediately previously recited component (A); (C) dissolved, dispersed, or both dissolved and dispersed organic film-forming resin; and, optionally, one or more of the following components: (D) dissolved, dispersed, or both dissolved and dispersed pH adjusting agent that is not part of any one of immediately previously recited components (A) through (C); (E) dissolved, dispersed, or both dissolved and dispersed trivalent chromium that is not part of any one of immediately previously recited components (A) through (D); (F) dissolved, dispersed, or both dissolved and dispersed wax that is not part of immediately previously recited component (A) through (E); (G) at least one dissolved, dispersed, or both dissolved and dispersed surfactant and/or antiblocking agent that is not part of any of immediately previously recited components (A) through (F); (H) dissolved organic solvent that is not part of any of immediately previously recited components (A) through (G); (I) dissolved, dispersed, or both dissolved and dispersed material selected from the group consisting of (i) reducing agents that are capable, at a specified temperature, of reducing hexavalent chromium in the composition to trivalent chromium and (ii) oxidation products from a reducing agent that has reduced some initially hexavalent chromium in the composition to trivalent chromium, said dissolved, dispersed, or both dissolved and dispersed material not being part of any of immediately previously recited components (A) through (H); and (J) dissolved, dispersed, or both dissolved and dispersed colorant that is not part of any of immediately previously recited components (A) through (I); wherein said composition comprises less than 0.04 wt % chromium and dries to a transparent or translucent coating having an emittance of at least 0.60 and a reflectance of at least 0.60.

2. The composition of claim 1, wherein the total concentration of the complex fluoride is at least 0.5 g/L and is not more than 100 g/L.

3. The composition of claim 1, wherein the at least one complex fluoride is a titanium and/or zirconium complex fluoride.

4. The composition of claim 1, wherein said composition is essentially free of chromium, the resin comprises a non-ionic or non-ionically stabilized acrylic and/or acrylic copolymer resin in dispersed form, said composition comprising at least one pH adjusting component.

5. The composition of claim 1, wherein the pH of the composition is within a range of from about 1 to about 5 and the composition is storage stable at 100 deg. F. for at least 3 months.

6. The composition of claim 1, comprising at least one component that comprises vanadium.

7. The composition of claim 1, comprising at least one wax, selected from the group of waxes stable in strong acidic solutions having an average particle size less than about 1 micron and a melting point of from about 50 to about 175 degrees C.

8. The composition of claim 1, containing: (A) 25-75 weight % of at least one inorganic oxide in dispersed form, the particles preferably having a mean particle size of less than 100 nm; (B) 0.05-5 weight % of at least one complex fluoride of an element selected from the group consisting of Ti, Zr, Hf, Si, Sn, Al, Ge and B; preferably Ti and/or Zr; (C) 10-50 weight % of a non-ionic or non-ionically stabilized resin in dispersed form selected from the group consisting of acrylic, polyurethane, vinyl, and polyester resins, and mixtures thereof; (D) optionally, dissolved phosphate anions; (E) 0.1 to 7 weight % of at least one component comprising vanadium; (F) 0.05-20 weight % of at least one wax in dispersed form; (G) and optionally, at least one further additive selected from the group consisting of a sequestrant, a wetting agent, a defoamer, and a pH adjusting component; said composition comprising less than 0.04 wt % chromium.

9. A process of treating a ferriferous, aluminiferous or zinciferous metal substrate comprising: optionally, cleaning a surface of said metal substrate to be passivated; contacting the metal substrate surface to be passivated with a passivating composition for a time sufficient to form a coating on said metal surface, wherein the passivating composition comprises water and: (A) at least one inorganic oxide in dispersed form, the particles preferably having a mean particle size of less than 100 nm; (B) at least one complex fluoride of an element selected from the group consisting of Ti, Zr, Hf, Si, Sn, Al, Ge and B; preferably Ti and/or Zr; (C) a non-ionic or non-ionically stabilized resin in dispersed form selected from the group consisting of acrylic, polyurethane, vinyl, and polyester resins, and mixtures thereof; (D) optionally, dissolved phosphate anions; (E) optionally, at least one component comprising vanadium; (F) optionally, at least one wax in dispersed form; (G) and optionally, at least one further additive selected from the group consisting of a sequestrant, a wetting agent, a defoamer, and a pH adjusting component; said composition comprising less than 0.04 wt % chromium; and drying to form a transparent or translucent passivate coating having an emittance of 0.60 and a reflectance of 0.60, on the metal surface.

10. The process of claim 14 further comprising the step of coating the metal substrate with a dissimilar metal, thereby creating a metal substrate surface to be passivated, prior to contacting with the passivating composition.

11. A uniform and stable liquid composition of matter comprising water and the following components: (A) dispersed solid particles of metal and/or metalloid oxide having a mean particle size of less or equal to 100 nm, and (B) dissolved, dispersed, or both dissolved and dispersed hexavalent chromium that is not part of immediately previously recited component (A); (C) dissolved, dispersed, or both dissolved and dispersed organic film-forming resin; and, optionally, one or more of the following components: (D) dissolved, dispersed, or both dissolved and dispersed pH adjusting agent that is not part of any one of immediately previously recited components (A) through (C); (E) dissolved, dispersed, or both dissolved and dispersed trivalent chromium that is not part of any one of immediately previously recited components (A) through (D); (F) dissolved, dispersed, or both dissolved and dispersed wax that is not part of immediately previously recited component (A) through (E); (G) at least one dissolved, dispersed, or both dissolved and dispersed surfactant and/or antiblocking agent that is not part of any of immediately previously recited components (A) through (F); (H) dissolved organic solvent that is not part of any of immediately previously recited components (A) through (G); (I) dissolved, dispersed, or both dissolved and dispersed material selected from the group consisting of (i) reducing agents that are capable, at a specified temperature, of reducing hexavalent chromium in the composition to trivalent chromium and (ii) oxidation products from a reducing agent that has reduced some initially hexavalent chromium in the composition to trivalent chromium, said dissolved, dispersed, or both dissolved and dispersed material not being part of any of immediately previously recited components (A) through (H); and (J) dissolved, dispersed, or both dissolved and dispersed colorant that is not part of any of immediately previously recited components (A) through (I); wherein said composition dries to a transparent or translucent coating having an emittance of at least 0.60 and a reflectance of at least 0.60.

12. The composition of claim 11, wherein the dispersed solid particles of metal and/or metalloid oxide are selected from oxides of Ti, Zn, Zr, Sb, Al, Hf, and V.

13. The composition of claim 11, wherein the dispersed solid particles of metal and/or metalloid oxide are present in an amount of about 10.0 to about 80.0 weight %.

14. The composition of claim 11, wherein the dispersed solid particles of metal and/or metalloid oxide are selected such that the as-dried coating a clear, colorless coating after not more than 60 days.

15. The composition of claim 11, wherein the dispersed solid particles of metal and/or metalloid oxide are selected such that the coating has emittance of at least 0.60 at wavelengths of about 250 to about 2500 nm.

16. The composition of claim 11, wherein the dispersed solid particles of metal and/or metalloid oxide have a mean particle size range from about 1 to about 50 nanometers.

17. The composition of claim 11, wherein the dispersed solid particles of metal and/or metalloid oxide have a mean particle size range from about 5 to about 35 nanometers.

18. The composition of claim 11, wherein the dispersed solid particles of metal oxide are selected from oxides of Ti, Zn, Zr, Sb, Al, Hf, and V.

19. A process of treating a ferriferous, aluminiferous or zinciferous metal substrate comprising: optionally, cleaning a surface of said metal substrate to be passivated; contacting the metal substrate surface to be passivated with a passivating composition for a time sufficient to form a coating on said metal surface, wherein the passivating composition comprises water and: (A) dispersed solid particles of metal and/or metalloid oxide having a mean particle size of less or equal to 100 nm, and (B) dissolved, dispersed, or both dissolved and dispersed hexavalent chromium that is not part of immediately previously recited component (A); (C) dissolved, dispersed, or both dissolved and dispersed organic film-forming resin; and, optionally, one or more of the following components: (D) dissolved, dispersed, or both dissolved and dispersed pH adjusting agent that is not part of any one of immediately previously recited components (A) through (C); (E) dissolved, dispersed, or both dissolved and dispersed trivalent chromium that is not part of any one of immediately previously recited components (A) through (D); (F) dissolved, dispersed, or both dissolved and dispersed wax that is not part of immediately previously recited component (A) through (E); (G) at least one dissolved, dispersed, or both dissolved and dispersed surfactant and/or antiblocking agent that is not part of any of immediately previously recited components (A) through (F); (H) dissolved organic solvent that is not part of any of immediately previously recited components (A) through (G); (I) dissolved, dispersed, or both dissolved and dispersed material selected from the group consisting of (i) reducing agents that are capable, at a specified temperature, of reducing hexavalent chromium in the composition to trivalent chromium and (ii) oxidation products from a reducing agent that has reduced some initially hexavalent chromium in the composition to trivalent chromium, said dissolved, dispersed, or both dissolved and dispersed material not being part of any of immediately previously recited components (A) through (H); and (J) dissolved, dispersed, or both dissolved and dispersed colorant that is not part of any of immediately previously recited components (A) through (I); drying to form a passivate coating having an emittance of 0.60 and a reflectance of 0.60 and a thickness of 12 microns or less, on the metal surface.

20. The process of claim 19 further comprising the step of coating the metal substrate with a dissimilar metal, thereby creating a metal substrate surface to be passivated, prior to contacting with the passivating composition.

Description:

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation in part of U.S. application Ser. No. 11/330869, filed 12 Jan. 2006, which claims priority to U.S. Provisional Application Ser. No. 60/644,191, filed 14 Jan. 2005, each of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to compositions and processes for passivating, i.e., forming a corrosion resistant surface layer, on metal surfaces preferably predominantly of aluminum and/or zinc, which also improves the metal surface's resistance to heating by electromagnetic radiation (hereinafter EMR), in particular solar radiation or energy. A wide variety of such surfaces are in normal use, including many kinds of galvanized and/or aluminized steel, and the invention is applicable to aluminiferous and/or zinciferous surfaces which differ from the underlying metal, as well as to solid alloys of aluminum and/or zinc which include zinc, such as hot-dip and electro-galvanized, zinc alloys, aluminum, aluminum alloys and mixtures thereof, as well as steel coated with these metals (hereinafter referred to as zinc- and/or aluminum-containing metal surfaces).

BACKGROUND OF THE INVENTION

Zinc (zinciferous) and zinc alloy (such as aluminiferous) coatings are frequently used to protect steel from corrosion. Two common types of metal-coated steel typically used are galvanized steel (zinc), such as hot-dip, electrogalvanized and Galvanneal®, as well as zinc aluminum alloys such as Galfan® and Galvalume® (55% Al, 43.5% Zn, 1.5% Si). The thus coated steels have long service lifetimes as a result of galvanic and/or sacrificial corrosion protection of the underlying substrate afforded by the coatings. While the underlying steel substrate is protected, the aluminum and zinc coating are sometimes susceptible to corrosion that can result in surface staining and white corrosion.

A variety of treatments can be used to prevent corrosion of ferriferous, zinciferous and aluminiferous surfaces. These include phosphate conversion coating followed by application of an oil, which provides some short term protection, but requires removal of the oil prior to painting. Also, well known in the industry are phosphate conversion coatings, with or without a subsequent painting step. Inorganic passivates, typically using chromium, provide excellent passivation but have the drawbacks of poor paint adhesion and adverse environmental impact.

Thin-film organic passivates are used industrially to provide corrosion protection to zinc- and/or aluminum-containing metal surfaces, including zinc coated or zinc alloy coated steel. In addition these coatings provide lubricity to facilitate roll forming of steel coils. The thin-film organic passivates are distinguished from typical phosphate conversion coatings by, for example, the presence of organic film forming resin and the amount of protection provided by the coating. Known phosphate conversion coatings generally require an overcoating of paint to achieve adequate corrosion resistance.

Traditionally, most zinciferous and/or aluminiferous surfaces have been passivated by chemical treatment with aqueous liquid compositions containing at least some hexavalent chromium. Thin-film organic passivates generally comprise an organic film forming resin, typically an aqueous dispersion or latex; a surface passivating material, most often a hexavalent chromium containing substance; water and optional additives.

Various attempts have been made to make alternatives to the chromium-containing products by substituting other metals for the chromium in the latex-based passivate treatment products. The alternative products included various metal ions and tend to have a very low pH, that is in the range of pH about 1-2. Many of these attempts failed where the latex became unstable and the formulation coagulated, due at least in part to the low pH and the presence of other ingredients, such as metal ions. Often, even if the formulation did not immediately coagulate, the chromium-free products had little or no shelf life, either separating or coagulating over a matter of days or even hours.

Another drawback of prior art organic passivating compositions is their undesirable effects on the physical attributes of coils of metal. In the coil industry, lengths of sheet metal are typically galvanically coated and passivated in a continuous process. The metal is then coiled for storage and transport, ordinarily while still at elevated temperature. These coils are later unwound as the sheet metal is introduced into a metal forming operation, such as stamping. The metal is cut into selected lengths and formed into component parts of, by way of non-limiting example, appliances, automobiles, furniture. In this industry, the nature of the passivate coating can have undesirable effects of binding or slippage between metal surfaces in the coil. Each undesirable effect causes problems in manufacture; binding refers to the coils sticking together and interferes with uncoiling, and slipping/sliding of the metal surfaces relative to each other in a coil can cause coil collapse. The need to avoid undue lubricity in a passivate coating must also be balanced against the need to provide a formable surface. The passivate coating on the lengths of sheet metal must be sufficiently lubricious, formable and flexible to allow forming of the sheet metal without galling or binding.

As a result of their excellent properties, zinc- and/or aluminum-containing metal surfaces, more particularly aluminum-zinc alloy coated steel sheets have found wide application as building materials in the form of roofing and walling materials, in civil engineering applications, e.g., as guard rails, sound insulating barriers, anti-snow fencing, or drainage gullies, as materials for automobiles, domestic appliances, and industrial machinery and, after having been painted, as replacements for painted steel sheets.

Zinc- and/or aluminum-containing metal surfaces, particularly aluminum-zinc alloy coated steel sheets, are used extensively in roofs and walls of commercial buildings. Particularly in warmer climates, it has become increasingly important to reduce the amount of solar energy retained by these structural components, in part to reduce energy costs. When EMR, such as solar energy, strikes a material, the EMR is absorbed, reflected and/or transmitted (if the material is not opaque) through the material. Absorbed EMR can be re-emitted at various wavelengths or can remain as heat to raise the temperature of the material. Interestingly, even a highly reflective material, such as polished metal, e.g. a chrome car bumper, will get very hot in the sun if the material does not re-emit the EMR it has absorbed. The ability to re-emit absorbed EMR is known in the industry as emittance, which ranges from zero to one; one being a theoretical 100% emittance. It has been demonstrated that emittance is a property of the surface of an object rather than the underlying material. For example, the emittance of a metal roof, newly painted white, has been measured at about 0.83; in comparison, the unpainted metal roof was found to have an emittance of only about 0.08 measured according to ASTM C1371-04a (1.0 being ideal emittance). Aluminum-zinc alloy coated steel sheets have good solar reflecting properties, but poor emittance of solar energy that is not reflected. Such non-reflected energy is largely translated into heat in the steel sheets and some of the heat is then transferred to the interior of the building increasing the cost of cooling the interior.

As energy costs increase, the demand for improvements in the EMR reflecting and/or emitting properties of outdoor structures made of zinc- and/or aluminum-containing metal surfaces, such as aluminum-zinc alloy coated steel sheets, has increased. Typically, the corrosion and lubricious coatings of the prior art deposited on aluminum-zinc surfaces provide less than desirable resistance to heating by the electromagnetic radiation of the sun (solar radiation). One commercially available, chromium-containing corrosion protective coating composition provides an emittance of only 0.22 as measured by ASTM C1371-04a. This is better than the untreated metal surface's emittance of 0.06, but still leaves room for improvement.

Corrosion resistant coatings, such as inorganic chromium passivates and organic thin film passivates do not substantially improve emittance. Some non-white paints provide improvements in emittance of solar energy, but at an insufficient rate with increasing film build compared to their tendency to reduce the solar reflectance of the coated surface. Overall, the non-white paints offer a less than desirable trade-off between emittance and reflectance. White paints initially have good solar reflectance and provide improvements in emittance of solar energy, but white paints have other drawbacks. White paints require a series of additional processing steps and tend to highlight any dirt deposition, easily becoming aesthetically displeasing and hiding the desirable appearance of the metal coating. For at least the foregoing reasons, white paint is not used in many market segments for coating metal. Thus, there is a need for a protective coating for aluminum and/or zinc coated steel sheets that improves emittance while avoiding the limitations of paint.

A common means of increasing resistance to heating by the sun is to deposit reflective coatings, such as white paint and the like on the metal surfaces. Solar reflectance is a measure of the solar reflectance of a surface. Solar reflectance is the ratio of the reflected solar radiation flux to the incident flux. ASTM C1549 provides a scale of 0 to 1.0 of solar reflectance, 0 being non-reflective and 1.0 being 100% reflective. Surfaces coated with white paint have achieved a solar reflectance as measured by ASTM C1549 of as high as 0.7, this is not as reflective as the uncoated metal surface, which is about 0.78. The reflectivity of non-white paints varies by color but is often substantially lower than for white paints. A drawback of painting metal surfaces white to improve resistance to electromagnetic heating is the limited life of the paint and the tendency of the paint to stain and age, which reduces solar reflectance. Another drawback of conventional paints is the thickness required. Standard paint thicknesses in the building material industry are about 25 microns. Over a large expanse of surface, such as a roof, this thickness adds significant weight that must be supported, which adds to the overall expense of construction.

Thus there is a need for a corrosion resistant coating for building materials, particularly aluminum-zinc roofing, that reduces heating of the metal substrate by EMR, such as solar energy, by improving emittance and/or solar reflectance. There is also a need for a corrosion resistant coating that provides good emittance and/or solar reflectance at a lower coating thickness than conventional paints.

As such, there is a need for a composition and process for passivating metal surfaces that overcomes at least one constraint in the prior art.

SUMMARY OF THE INVENTION

This invention relates to treatment of a metal article with an aqueous liquid composition that, before and/or during drying of the liquid composition into place on the metal, spontaneously reacts with the metal surface, without any application of electromotive force from an external source, to produce on the metal a coating providing corrosion resistance that is better than the original untreated metal. The resulting coated surface has the additional feature of improved resistance to heating by electromagnetic radiation (EMR) than the original untreated metal article by reflecting and/or re-emitting the energy. More particularly, this invention is related to a composition and process that provide a corrosion protective treatment which also provides to the metal article improved emittance of EMR, such as solar energy, while maintaining the solar reflectance of the underlying metal, such that the surface and the underlying metal remain cooler than the original untreated metal surface when exposed to sunlight. Still more particularly, the metal surface treated is a metal selected from zinc, zinc alloy, aluminum, aluminum alloy, an alloy of zinc and aluminum, or ferrous metal substrate coated with any of the foregoing metals.

It has been found that at least the major object of the invention as stated above can be achieved by treating a substrate having a metal surface with an aqueous liquid passivate composition having dispersed, preferably homogeneously dispersed, therein solid particles which result in a transparent or translucent, preferably clear and colorless, passivate coating, upon drying of the aqueous liquid passivate composition. Desirably, when deposited on a metal surface, the solid particle-containing passivate coating exhibits a solar reflectance that is not significantly reduced as compared to the solar reflectance of the metal surface coated with a similar passivate coating in the absence of the solid particles. In a preferred embodiment, the passivate coating on the metal surface has a solar reflectance of not less than, independently, in increasing order of preference, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 97 or 99 percent of the solar reflectance of the uncoated metal surface.

It is also desirable that the passivate coating on the metal surface exhibits an emittance of at least, independently, in increasing order of preference, 0.70, 0.75, 0.80, 0.85, 0.90, or 0.95.

Suitable solid particles include those solid particles having physical and chemical characteristics resulting in a transparent or translucent passivate coating, which do not interfere with the corrosion resistance provided by the passivate. Preferred particles are oxides of metals and/or metalloids, defined herein as Al, Ga, Ge, As, Se, In, Sn, Sb, Te, and IUPAC groups 2-12 of the periodic table of elements.

Desirably, the solid particles having a mean particle size in nanometers of less than 250; preferred embodiments have particle size of less than 100, particularly preferably less than 30, most preferably less than 10 nm. Independently preferably, the mean particle size ranges in nanometers are from 1-50, most preferably, if only for economy, from 5-35. At least a portion of the transparency of the passivate coating is due to the size of the particles used.

Applicants have found that certain metal and/or metalloid oxide particles that appear white in bulk, produce transparent, colorless passivate coatings, by way of non-limiting example metal and/or metalloid oxide powders. Without being bound by a single theory, it is believed to be desirable that the passivate comprise a metal and/or metalloid oxide powder selected from the group of metal and/or metalloid oxide powders having high mean emittance of EMR in the 250 to 2500 nm range.

While application of the invention may be through any commercial passivate, Applicants preferred embodiments include chrome (VI) based passivates and alternative embodiments which are substantially chrome-free, as will be described in more detail hereinafter.

FIRST EMBODIMENT

In a first embodiment of the invention, an essentially or substantially chromium-free composition and process for passivating metal surfaces has been developed that provides corrosion resistance comparable to, i.e. about the same as, previously used chromate-containing passivating agents. Another aspect of the first embodiment of the invention provides a new thin organic coating that reduces the tendency of surfaces of coiled or stacked metal sheet metal that are in contact with each other to stick together, i.e. reduces the tendency of the coil or stack to “bind”. In another aspect of first embodiment of the invention, thin organic coating is provided that has sufficient lubricity to enhance formability and prevent binding, but not so much that the lubricity contributes to the tendency of coils of metal to collapse due to sliding of metal surfaces, relative to each other within the coil.

The compositions of the first embodiment of the invention have been developed as chrome-free passivates that desirably perform as well as, and in some aspects better than, chrome containing passivates of the prior art. Although not preferred, formulations according to the invention can be made including chromium. Compositions according to the first embodiment of the invention desirably contain less than 0.04, 0.02, 0.01, 0.001, 0.0001, 0.00001, 0.000001 percent by weight of chromium, most preferably essentially no chromium. It is particularly preferred that the compositions according to the first embodiment contain less than 0.04, 0.02, 0.01, 0.001, 0.0001, 0.00001, 0.000001 percent by weight of hexavalent chromium, most preferably essentially no hexavalent chromium. The amount of chromium present in the compositions of the first embodiment of the invention is desirably minimized and preferably only trace amounts are present, most preferably no chromium is present.

In one aspect, the first embodiment of the invention provides a composition useful for passivating a metal surface, that includes less than 0.04 wt % chromium, preferably essentially no chromium, most preferably in the absence of chromium, and comprising, preferably consisting essentially of, most preferably consisting of water and:

    • (A) at least one inorganic oxide in dispersed form, the particles preferably having a mean particle size of less than 100 nm;
    • (B) at least one complex fluoride of an element selected from the group consisting of Ti, Zr, Hf, Si, Sn, Al, Ge and B; preferably Ti and/or Zr;
    • (C) a non-ionic or non-ionically stabilized resin in dispersed form selected from the group consisting of acrylic, polyurethane, vinyl, and polyester resins, and mixtures thereof;
    • (D) optionally, dissolved phosphate anions;
    • (E) optionally, at least one component comprising vanadium;
    • (F) optionally, at least one wax in dispersed form;
    • (G) and optionally, at least one further additive selected from the group consisting of a sequestrant, a wetting agent, a defoamer, and a pH adjusting component;
      wherein said composition comprises less than 0.04 wt % chromium, and is preferably essentially free of chromium.

In a further embodiment of the invention the total concentration of the complex fluoride is at least 0.5 g/L and is not more than 100 g/L. In a particular aspect of the first embodiment, the composition is essentially free of chromium, (C) comprises a non-ionic or non-ionically stabilized acrylic and/or acrylic copolymer resin in dispersed form, said composition comprising at least one pH adjusting component and/or dissolved phosphate anions, alternatively, the non-ionic or non-ionically stabilized resin is selected from acrylic resins and polyurethane resins, and mixtures thereof.

In another aspect, the first embodiment of the invention provides a composition having a pH within a range of from about 1 to about 5 and the composition is storage stable at 100 deg. F. for at least 3 months, preferably at least 6 months.

In another aspect of the first embodiment, the composition includes at least one wax, selected from the group of waxes stable in strong acidic solutions having an average particle size less than about 1 micron and a melting point of from about 50 to about 175 degrees C. In a yet further aspect of the first embodiment of the invention, the concentration of wax ranges from about 0.05 to about 6 weight percent.

In an alternative version of the first embodiment, the composition includes at least one component that comprises vanadium. In one aspect of this embodiment, a composition useful for passivating a metal surface is provided comprising less than 0.04 wt % chromium and comprising: water; 0.05-10 weight % of at least one complex fluoride of an element selected from the group consisting of Ti, Zr, Hf, Si, Sn, Al, Ge and B; preferably Ti and/or Zr; a non-ionic or non-ionically stabilized resin in dispersed form, said resin selected from the group consisting of acrylic, polyurethane, vinyl, and polyester resins, and mixtures thereof; 25 to 80 weight % of at least one inorganic oxide in dispersed solid form, the solid particles preferably having a mean particle size of less than 50 nm; 0.1 to 7 weight % of at least one component comprising vanadium; 0.05-20 weight % of at least one wax in dispersed form; and optionally, any one or more of the following: dissolved phosphate anions; at least one further additive selected from the group consisting of a sequestrant, a wetting agent, a defoamer, and a pH adjusting component. It is preferred that this coating, upon drying on a metal surface, forms a transparent or translucent coating having an emittance of at least 0.7 and a reflectivity that is at least 50% of the reflectivity of the metal surface uncoated. In a further aspect of this embodiment, (C) comprises 5-50 weight % of a non-ionic or non-ionically stabilized resin in dispersed form selected from the group consisting of acrylic resins and polyurethane resins, and mixtures thereof.

SECOND EMBODIMENT

In a second embodiment the composition comprises, preferably consists essentially of, or more preferably consists of, water and the following components:

    • (A) dispersed solid particles of metal and/or metalloid oxide, desirably the metal and/or metalloid oxide is a powder the particles preferably having a mean particle size of less or equal to 100 nm, and
    • (B) dissolved, dispersed, or both dissolved and dispersed hexavalent chromium that is not part of immediately previously recited component (A);
    • (C) dissolved, dispersed, or both dissolved and dispersed organic film-forming resin;
      and, optionally, one or more of the following components:
    • (D) dissolved, dispersed, or both dissolved and dispersed pH adjusting agent that is not part of any one of immediately previously recited components (A) through (C);
    • (E) dissolved, dispersed, or both dissolved and dispersed trivalent chromium that is not part of any one of immediately previously recited components (A) through (D);
    • (F) dissolved, dispersed, or both dissolved and dispersed wax that is not part of immediately previously recited component (A) through (E);
    • (G) at least one dissolved, dispersed, or both dissolved and dispersed surfactant and/or antiblocking agent that is not part of any of immediately previously recited components (A) through (F);
    • (H) dissolved organic solvent that is not part of any of immediately previously recited components (A) through (G);
    • (I) dissolved, dispersed, or both dissolved and dispersed material selected from the group consisting of (i) reducing agents that are capable, at a specified temperature, of reducing hexavalent chromium in the composition to trivalent chromium and (ii) oxidation products from a reducing agent that has reduced some initially hexavalent chromium in the composition to trivalent chromium, said dissolved, dispersed, or both dissolved and dispersed material not being part of any of immediately previously recited components (A) through (H); and
    • (J) dissolved, dispersed, or both dissolved and dispersed colorant that is not part of any of immediately previously recited components (A) through (I).

In a different aspect of the invention, which applies to both chrome and non-chrome embodiments, a process of treating a ferriferous, aluminiferous or zinciferous metal substrate is provided comprising: optionally, cleaning a surface of said metal substrate to be passivated; contacting the metal substrate surface to be passivated with a passivating composition as described herein for a time sufficient to form a coating on said metal surface and drying the coating. This process may include the step of coating the metal substrate with a dissimilar metal, thereby creating a metal substrate surface to be passivated, prior to contacting with the passivating composition. Optionally, a process according to the invention may include a step wherein the passivating coating on the metal surface is overcoated with a protective layer comprising at least one organic binder.

Various embodiments of the invention include working compositions for direct use in treating metals, make-up concentrates from which such working compositions can be prepared by dilution with water, replenisher concentrates suitable for maintaining optimum performance of working compositions according to the invention, processes for treating metals with a composition according to the invention, and extended processes including additional steps that are conventional per se, such as cleaning, rinsing, and subsequent painting or some similar overcoating process that puts into place an organic binder-containing protective coating over the metal surface treated according to one embodiment of the invention. Articles of manufacture including surfaces treated according to a process of the invention are also within the scope of the invention.

Except in the operating examples, or where otherwise expressly indicated, all numerical quantities in this description indicating amounts of material or conditions of reaction and/or use are to be understood as modified by the word “about” in describing the broadest scope of the invention. Practice within the numerical limits stated is generally preferred. Also, unless expressly stated to the contrary: percent, “parts of”, and ratio values are by weight; the term “polymer” includes “oligomer”, “copolymer”, “terpolymer”, and the like; the description of a group or class of materials as suitable or preferred for a given purpose in connection with the invention implies that mixtures of any two or more of the members of the group or class are equally suitable or preferred; description of constituents in chemical terms refers to the constituents at the time of addition to any combination specified in the description, and does not necessarily preclude chemical interactions among the constituents of a mixture once mixed; specification of materials in ionic form implies the presence of sufficient counter-ions to produce electrical neutrality for the composition as a whole (any counter-ions thus implicitly specified should preferably be selected from among other constituents explicitly specified in ionic form, to the extent possible; otherwise such counter-ions may be freely selected, except for avoiding counter-ions that act adversely to the objects of the invention); the first definition of an acronym or other abbreviation applies to all subsequent uses herein of the same abbreviation and applies mutatis mutandis to normal grammatical variations of the initially defined abbreviation; the term “paint” includes all like materials that may be designated by more specialized terms such as lacquer, enamel, varnish, shellac, topcoat, and the like; and the term “mole” and its variations may be applied to elemental, ionic, and any other chemical species defined by number and type of atoms present, as well as to compounds with well defined molecules. For the purposes of this description, unless specifically stated otherwise:

  • a “dissolved, dispersed, or both dissolved and dispersed film-forming resin” means a material that satisfies the following condition: when said liquid film is dried at at least one temperature that is at least 40° C., the resin forms a cohesive continuous solid body at the temperature of drying after drying is complete; and
  • “wax” is defined as a substance that: (i) is a plastic solid at 25° C. under normal atmospheric pressure and (ii) melts in contact with the natural ambient atmosphere without visually evident decomposition at a temperature that is at least 55° C.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to compositions and methods of the invention, which constitute the best modes of practicing the invention presently known to the inventors.

Applicants have developed a process for coating a substrate having a metal surface with an aqueous liquid passivate composition having dispersed, preferably homogeneously dispersed, therein solid particles which result in a transparent or translucent, preferably clear and colorless, passivate coating, upon drying of the aqueous liquid passivate composition. The passivate coating provides resistance to heating to the underlying metal surface by a two-fold mechanism. First, the coating has high emittance in the EMR wavelengths that are known in the art to cause the most heating, namely about 250 to about 2500 nm. This range of wavelengths includes light visible to humans and the near infrared spectrum. The high emittance of the coating is important to heat resistance particularly since metals tend to have high reflectance and poor emittance. The second aspect of the mechanism uses the transparency of the passivate coating to gain the benefit of the solar reflectance of the underlying metal. Thus the coating improves the emittance of the coated metal substrate while minimizing any negative effect on the metal's solar reflectance. Preferably, the passivate coating on the unpainted metal surface provides a material that exhibits a solar reflectance of 0.65, 0.66, 0.67, 0.68, 0.69, 0.70, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.80, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99 or 1.00. and an emittance 0.55, 0.60, 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.69, 0.70, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.80, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99 or 1.00.

All embodiments of the passivate coatings described herein comprise solid particles. Suitable solid particles include those solid particles having physical and chemical characteristics resulting in a transparent passivate coating, which do not interfere with the corrosion resistance provided by the passivate. Preferred particles are oxides of metals and/or metalloids, defined herein as Al, Ga, Ge, As, Se, In, Sn, Sb, Te, and IUPAC groups 2-12 of the periodic table of elements. In a preferred embodiment, the solid particles are selected from oxides of Ti, Zn, Zr, Sb, Al, Hf, and V, most preferably Ti, Zr and Sb.

Desirably, the solid particles having a mean particle size of less than or equal to, independently, in increasing order of preference, of 100, 80, 60, 50, 40, 35, 30, 25, 20, 15, 10, or 6 nm. At least a portion of the transparent or translucent nature of the passivate coating is due to the size of the particles used. Significant quantities of particles larger than 100 nm, typically used in conventional paints, result in an opaque surface that interferes with the underlying metal surface's reflection of solar energy out through the coating.

Typical substances useful as solid particle additives are those oxides that are solid at ambient temperature and are substantially insoluble in water, as will be understood by one of skill in the art. Desirably, these substances are oxides of metals and/or metalloids. In one embodiment, the raw material metal and/or metalloid oxide particles in bulk have a white appearance to the human eye.

Applicants have found that certain metal and/or metalloid oxide particles produce transparent, colorless passivate coatings, by way of non-limiting example metal and/or metalloid oxide powders. Without being bound by a single theory, it considered desirably, that the emittance of the bulk, dry raw material metal and/or metalloid oxide powder also has a mean emittance of EMR in the 250 to 2500 nm range that is at least, independently, in increasing order of preference, 0.60, 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.69, 0.70, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.80, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99 or 1.00.

Accordingly, one or more inorganic oxides are present in the passivate composition, preferably in dispersed, fine particulate form. Oxides of silicon, aluminum, zinc and the like may be used, for example. In one embodiment, when one or more components comprising inorganic oxides are used, independently of their chemical nature, the total concentration of inorganic oxides in a working composition according to the invention, preferably is at least, with increasing preference in the order given, 10.0, 20.0, 25.0, 30.0, 35.0, 40.0, 45.0, 50.0, 55.0, 60.0 weight % of total composition and independently preferably not more than, with increasing preference in the order given, 80.0, 75.0, 74.0, 73.0, 72.0, 71.0, 70.0, or 65.0 weight %. In a preferred embodiment, the weight percent of oxides is in the range of 20%-75%, most preferably 30%-65%. LUDOX CL-P silica, available from W. R. Grace & Co., Bonderite NT-1, available from Henkel Corporation, and Nyacol DP 5370, a commercially available aqueous dispersion of nanoparticulate zinc oxide, are illustrative inorganic oxides suitable for use in the present invention.

In a preferred embodiment, the amount and particle size of oxide component is selected such that the as-dried coating according to the invention is a clear, colorless coating after not more than, with increasing preference in the order given 60, 45, 30, 21, 14, 7, 5, 3, 2 or 1 days.

FIRST EMBODIMENT

Typically, thin-film organic passivates comprise an organic film forming resin; a surface passivating material; water and optional additives. One of the problems associated with formulations with non-chrome passivating materials in such formulations is the degree to which the non-chrome passivating materials compromise stability in the formulated thin-film passivating composition. Many alternative passivating materials, such as organic and inorganic acids, are most effective when the formulated thin-film passivating composition is at low pH. Under these conditions most resin dispersions or latexes are destabilized, i.e. the resin does not remain dispersed. Two indicators of instability in the composition are phase separation, including precipitation, which is not readily remixed, and coagulation, where the composition may form a consistency similar to, and known in the industry as, “cottage cheese”. Prior art approaches have not provided stable formulations. Such systems either phase separated immediately upon mixing, or separated upon aging at elevated temperature.

It has now been found that using a resin which is non-ionic or non-ionically stabilized provides passivates according to the invention which are stable both immediately after preparation at room temperature, as well as after aging at elevated temperature for several months. Moreover, such compositions can provide corrosion protection to metal surfaces that is at least comparable to that attained using chrome-containing passivates.

Storage-stable organic passivate formulations are obtained when the organic film forming resin is non-ionic or is non-ionically stabilized. The non-ionically stabilized resins of the invention can be stabilized by conventional non-ionic surfactant or by incorporating covalently-bound non-ionic stabilizing groups into the polymer chain of the resin. Compositions according to the invention are stable and do not coagulate upon mixing of the components together. Desirably, the compositions remain dispersed in a single phase, or if phase separation occurs, can be readily remixed. It is preferred that the compositions do not form precipitates or coagulate upon storage for at least, with increasing preference in the order given, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23 or 24 weeks. It is independently preferred that the compositions do not form precipitates or coagulate upon storage at ambient or higher temperatures including, with increasing preference in the order given, 80, 85, 90, 95, 100 and 110 degrees F. Particularly preferred embodiments of the present invention are stable after aging at elevated temperature, e.g. 100 degrees F., for at least six months.

It has been found that one or more of the objects stated above for the invention can be achieved by the use of a passivating aqueous liquid composition, as described herein. The present invention thus provides a composition useful for passivating a metal surface, said composition comprising, preferably consisting essentially of, most preferably consisting of water and:

    • (A) at least one inorganic oxide in dispersed form;
    • (B) at least one complex fluoride of an element selected from the group consisting of Ti, Zr, Hf, Si, Sn, Al, Ge and B;
    • (C) a non-ionic or non-ionically stabilized resin in dispersed form said resin selected from the group consisting of acrylic, polyurethane, vinyl, and polyester resins, and mixtures thereof;
    • (D) optionally, dissolved phosphate anions;
    • (E) optionally, at least one component comprising vanadium;
    • (F) optionally, at least one wax in dispersed form;
    • (G) and optionally, at least one further additive selected from the group consisting of a sequestrant, a wetting agent, a defoamer, and a pH adjusting component;
      wherein said composition comprises less than 0.04 wt % chromium, and is preferably essentially free of chromium.

The compositions of the first embodiment of the invention contain, in addition to water, at least one complex fluoride of an element selected from the group consisting of Ti, Zr, Hf, Si, Sn, Al, Ge and B (preferably, Ti, Zr and/or Si; most preferably, Ti). The complex fluoride should be water-soluble or water-dispersible and preferably comprises an anion comprising at least 4 fluorine atoms and at least one atom of an element selected from the group consisting of Ti, Zr, Hf, Si, Sn, Al, Ge or B. The complex fluorides (sometimes referred to by workers in the field as “fluorometallates”) preferably are substances with molecules having the following general empirical formula (I):
HpTqFrOs (I)
wherein each of p, q, r, and s represents a non-negative integer; T represents a chemical atomic symbol selected from the group consisting of Ti, Zr, Hf, Si, Sn, Al, Ge, and B; r is at least 4; q is at least 1 and preferably is not more than, with increasing preference in the order given, 3, 2, or 1; unless T represents B, (r+s) is at least 6; s preferably is not more than, with increasing preference in the order given, 2, 1, or 0; and (unless T represents Al) p is preferably not more than (2+s), with all of these preferences being preferred independently of one another. One or more of the H atoms may be replaced by suitable cations such as ammonium, metal, or alkali metal cations (e.g., the complex fluoride may be in the form of a salt, provided such salt is water-soluble or water-dispersible).

The acids are usually preferred for economy and because a net acidity of the compositions is preferable as considered further below, and the entire stoichiometric equivalent as any of the above recited fluorometallate ions in any source material as dissolved in a composition according to the invention or a precursor composition for it is to be considered as part of the fluorometallate component, irrespective of the actual degree of ionization that may occur. Independently of their chemical nature, the total concentration of the fluorometallate anions dissolved in a working treatment composition according to the invention preferably is at least, with increasing preference in the order given, 0.5, 1.0, 2.0, 2.5, 3.0, 4.0, 5.0, 6.0, 7.5, 8.5, 10.0, 11.0, 12.0 or 13.0 g/L and independently, primarily for reasons of economy, preferably is not more than, with increasing preference in the order given, 400, 200, 100, 90, 80, 75, 65, 50, 45, 38, 37.5, 35.0, 32.5 30.0, 28.0, 27.0 or 26.0 g/L.

Illustrative examples of suitable complex fluorides include, but are not limited to, H2TiF6 (which is especially preferred), H2ZrF6, H2HfF6, H2SiF6, H2GeF6, H2SnF 6, H3AlF6, ZnSiF6, and HBF4 and salts (fully as well as partially neutralized) and mixtures thereof. Examples of suitable complex fluoride salts include SrSiF6, MgSiF6, Na2SiF6 and Li2SiF6.

The dissolved phosphate ions that comprise component may be obtained from a variety of sources as known in the art. Normally much of the phosphate content will be supplied by phosphoric acid added to the composition, and the stoichiometric equivalent as phosphate ions of all undissociated phosphoric acid and all its anionic ionization products in solution, along with the stoichiometric equivalent as phosphate ions of any dihydrogen phosphate, monohydrogen phosphate, or completely neutralized phosphate ions added to the composition in salt form, are to be understood as forming part of phosphate ions, irrespective of the actual degree of ionization and/or reaction to produce some other chemical species that exists in the composition. If any metaphosphoric acid, other condensed phosphoric acids, or salts of any of these acids are present in the compositions, their stoichiometric equivalent as phosphate is also considered part of the phosphate component. Generally, however, it is preferred, at least partly for reasons of economy, to utilize orthophosphoric acid and its salts as the initial source for the phosphate component.

In a working passivating aqueous liquid composition according to this embodiment of the invention, the concentration of phosphate ions and/or their stoichiometric equivalents as noted above preferably is at least, with increasing preference in the order given, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 9.0, 10.0, 12.0, 13.0, 14.0, 15.0, 16.0 or 17.0 grams per liter (hereinafter usually abbreviated as “g/L”) of total composition and independently preferably is not more than, with increasing preference in the order given, 400, 200, 100, 90, 80, 75, 70, 60, 50, 45, 40 or 34 g/L.

Furthermore, independently of their actual concentrations, the concentrations of fluorometallate anions and phosphate ions preferably are such that the ratio between them, in working compositions and concentrated solutions used to prepare working concentrations, is at least, with increasing preference in the order given, 0.10:1.0, 0.15:1.0, 0.25:1.0, 0.35:1.0, 0.45:1.0, 0.50:1.0, 0.55:1.0, 0.60:1.0, 0.65:1.0, or 0.75:1.0 and independently preferably is not more than, with increasing preference in the order given, 5:1.0, 4:1.0, 3.5:1.0, 3.2:1.0, 2.0:1.0, 1.5:1.0, 1.0:1.0, or 0.9:1.0.

The resin used in the first embodiment may be either non-ionic or non-ionically stabilized. “Non-ionically stabilized” resins include resins that are stabilized (i.e., kept in dispersed form) using a non-ionic surfactant as well as resins that are stabilized by incorporating covalently-bound non-ionic stabilizing groups onto the resin. Preferably, the number of anionic functional groups on the resin is minimized, as this will tend to improve the stability of the dispersed resin under acidic conditions. These resins can be described as aqueous emulsions or dispersions. They can be high molecular weight emulsions such as acrylic latex, polyurethane dispersion, or vinyl latex or they can be low molecular weight dispersions including water reducible polyester, acrylic, or urethane. The resins may be copolymers or mixtures of polymer chains having similar or different functional groups.

These resins can be either thermoplastic or thermosetting. Reactive functionality is any functionality that can react with an external curing agent (two component system) or internal curing agents (one component system). Reactive functionality is acceptable in resins useful in the invention provided that the amount of reactive functionality does not adversely affect the stability of the resulting composition.

The concentration of resin (measured on a solids basis) in the passivate compositions of the first embodiment of the invention preferably is at least, with increasing preference in the order given, 4.0, 5.0, 6.0, 7.0, 9.0, 10.0, 12.0, 13.0, 14.0, 15.0, 16.0 or 17.0 weight % (hereinafter usually abbreviated as “g/L”) of total composition and independently preferably is not more than, with increasing preference in the order given, 60, 50, 45, 40, 39, 38, 37, 36, 35, 34, 33, 32, 31, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21 weight %. The optimal amount of resin depends in large part on the desired end property of the coating. If relatively significant corrosion protection is considered more important than ease of coating removability, then a relatively higher amount of resin can be used, however, if ease of coating removability is considered more important than corrosion protection, then a relatively smaller amount of resin can be used.

Furthermore, in the first embodiment, independently of their actual concentrations, the concentrations of resin and phosphate anions preferably are such that the ratio between them, in working compositions and concentrated solutions used to prepare working concentrations, is at least, with increasing preference in the order given, 0.005:1.0, 0.01:1.0, 0.015:1.0, 0.02:1.0, 0.025:1.0, 0.03:1.0, 0.035:1.0, 0.04:1.0, 0.045:1.0 or 0.05:1.0, and independently preferably is not more than, with increasing preference in the order given, 3.:1.0, 2.5:1.0, 2.0:1.0, 1.5:1.0, 1.3:1.0, 1.2:1.0, 1.0:1.0, 0.90:1.0, 0.75:1.0, 0.60:1.0, 0.50:1.0, 0.45:1.0, 0.35:1.0, 0.25:1.0, 0.20:1.0, 0.10:1.0 or 0.07:1.0.

Preferred resins for use in the first embodiment include acrylic resins and polyurethane resins. Acrylic resins are well-known in the art and are thermoplastic synthetic organic polymers made by the polymerization of ethylenically unsaturated monomers selected from groups consisting of acrylates, methacrylates, styrene, vinyl, or allylic monomers. Examples of these include monomers such as acrylic acid, methacrylic acid, alkyl esters of acrylates and methacrylates, and the like, including copolymers of such monomers with non-acrylic monomers such as olefins, vinyl compounds, styrene, and the like. Suitable non-ionically stabilized acrylic resin dispersions and latexes are available commercially or may be prepared by known techniques. Suitable acrylic resin based materials include acrylic polymers and acrylic copolymers comprising styrene, acrylates and/or methacrylates. RHOPLEX HA-16 acrylic latex, available from Rohm & Haas, is an example of a commercially available, non-ionically stabilized acrylic resin latex useful in the present invention. RHOPLEX HA-16 is believed to be a high molecular weight copolymer of styrene and acrylates and methacrylates.

Polyurethane resins are also well-known in the art and are resins obtained by reacting polyisocyanates with one or more active hydrogen-containing compounds such as polyether, polyester, polycarbonate, polyacrylic, or polyolefin glycols to form a pre-polymer which can be dispersed in water followed by chain extension with polyamines or polyalcohols. The nonionic stabilization of the acrylic or urethane polymers can be achieved by incorporating a reactive internal non-ionic monomer or by the addition of non-ionic surfactant. Suitable non-ionic polyurethane dispersions and latexes are available commercially or may be synthesized using standard methods. PERMAX 120, 200 and 220 emulsions, available from Noveon, Inc., 9911 Brecksville Road, Cleveland, Ohio 44141-3247, are examples of polyurethane resin dispersions found to be especially useful in the present invention. These materials are described by their supplier as aliphatic polyether waterborne urethane polymers constituting about 35-44% solids.

Generally speaking, the effectiveness of the passivate composition in imparting corrosion resistance to a metal surface will be influenced by the pH of the composition. One or more pH adjusting components may be used in compositions according to the invention. The pH of the treatment formulation according to the first embodiment should be from 1.0 to 5.0, more preferably 1.2 to 4.5, and most preferably from 1.5 to 3.0. The pH can be adjusted using a pH adjusting component such as an acid such as phosphoric acid, or nitric acid, or a base such as sodium hydroxide, potassium hydroxide, sodium carbonate, or ammonium hydroxide, with ammonium hydroxide being the most preferred. Generally, acids are added to the composition to lower pH and optimize its effectiveness. Although both organic as well as inorganic acids can be used, generally it will be preferred to use a mineral acid such as a phosphorus-containing acid (e.g., phosphoric acid). The phosphate ions included in certain aspects of the first embodiment of the invention may be derived, in whole or in part from this phosphorus-containing acid.

In one aspect of the first embodiment of the invention, the composition comprises at least one component comprising vanadium. When one or more components comprising vanadium are used, independently of their chemical nature, the total concentration of vanadium dissolved in a working composition according to the invention, preferably is at least, with increasing preference in the order given, 0.10, 0.20, 0.25, 0.30, 0.40, 0.50, 0.55, 0.60 or 0.65 weight % of total composition and independently preferably not more than, with increasing preference in the order given, 5.0, 4.0, 3.0, 2.5, 2.0, 1.5, 1.0, 0.90, 0.80 or 0.75 weight %. Preferred sources of vanadium include V2O5 and NH4VO3.

The composition of the present invention also optionally includes a lubricating agent. The lubricating agent is particularly useful for providing lubrication to surfaces that are to be formed, so as to prevent binding and galling. Lubricating agents that improve lubricity of the coating during forming without increasing water sensitivity of the composition and that are soluble and stable in strong acidic solutions are preferred. Moreover, for use in the coil industry it is desirable that the lubricity provided to the surfaces for subsequent forming does not interfere with stable coiling of the substrate for transport or storage. It is desirable that the lubricating agent is a wax emulsion to aid in dispersal in the composition. Such cares can function as a release aid in the coating formed on the metal surface upon application of the passivate composition, lower the coefficient of friction on the metal surface, improve metal forming, and/or provide anti-block properties. Examples of suitable waxes include Fischer Tropsch waxes, polyethylene waxes (including LDPE and HDPE waxes), paraffin waxes, montan waxes, carnauba wax, ethylene/acrylic acid copolymer waxes, polypropylene waxes, microcrystalline waxes, and the like, and combinations thereof. In one embodiment, polypropylene and paraffin comprise the lubricating agent. Typically, the wax will have an average particle size less than about 1 micron and a melting point of from about 50 to about 175 degrees C.

The concentration of wax in a passivate composition according to the invention preferably is at least, with increasing preference in the order given, 0.5, 1.0, 2.0, 2.5, 3.0, 4.0, 5.0, 6.0, 7.5, 8.5, 10.0, 11.0, 12.0 or 13.0 g/L and independently, primarily for reasons of economy, preferably is not more than, with increasing preference in the order given, 200, 100, 90, 80, 75, 65, 50, 45, 38, 37.5, 35.0, 32.5 30.0, 28.0, 27.0 or 26.0 g/L.

The passivate composition may also comprise a sequestrant (i.e., sequestering agent). Sequestrants containing two or more phosphonic acid groups per molecule may be used, including, for example, 1-hydroxy ethylidene-1,1-diphosphonic acid (available commercially under the trademark DEQUEST 2010 from Solutia Inc., 575 Maryville Centre Drive, St. Louis, Mo. The sequestrant concentration in the passivate composition may range, for example, from about 0.1 to about 10 weight percent, and preferably is at least, with increasing preference in the order given, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11.0, 12.0 or 13.0, 14.0, 15.0, 16.0, 17.0, 18.0, 19.0, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30 g/L and independently, primarily for reasons of economy, preferably is not more than, with increasing preference in the order given, 90, 80, 75, 65, 64, 63, 62, 61, 60, 59, 58, 57.5, 55.0, 52.5, 50.0 g/L.

The composition of the present invention also optionally includes a wetting agent. The wetting agent is particularly useful for wetting surfaces that are known to be somewhat difficult to wet, such as Galvalume®. Wetting agents that improve coating wetting without increasing water sensitivity of the composition and that are soluble and stable in strong acidic solutions are preferred. Examples of suitable wetting agents include, but are not limited to, phosphate esters and silicon based wetting agents. Byk 348, a wetting agent commercially available from Byk Chemie, is a silicon surfactant based on the polyether modified poly-dimethyl-siloxane. Preferred phosphate esters include, but are not limited to, substituted phosphate esters, and more preferably substituted carboxylated phosphate esters.

When one or more wetting agents are used, independently of their chemical nature, the total concentration of wetting agent dissolved in a working composition according to the invention, preferably is at least, with increasing preference in the order given, 0.10, 0.20, 0.25, 0.30, 0.40, 0.50, 0.55, 0.60 or 0.65 g/L of total composition and independently preferably not more than, with increasing preference in the order given, 5.0, 4.0, 3.0, 2.5, 2.0, 1.5, 1.0, 0.90, 0.80 or 0.75 g/L.

The passivate composition may also comprise a defoamer, i.e. a defoaming agent. Suitable defoamers are those known defoamers, which do not adversely affect the stability of the composition. In particular, the defoamer desirably is compatible with the resins used. Defoamers containing hydrocarbons and/or non-ionic surfactants may be used, including, for example, Foamaster® NDW (available commercially from Cognis Inc. The defoamer concentration in the passivate composition is not critical provided that sufficient defoaming agent is provided to reduce foaming of the composition, for example, from about 0.01 to about 0.4 weight percent, preferred is 0.02%, depending on the process conditions.

SECOND EMBODIMENT

In the second embodiment, a hexavalent chromium containing passivate that provides both excellent corrosion resistance and improved resistance to retention of solar radiation is described. Accordingly, the second embodiment of the invention relates to compositions and processes for passivating metal surfaces, which also improves the metal surface's resistance to heating by electromagnetic radiation (hereinafter EMR), in particular solar radiation or energy. This embodiment is applicable to aluminiferous and/or zinciferous surfaces which differ from the underlying metal, as well as to solid alloys of aluminum and/or zinc which include zinc, such as hot-dip and electro-galvanized, zinc alloys, aluminum, aluminum alloys and mixtures thereof, as well as steel coated with these metals.

The second embodiment comprises oxides of metals and/or metalloids, as described herein, which provide a surprising benefit of improved emittance of absorbed solar radiation while retaining more than 50% of the reflectance of the uncoated metal. Preferred embodiments of the passivate coating are transparent or translucent and colorless.

Any water soluble source of hexavalent chromium atoms may be used to provide component (B) according to the invention. Examples include chromic acid (i.e., CrO3), ammonium bichromate, potassium bichromate, sodium bichromate, ammonium chromate, potassium chromate, sodium chromate, and the like. The use of ammonium salts and/or chromic acid is preferred, in order to avoid the presence in a composition according to the invention of any non-volatile alkali component. Inasmuch as the pH value preferred for a working composition according to the invention is at least slightly alkaline, ammonium salts are preferred for at least part of component (B), but they are, at least for economy, preferably formed in situ by adding aqueous ammonia to an aqueous solution of chromic acid. Accordingly, the concentration of chromium in a composition according to the invention is usually measured as its stoichiometric equivalent as CrO3, and this stoichiometric equivalent preferably has a ratio to the concentration of component (C) (on a dry basis) in the same composition that is at least, with increasing preference in the order given, 0.0001:1.0, 0.0005:1.0, 0.0010:1.00, 0.0020:1.00, 0.0050:1.00, 0.0075:1.00, 0.0100:1.00, 0.0110:1.00, 0.0120:1.00, 0.0130:1.00, 0.0135:1.00, 0.0140:1.00, 0.0145:1.00, 0.0150:1.00, 0.0155:1.00, 0.0158:1.00, or 0.0162:1.00 and independently preferably is not more than, with increasing preference in the order given, 0.50:1.00, 0.20:1.00, 0.10:1.00, 0.050:1.00, 0.040:1.00, 0.030:1.00, 0.025:1.00, 0.021:1.00, or 0.017:1.00. If the hexavalent chromium-containing material is too low in ratio to organic film-forming resin, the treated material usually has inadequate corrosion resistance and is often subject to blackening, while if the ratio of hexavalent chromium to organic film-forming resin is too large, the treatment composition may become unstable, will definitely generate higher pollution and/or pollution abatement costs if used in the large majority of jurisdictions where chromium is considered polluting, and will decrease the likelihood of achieving a transparent coating as is usually desired.

Component (C) preferably is selected from resins that, after drying from any solution/dispersion in which they may initially be present, are not soluble in water at 25° C. to an extent greater than, with increasing preference in the order given, 1.0, 0.5, 0.20, 0.10, 0.050, 0.020, 0.010, 0.0050, 0.0020, 0.0010, 0.00050, 0.00020, or 0.00010 % of the resin in water.

Independently, component (C) preferably is selected from organic film-forming polymers of vinyl monomers selected from the group consisting of hydrocarbons, halohydrocarbons, acrylic acid, methacrylic acid, maleic acid, and all esters, amides, and nitrites of organic acids. (Whether before or after polymerization, salts of any of these acids are to be understood as equivalent to the acids themselves.) If these polymers, as is usually preferred, have as low a solubility in water before drying as they are preferred to have after drying, the resins will be predominantly dispersed rather than dissolved in the treatment composition. In such dispersions, a surfactant is normally used as a dispersing agent. The surfactants commonly used for this purpose in some (but not all) commercially supplied latexes, the preferred source for component (C), have not been observed to have any harmful effect on the properties of the compositions prepared with latexes containing them and if present are part of optional component (G) as described above, unless they are copolymerized into the polymer resin itself, in which instance they are part of component (C).

More preferably, component (C) is selected from polymers of monomers selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, the esters of all of these acids, acrylonitrile, methacrylonitrile, acrylamide, and methacrylamide and still more preferably, in such polymers, the total number of millimoles of carboxylic acid and carboxylate salt moieties per gram of the dried resin is at least, with increasing preference in the order given, 0.030, 0.040, 0.050, 0.070, 0.080, 0.090, 0.100, 0.110, 0.120, 0.130, 0.135, or 0.140 and independently preferably is not more than, with increasing preference in the order given, 1.5, 1.0, 0.50, 0.40, 0.35, 0.30, 0.27, 0.24, 0.22, 0.200, 0.190, 0.180, 0.170, or 0.160.

Independently of other preferences, polymers of component (C) preferably have a glass transition temperature that is not more than, with increasing preference in the order given, 30, 27, 25, 23, 21, 19, 17, or 15° C.

A working treatment composition according to the invention preferably has a pH value that is at least, with increasing preference in the order given, 5.0, 5.5, 6.0, 6.5, 7.0, 7.2, 7.4, or 7.6, and independently preferably is not more than, with increasing preference in the order given, 10.0, 9.6, 9.2, 9.0, 8.8, 8.6, 8.4, 8.2, 8.0, 7.8. If the pH is too high or too low, the composition is likely to be unstable, because of precipitation and/or coagulation of at least part of its constituents. If most or all of the chromium present has been added as CrO3 and there is no other alkaline constituent in the composition, an alkalinizing agent will usually be required as optional component (D) in order to achieve a pH value of 7.5 or more when that is desired. Any alkaline material may be used, but volatile ones such as ammonia and amines, for example, monoethylamine, diethylamine, triethylamine, and the like, and alkanolamines such as monoethanolamine, diethanolamine, and triethanolamine are preferred. At least for economy, simple ammonia, usually added as a concentrated solution in water, is most preferred.

Chemically, a wax to be used as optional component (F) in a composition or process according to this invention preferably is predominantly an organic substance selected from the group consisting of hydrocarbons, halohydrocarbons, halocarbons, alcohols, ethers, carboxylic acids, esters of carboxylic acids, ketones, and aldehydes. Most if not all of the preferred waxes have scant solubility in water, and therefore are preferably added as dispersions to a mixture that constitutes, or after further additions will constitute, a composition according to the invention. Commercially available dispersions with fine dispersed particle size are preferably used. More particularly, the average particle size of a dispersion of wax that is part of component (F) in a composition according to the invention preferably is not more than, with increasing preference in the order given, 50, 40, 30, 20, 10, 5, 2, 1.0, 0.5, 0.20, 0.15, 0.12, 0.10, 0.08, or 0.06 micrometers. As with the organic film-forming resin polymers used in the same compositions, there is usually a dispersing agent required for a stable dispersion of this type; the dispersing agents in some but not all commercially supplied dispersions do not have any detrimental effect on a composition or process according to the invention; and when a dispersing agent for the wax component in a composition used according to the invention is present, this dispersing agent usually forms part of optional component (G).

Independently of its chemical nature, the melting point of a wax used in this invention preferably is at least, with increasing preference in the order given, 57, 65, 75, 85, 95, 105, 110, 115, 120, 125, or 130° C. and independently preferably is not more than, with increasing preference in the order given, 400, 350, 300, 250 200, 180, 170, 160, 155, 150, 145, 140, or 135° C.

A wax component (F) may be used to obtain the maximum resistance to damage in forming the finished product, but too large a fraction of wax can be disadvantageous. For example, too much wax may: reduce the corrosion resistance, if the wax by itself does not form a continuous protective coating as component (C) does; make a substrate surface so slippery that it is very difficult to keep it coiled and/or to keep anything placed on an inclined surface of the coated substrate from sliding off; and/or cause undesired adhesion of the coated surface to another surface with which it is in contact, especially if the wax is low in melting point and the coated surface is exposed to heat while or shortly before it is in contact with another surface from which it is desired later to separate it. Specifically, the ratio by mass, on a dried basis, of wax component (F) to component (C) preferably is at least, with increasing preference in the order given, 0.020:1.00, 0.040:1.00, 0.050:1.00, 0.060:1.00, 0.065:1.00, 0.070:1.00, 0.075:1.00, 0.080:1.00, 0.085:1.00, 0.090:1.00, 0.095:1.00, 0.100:1.00, or 0.103:1.00 and independently preferably is not more than, with increasing preference in the order given, 0.50:1:00, 0.40:1.00, 0.30:1.00, 0.25:1.00, 0.20:1.00, 0.15:1.00, 0.13:1.00, or 0.11:1.00.

As already noted above, some surfactant, part of optional component (G), may be needed to disperse any insufficiently water-soluble constituents of component (C). If the substrate to be treated is exceptionally difficult to wet uniformly and/or if the composition according to the invention contains preferred amounts of solvent added to reduce the likelihood of cracks in the coating formed, additional surfactant may be needed to assure adequately uniform wetting. In such an instance, a fluorinated surfactant, more preferably a fluorinated anionic surfactant, most preferably a fluorinated alkyl carboxylate salt surfactant in which at least 80% of the carboxylate groups have at least 8 carbon atoms, is preferred. Independently, the concentration of fluorinated surfactant in a working composition according to the invention preferably is at least, with increasing preference in the order given, 0.0010, 0.0020, 0.0030, 0.0040, 0.0050, 0.0060, or 0.0070% of the total composition and independently preferably is not more than, with increasing preference in the order given, 0.080, 0.060, 0.050, 0.040, 0.030, 0.020, 0.015, 0.010, 0.0090, or 0.0080% of the total composition. A surfactant may also be needed in some instances for abatement of foaming, particularly if preferred amounts and types of component (G) as described below are present in the working composition. If foam is a problem with a composition according to the invention that does not contain an antifoam agent, there should be present in the composition according to the invention an amount of antifoam agent corresponding to a concentration that is at least, with increasing preference in the order given, 0.0020, 0.0040, 0.0050, 0.0060, 0.0070, 0.0080, 0.0090, 0.0100, 0.0110, 0.0120, 0.0130, or 0.0140% of the total composition and independently preferably is not more than, with increasing preference in the order given, 0.100, 0.080, 0.060, 0.050, 0.040, 0.030, 0.025, 0.020, 0.018, or 0.016% ofthe total composition. Independently of its concentration, any antifoam agent used preferably is a non-ionic surfactant and more preferably is selected from the group consisting of poly(oxyalkylene) polymers, ethoxylates of organic substances containing at least one phenol moiety per molecule, and organo-siloxane polymers.

An antiblocking agent may be used to reduce spontaneous, at least temporary adhesion between a surface treated according to the invention and another surface, optionally also treated according to the invention, which contacts the surface treated according to the invention. (This phenomenon, often called “blocking”, is particularly troublesome when surfaces treated according to the invention are wound into a coil that is later unwound before use. The compression inherent in winding favors at least temporary adhesion between the surfaces. If such adhesion occurs, unwinding can cause transfer of coating from one portion of the treated surface to some other surface, thereby producing unsatisfactory coating uniformity. Even if such transfer does not occur, “stick-slip” behavior of the coil can occur, resulting in uneven tensions in various parts of the coil processing line and consequent potential coil treatment and/or coil usage irregularities that are undesirable.) It has been found that blocking can be prevented by including in a composition according to the invention at least one of the following types of antiblocking agents:

  • a silicone and/or ethoxylated silicone polymer, preferably a siloxane, in an amount having a ratio to the total solids content of the composition that is at least, with increasing preference in the order given, 0.0010:1.00, 0.0020:1.00, 0.0030:1.00, 0.0040:1.00, 0.0050:1.00, 0.0080:1.00, 0.010:1.00, 0.015:1.00, 0.020:1.00, 0.023:1.00, or 0.025:1.0 and independently, at least for economy, preferably is not more than, with increasing preference in the order given, 1.0:1.00, 0.80:1.00, 0.60:1.00, 0.50:1.00, 0.45:1.00, 0.40:1.00, 0.35:1.00, 0.30:1.00, 0.25:1.00, 0.20:1.00, 0.15:1.00, 0.12:1.00, 0.10:1.00, or 0.075:1.00; and
  • a fluorinated organic surfactant, preferably an anionic surfactant, in an amount having a ratio to the total solids content of the composition that is at least, with increasing preference in the order given, 0.0002:1.00, 0.0004:1.00, 0.0006:1.00, 0.0008:1.00, 0.0010:1.00, 0.0012:1.00, 0.0014:1.00, or 0.0016:1.0 and independently, at least for economy, preferably is not more than, with increasing preference in the order given, 0.010:1.00, 0.0075:1.00, 0.0050:1.00, 0.0040:1.00, 0.0030:1.00, or 0.0025:1.00.

The fluorinated surfactants have the property that they do not substantially reduce the static frictional properties of the surfaces coated according to the invention, so that the undesired “telescoping” of a coil of substrate treated according to the invention is less likely to occur. Silicone polymers are more consistent in preventing blocking but do cause reduced static frictional properties of the surfaces coated with them. A choice between these two types of blocking prevention may be made on this basis.

Optional component (H) of organic solvent may not be needed and when not needed is preferably omitted for economy and avoidance of pollution problems and/or pollution abatement expense. There are at least three reasons, however, why organic solvents may be needed in a composition according to this invention in some instances. First, desired constituents of component (C) may require the presence of organic solvent as an aid in practical preparation of a composition according to the invention. In any such instance, the amount of organic solvent added for this purpose is preferably kept to the minimum required. Secondly, an organic solvent may be useful in removing contaminants from the substrate simultaneously with forming the desired protective coating according to the invention, but ordinarily better results will be achieved if the substrate is conventionally cleaned before any contact with a composition according to this invention. Thirdly and most frequently, component (H) may be needed to avoid cracking of the coating formed in a process according to the invention. Component (H) is unlikely to be needed for this reason if the glass transition temperature of component (C) is not more than 17° C. and is likely to be needed if the glass transition temperature of component (C) is more than 30° C.

When component (H) is included in a composition according to the invention in order to avoid cracking of the coating formed, this component is preferably selected from the group consisting of:

  • esters with a structure that can be made by completely esterifying orthophosphoric acid or sulfuric acid with at least one monoalcohol, which may include halogen atoms and/or ether oxygen atoms in its molecules; and
  • glycols, polyglycols, and the ethers and esters of glycols and polyglycols, i.e., molecules that conform to the general chemical formula (I):
    R1−O—R2−(OR3)n—O—R4 (I),
    wherein:
  • each of R1 and R4, which may be the same or different, represents one of a hydrogen moiety, a monovalent hydrocarbon, halohydrocarbon, or halocarbon moiety, and a monovalent acyl or halo-substituted acyl moiety;
  • each of R2 and R3, which may be the same or different, represents a divalent hydrocarbon, halohydrocarbon, or halocarbon moiety; n represents zero or a positive integer; and
  • the R3 moiety in any one of the n (OR3) moieties may be the same as or different from the R3 moiety in any other distinct one of these (OR3) moieties.
    Preferably, component (H) when present to minimize cracking of the coating is selected from molecules that conform to general formula (I) as given above, and more preferably, independently for each preference stated, the molecules selected conform to general formula (I) when:
  • R1 represents a hydrogen atom and R4 represents an alkyl moiety having a number of carbon atoms that is at least, with increasing preference in the order given, 2, 3, or 4 and independently preferably is not more than, with increasing preference in the order given, 10, 8, 6, 5, or 4;
  • each of R2 and R3 has at least 3 carbon atoms and independently preferably has not more than, with increasing preference in the order given, 10, 8, 6, 5, 4, or 3 carbon atoms;
  • n is not more than, with increasing preference in the order given, 4, 3, 2, or 1.
    Still more preferably, component (H) when present to minimize cracking of coatings formed with it comprises, preferably consists essentially of, or more preferably consists of, two distinct subcomponents as follows:
  • subcomponent (H.1) is selected from molecules that preferably have not more than, with increasing preference in the order given, 9, 8, or 7 carbon atoms each; and
  • subcomponent (H.2) is selected from molecules that have at least 10 carbon atoms each and independently preferably have not more than, with increasing preference in the order given, 15, 14, 13, 12, 11, or 10 carbon atoms each.
    Independently, when both subcomponents (0.1) and (0.2) are present in a composition according to the invention, the mass of (0.1) present has a ratio to the mass of (0.919 2) present that is at least, with increasing preference in the order given, 1.0:1.00, 2.0:1.00, 3.0:1.00, 4.0:1.00, 5.0:1.00, 5.5:1.00, 6.0:1.00, 6.5:1.00, 7.0:1.00, or 7.5:1.00 and independently preferably is not more than, with increasing preference in the order given, 25:1.00, 20:1.00, 18:1.00, 16:1.00, 14:1.00, 12:1.00, 10:1.00, or 8.0:1.00.

Independently of all other preferences, when component (H) is present in a composition according to the invention to minimize crack formation, it preferably has the property that at least, with increasing preference in the order given, 50, 60, 70, 80, 90, 95, or 99% of the amount of component (H) present in a wet coating formed in a process according to the invention is volatilized and therefore not present in the dry coating eventually formed by the process. If the temperature at which a composition according to the invention is to be used is not known, preferably at least, with increasing preference in the order given, 50, 60, 70, 80, 90, 95, or 99% of the amount of component (H) present in a wet layer of a working composition with a thickness of 1.0 millimeter will be volatilized from said wet layer by heating the layer at 121° C. for at least 60 seconds.

Independently of all other preferences, when component (H) is present in a composition according to the invention to minimize cracking of coatings formed with the composition, preferably at least part of it is emulsified into the composition rather than dissolved in it. (The occurrence of emulsification may normally be detected by a cloudy rather than a transparent appearance of the composition when it is mixed.) In order to facilitate the optimal degree of dispersion, preferably at least, with increasing preference in the order given, 50, 60, 65, 70, 75, 80, 85, or 88% of component (H) preferably consists of solvent(s) that have a solubility in water at 25° C. that is not greater than, with increasing preference in the order given, 15, 13, 11, 9.0, 8.0, 7.5, 7.3, 7.1, 6.9, 6.7, or 6.5 grams of solvent per 100 grams of water; and independently at least, with increasing preference in the order given, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, or 11.0% of component (H) preferably consists of solvent(s) that have a solubility in water at 25° C. that is not greater than, with increasing preference in the order given, 7.0, 6.8, 6.5, 6.2, 5.9, 5.6, 5.3, or 5.1 grams of solvent per 100 grams of water.

Also independently of all other preferences, the concentration of component (H) in a working composition according to the invention in which component (H) is present preferably is at least, with increasing preference in the order given, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 4.9% of the total working composition and independently preferably is not more than, with increasing preference in the order given, 30, 25, 20, 15, 10, 9.0, 8.0, 7.0, or 6.0% of the total working composition.

As is generally known in the art, the resistance to leaching of a chromium containing protective coating can be increased by converting part of the initially added hexavalent chromium to trivalent chromium (or, of course, by otherwise supplying trivalent chromium to the composition and correspondingly reducing the content of hexavalent chromium). In general, no trivalent chromium is needed for this purpose in a working composition according to the invention, and if not needed is preferably omitted. In some instances, however, even when no trivalent chromium is desired in the working liquid composition as applied, it is advantageous for some chromium to be converted to a trivalent form during drying of the working composition into place on the substrate surface to be treated. This result may be achieved by using a working composition that contains an organic material that is not readily effective as a reducing agent for hexavalent chromium under the conditions of concentrations and storage and/or use temperature for the working composition, but that is effective as such a reducing agent at higher temperatures, higher concentrations, or both, which are achieved during drying of the liquid coating of working composition. For this purpose, it is preferable to utilize a reducing agent that does not cause any deterioration in the protective quality of the coatings formed. (It is widely believed, although not known with certainty, that the major reaction product from most of these reducing agents is carbon dioxide that escapes as a gas from the liquid composition before the liquid composition dries.) If preferred component (H) selected from molecules conforming to general formula (I) as described above is present, no other material is normally needed for component (I). If only non-reducing solvents or none at all are otherwise present in a composition according to the invention, it is preferred for such a composition to include at least one reducing additive such as at least one of various alcohols, such as by way of non-limiting example glycerol, glycols, such as by way of non-limiting example propylene glycol, sugars, starch, and like organic materials that are suitable for this purpose, as known to those skilled in the art.

When one of these reducing additives is present in a composition according to the invention and all of the chromium present in the composition is supplied to the composition as hexavalent chromium, the mass of the reducing additive present in the composition preferably has a ratio to total mass of chromium present in the same composition that is at least, with increasing preference in the order given, 0.30:1.00, 0.50:1.00, 0.70:1.00, 0.90:1.00, 1.10:1.00, 1.30: 1.00, 1.50:1.00, 1.70:1.00, 1.90:1.00, 2.10:1.00, 2.30:1.00, 2.40:1.00, 2.50:1.00, 2.60:1.00, 2.70:1.00, 2.80:1.00, or 2.86:1.00 and independently preferably is not more than, with increasing preference in the order given, 10:1.0, 8.0:1.0, 6.0:1.0, 5.0:1.0, 4.5:1.0, 4.0:1.0, 3.5:1.0, or 3.0:1.0.

A liquid surface treatment composition according to the invention may be coated onto the substrate by any effective method, such as dipping, spraying, brushing, roll coating, or using an air knife or an electrostatic coating technique, preferably after removing any grease or other soil from the surface of the substrate, to form a liquid coating over the substrate to be treated according to the invention. The coating may be formed on all surfaces of the substrate or on selected portions of the surface only, depending on the positioning of the liquid film from which the dry film is formed.

The passivate compositions of the present invention may be used to treat any type of metal surface but are especially useful for passivating the surface of iron-containing metals such as steel, including zinc-coated and zinc alloy-coated steel such as Galvalume® steel as well as hot dipped galvanized steel.

The passivate composition may be applied to the metal surface using any suitable method such as dipping, rolling, spraying, brushing or the like. The composition is kept in contact with the metal surface for a period of time and at a temperature effective to form the desired corrosion protective coating on the surface. Typically, it will be desirable to apply a wet coating of the passivate composition to the metal surface and then to heat the metal surface to a temperature above room temperature to dry the coating.

A process according to the invention in its simplest form consists of bringing a metal surface to be passivated into physical contact with a working composition according to the invention as described above for a period of time, then discontinuing such contact and drying the surface previously contacted. Preferred metal surfaces include galvanized and/or aluminized steel, and solid alloys of aluminum and/or zinc. Physical contact and subsequent separation can be accomplished by any of the methods well known in the metal treatment art, such as immersion for a certain time, then discontinuing immersion and removing adherent liquid by drainage under the influence of natural gravity or with a squeegee or similar device; spraying to establish the contact, then discontinuing the spraying and removing excess liquid as when contact is by immersion; roll coating of the amount of liquid followed by drying into place, and the like. Drying may be accomplished at ambient temperature, but it is preferred that drying take place at elevated temperatures, with the highest metal temperature (peak metal temperature) achieved not exceeding 250 degrees F. to reduce drying time. Typical processes for use of the invention are roll coating, for galvanized metal surfaces it is preferred that passivation be performed immediately after galvanizing. Roll coating is the preferred method of application in the coil industry where the coil can be galvanized and passivated in a continuous process.

Preferably in roll coating processes, the composition is applied to strips of sheet metal from a coil and is then heated to dry and coalesce the coating. The peak metal temperature reached by the substrate during drying is desirably within the range of 150 to 250 degrees F. The quality of the passivation layer formed is not known to be substantially affected by the temperature during passivating if the temperature is within these preferred limits.

The thickness of the coating is preferably at least 3, 3.5, 4, 4.5, 5, 5.5, 6.0 and is not more than 12, 11, 10 , 9, 8 microns. Preferably, the thickness of the coating formed by the aqueous liquid composition according to the invention corresponds to at least, with increasing preference in the order given, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900 milligrams per square meter of the metal surface passivated (hereinafter usually abbreviated as “mg/m2”), measured as total weight of the coating, and independently, preferably is not more than, with increasing preference in the order given, 1600, 1500, 1200, 1000 mg/m2 measured as total weight of the coating. The desired coating weight varies with the application. The amount of total coating weight added-on may conveniently be measured with commercially available instruments, or by other means known to those skilled in the art.

In certain embodiments, the passivating coating can act as a temporary coating. In this temporary coating embodiment, the passivating coating is intended to provide temporary corrosion protection for preventing corrosion and staining during the time period after galvanizing and prior to final finishing, i.e., during storage and shipping. The passivating coating is then removed and the substrate coated with a more permanent corrosion resistant coating, as is known in the art. For instance, the more permanent corrosion resistant coatings can be provided by a suitable conversion coating process. Suitable conversion coating composition and processes are disclosed in U.S. Pat. Nos. 4,961,794; 4,838,957; 5,073,196; 4,149,909; 5,356,490; 5,281,282; and 5,769,967, which are hereby incorporated by reference. In this embodiment, if the passivating coating is to be removed, it is presently contemplated that this can be readily done by exposing the passivating coating to a suitable alkaline cleaner solution.

Before passivating according to this invention is to be used for any metal substrate, the substrate to be passivated may, but is not necessarily, thoroughly cleaned by any of various methods well known to those skilled in the art to be suitable for the particular substrate to be coated.

Where galvanized metal surfaces are mentioned in connection with the present invention, they are understood to be material surfaces of electrolytically galvanized or hot-dip-galvanized or even alloy-galvanized steel, preferably electrolytically galvanized or hot-dip-galvanized steel strip. By steel is meant unalloyed to low-alloyed steel of the type used, for example, in the form of sheets for automotive bodywork. The use of galvanized steel, particularly electrolytically galvanized steel in strip form, has grown considerably in significance in recent years. The expression “galvanized steel” in the context of the present invention is understood to encompass electrolytically galvanized steel and also hot-dip-galvanized steel and also applies generally to alloy-galvanized steel, zinc/nickel alloys, zinc/iron alloys (Galvaneal) an zinc/aluminum alloys (GALFAN®, from Eastern Alloys, Inc., of Maybrook, N.Y., Galvalume® ™, from BIEC International, Inc. of Vancouver, Wash.) playing a particularly crucial role as zinc alloys.

The practice of this invention may be further appreciated by consideration of the following, non-limiting examples, and the benefits of the invention may be appreciated by the examples set forth below.

EXAMPLES

Examples 1-5

Applicants prepared a series of latexes to assess stability under low pH conditions, which are found in non-chrome thin-film organic passivates.

Example 1 was a cationic latex stabilized by addition of a non-ionic surfactant. This nonionically stabilized cationic latex was prepared a ccording to the following procedure:

TABLE 1
PartIngredientGrams
A)DI water293.5
Triton X-3057.4
B)DI water39.6
Triton X-3059.1
butyl methacrylate40.4
methyl methacrylate39.8
Styrene13.5
2-ethylhexyl acrylate37.1
Hexanediol diacrylate1.2
C)DI water102.9
Triton X-30523.7
butyl methacrylate105.1
Hexanediol diacrylate1.2
2-ethylhexyl acrylate97.5
Styrene35.0
methyl methacrylate104.5
Dimethylaminoethyl methacrylate9.7
D1)70% t-butyl hydroperoxide0.22
DI water2.50
D2)1% Ferrous sulfate0.50
D3)Sodium formaldehyde sulfoxylate0.15
DI water2.50
D4)1% EDTA sodium salt3.1
E)70% t-butyl hydroperoxide2.75
DI water65
F)Sodium formaldehyde sulfoxylate0.65
DI water65
G)DI water22.4
Total1126.0

To a 2 liter four-necked flask, equipped with stirrer, condenser, and nitrogen inlet was added part (A). Stirring and Nitrogen blanket were applied. Parts (B) and (C) were added to and mixed by shaking in separate containers until uniform stable dispersions were obtained. (E) and (F) were added to separate beakers and stirred to form clear solutions. The flask was heated to 40 degrees C. at which time (B) was added followed immediately by addition of (D1) through (D4). The flask contents exothermed to a temperature of 75 C over 30 minutes after which time (C), (E) and (F) were added at a uniform rate over 2 hours. During the two-hour addition, temperature was maintained at 65 degrees C. After additions were complete, (G) was used to rinse (C) residues into the flask. Temperature was maintained at 65 degrees C for a period of 20 minutes at which time the polymerization was complete. The flask contents were cooled and filtered. Final particle size was 173 nm and measured solids were 44.8%.

Example 2 was a cationic latex similar to Example 1, but the amine monomer was not used. This nonionically stabilized cationic latex was prepared according to the following procedure and stabilized by an non-ionic surfactant:

TABLE 2
PartIngredientGrams
A)DI water293.5
Triton X-3057.4
B)DI water142.5
Triton X-30532.9
butyl methacrylate155.2
methyl methacrylate144.3
Styrene48.5
2-ethylhexyl acrylate75.0
Butyl acrylate59.6
Hexanediol diacrylate2.4
C1)70% t-butyl hydroperoxide0.22
DI water2.50
C2)1% Ferrous sulfate0.50
C3)Sodium formaldehyde sulfoxylate0.15
DI water2.50
C4)1% EDTA sodium salt3.1
D)70% t-butyl hydroperoxide2.75
DI water65
E)Sodium formaldehyde sulfoxylate0.65
DI water65
F)DI water22.4
1126.0

To a 2 liter four-necked flask, equipped with stirrer, condenser, and nitrogen inlet was added part (A). Stirring and Nitrogen blanket were applied. Part (B) was added to and mixed by shaking in a container until a uniform stable dispersion was obtained. (D) and (E) were added to separate beakers and stirred to form clear solutions. The flask was heated to 40 degrees C. at which time 180.7 g of (B) was added followed immediately by addition of (C1) through (C4). The flask contents exothermed to a temperature of 75 degrees C. over 30 minutes after which time the remainder of (B), (D) and (E) were added at a uniform rate over 2 hours. During the two hour addition, temperature was maintained at 65 degrees C. After additions were complete, (F) was used to rinse (B) residues into the flask. Temperature was maintained at 65 degrees C. for a period of 20 minutes at which time the polymerization was complete. The flask contents were cooled and filtered. Final particle size was 148 nm and measured solids were 45.6%.

Example 3 and 4 were cationic latexes stabilized by the incorporation of a polymerizable non-ionic surfactant into the polymer chain and were prepared as follows:

TABLE 3
PartIngredientGrams
ADI water146.8
Noigen RN-202.6
B)DI water71.3
Noigen RN-2011.5
butyl methacrylate77.6
methyl methacrylate72.2
Styrene24.3
2-ethylhexyl acrylate67.3
Hexanediol diacrylate1.2
C1)70% t-butyl hydroperoxide0.11
DI water1.3
C2)1% Ferrous sulfate0.25
C3)Sodium formaldehyde sulfoxylate0.08
DI water1.3
C4)1% EDTA sodium salt1.6
D)70% t-butyl hydroperoxide1.4
DI water33
E)Sodium formaldehyde sulfoxylate0.33
DI water33
F)DI water11.2
558.4

To a 2 liter four-necked flask, equipped with stirrer, condenser, and nitrogen inlet was added part (A). Stirring and Nitrogen blanket were applied. Part (B) was added to and mixed by shaking in a container until a uniform stable dispersion was obtained. (D) and (E) were added to separate beakers and stirred to form clear solutions. The flask was heated to 40 degrees C. at which time 90.3 g of (B) was added followed immediately by addition of (C1) through (C4). The flask contents was heated to a temperature of 65C over 30 minutes after which time the remainder of (B), (D) and (E) were added at a uniform rate over 2 hours. During the two hour addition, temperature was maintained at 65 degrees C. After additions were complete, (F) was used to rinse (B) residues into the flask. Temperature was maintained at 65 degrees C. for a period of 20 minutes at which time the polymerization was complete. The flask contents were cooled and filtered. Final particle size was 268 nm and measured solids were 45.5%.

Example 4 is an additional non-ionically stabilized latex prepared using the formulation and procedure described by example 3. Final particle size was 217 nm and measured solids were 45.1%.

Example 5 is a Comparative Example using a cationic latex typical of those used in the coil industry stabilized by use of a polymerizable anionic surfactant. This cationic latex was prepared according to the following procedure, and was stabilized by the incorporation of the anionic stabilizing groups into the polymer chain of the resin:

TABLE 4
PartIngredientGrams
A)DI water293.6
B)butyl methacrylate64.0
methyl methacrylate59.5
Styrene20.0
butyl acrylate55.5
Hexanediol diacrylate1.0
Hitenol BC-106.0
C)Ammonium persulfate0.4
DI water5.0
D)DI water105
Total610.0

To a 2 liter four-necked flask, equipped with stirrer, condenser, and nitrogen inlet was added part (A). Stirring and Nitrogen blanket were applied. Part (B) was added to and mixed by stirring in a separate container. (C) was added to a beaker and stirred to form clear solution. The flask was heated to 80 degrees C. after which time 41.2 g of (B) was added followed by addition of (C). The flask contents were maintained at a temperature of 80 C while the remainder of (B) was added over 3 hours. After additions were complete, (D) was added to the flask. Temperature was maintained at 80 degrees C. for a period of 30 minutes at which time the polymerization was complete. The flask contents were cooled and filtered. Final particle size was 95 nm and measured solids were 33.4%.

Triton X-305 is a nonionic surfactant from Dow Chemical. EDTA is ethylenediaminetetraacetic acid. Noigen RN-20 is a polymerizable nonionic surfactant from DKS International, Inc. Hitenol BC-10 is a polymerizable anionic surfactant from DKS International, Inc.

Examples 6-18

Commercially available resins, as well as those of Examples 1-5, were utilized to make non-chrome, thin-film organic passivate compositions, according to Tables 5 and 6, below. In Examples 6-12, the ratio of Part A to Part B was 1:1 parts by volume. When the resin of Example 5 was mixed with the other constituents, the composition gelled and no further testing of Example 5 was done.

TABLE 5
COMPONENT A
(grams)COMPONENT B (grams)
%H2OH3PO4H2TiF6H2ODequestHA
EXSolidsDI75%50%DI201016LubeAPP*Ex 1Ex 2Ex 3Ex 4
615.8689.573.546.21235.36.5
716.3689.573.536.21235.36.510
824.7989.573.56.512756.5
924.7289.573.56.5126.575
1024.7989.573.56.5126.575
1124.9889.573.56.5126.575
1224.8189.573.56.5126.575

*Amino-phenolic polymer

Non-chrome, thin-film organic passivate compositions were made as two pack compositions by first formulating Component A and Component B as found in Table 5, and then combining the two components. The passivate compositions were also formulated as one pack compositions, as found in Table 6, below, by combining all constituents of the composition in a single batch mix, rather than formulating separate components.

TABLE 6
H2OH3PO4H2TiF6DequestHA
EXDI75%50%Bonderite NT-12010LubeEx 1Ex 216
1344.753.51.7566.537.5
1445.453.51.7566.536.8
1545.453.51.7566.536.8
1638.753.51.75666.537.5
1739.453.51.75666.536.8
1839.453.51.75666.536.8

Amounts are in grams

The pH of Examples 6-18 was 2.6. Bonderite NT-1 is a phosphate free surface treatment containing inorganic oxide particles and dissolved fluorometallate anions commercially available from Henkel Corporation. Dequest 2010 is an aqueous solution of phosphonic acids comprising approximately 60 wt % 1-hydroxyethylidene-1, 1-diphosphonic acid commercially available from Solutia, Inc. The lubricant used for Examples 6-18 was ML160, a waterborne wax emulsion commercially available from Michelman, Inc.; it is described in product literature as a low VOC, anionic carnauba wax having a particle size of 0.135 microns, a melting point of 85° C. and an ASTM D-5 hardness of 1. HA16 in Tables 5 and 6 is Rhoplex HA-16, commercially available from Rohm & Haas it is described in product literature as a nonionic, self cross-linking acrylic emulsion polymer having a pH of 2.6 and a solids wt % of 45.5.

Variations of the compositions of Examples 13-18 were also prepared. For Examples 13C, 14C and 15B, the formulations in Table 6 were made according to Examples 13,14 and 15, respectively, with the exception that additional distilled water was used in place of the Dequest 2010 to achieve 100 grams total weight. The remaining variations of Examples 13-18 were made according to their respective Examples 13-18, and additional components were introduced, as recited in the Additives column of Table 7. The pH of Examples 6-18 was 2.6, including the variations was 2.6.

The compositions were tested for phase stability, based on phase separation or coagulation after mixing that was visible to the unaided human eye, and storage stability, which was assessed by aging the composition at 100° F. for 6 months and observing whether phase separation or coagulation, visible to the unaided human eye, had taken place.

TABLE 7
Stability Testing
Storage
Stability
FormulationResinAdditivesPhase Stability@ 100° F.
Example 6Rhoplex HA16passfail
Example 7Rhoplex HA16passfail
Example 8Rhoplex HA16passfail
Example 9Example 1passPass
Example 10Example 2passPass
Example 11Example 3passPass
Example 12Example 4passPass
Example 13AExample 1passPass
Example 13BExample 10.02% Byk 348passPass
Example 13CExample 1w/o Dequest 2010passPass
Example 13DExample 11% Nyacol DP 5370passPass
Example 14AExample 2passPass
Example 14BExample 20.02% Byk 348passPass
Example 14CExample 2w/o Dequest 2010passPass
Example 14DExample 21% Nyacol DP 5370passPass
Example 15ARHOPLEX HA 16passfail
Example 15BRHOPLEX HA 16w/o Dequest 2010passfail
Example 16AExample 1passPass
Example 16BExample 11% Nyacol DP 5370passPass
Example 17AExample 2passPass
Example 17BExample 21% Nyacol DP 5370passPass
Example 18ARHOPLEX HA 16failFail
Example 18BRHOPLEX HA 161% Nyacol DP 5370failFail

Byk 348 is a wetting agent, commercially available from Byk Chemie. Byk 348 is a silicon surfactant, based on the polyether modified poly-dimethyl-siloxane. Nyacol DP 5370 is a commercially available aqueous dispersion of nanoparticulate zinc oxide.

Examples 19-28

Non-chrome, thin-film organic passivate compositions containing vanadium were formulated according to Table 8, below.

TABLE 8
Non-chrome thin film passivate formulations containing Vanadium
pbwEx. 19Ex. 20Ex. 21Ex. 22Ex. 23Ex. 24Ex. 25Ex. 26Ex. 27Ex. 28
DI Water36.636.342.2540.9540.9543.3539.6557.1559.7557.15
V2O5111111
NH4VO31.31.31.31.3
50% NaOH2.32.32.32.32.32.32.3
45% KOH3.6
28% NH4OH3.6
LiOH•H2O1.2
Dequest6666666666
2010
75% H3PO45.45.45.45.45.45.4775.47
50% H2TiF61.751.751.751.751.751.751.751.751.751.75
Nyacol1
BP 5370
Zinc Oxide11
Permax 22023.623.6
Permax 20018.7518.75
Resin 117.517.517.517.517.5171717
Resin 217.317.317.317.317.3
Lube6.56.56.56.56.56.56.56.56.56.5

Permax 220 and 200 are nonionically stabilized urethane resins available from Noveon Inc. and described as aliphatic polyether waterborne urethane polymers constituting about 35-44% solids. Resin 1 and 2 are nonionically stabilized acrylic resins with a solids content of approximately 45-50%. The lubricant used for Examples 19-28 was ML160, a waterborne wax emulsion commercially available from Michelman, Inc.

Galvalume® and Hot Dip Galvanized (HDP) steel panels were obtained from the National Steel, Trenton, Mich. The panels were coated with the compositions as recited in Table 8 using a #3 drawbar and also with a laboratory scale roll coater designed to approximate industrial roll coating conditions. All panels were dried in an oven and reached a peak metal temperature (PMT) of 200° F.

TABLE 9
Corrosion results
Ex. 19Ex. 20Ex. 21Ex. 22Ex. 23Ex. 24Ex. 25Ex. 26
%%%%%%%%
Corrosion/Corrosion/Corrosion/Corrosion/Corrosion/Corrosion/Corrosion/Corrosion/
HrsHrsHrsHrsHrsHrsHrsHrs
Neutral Salt5-6485-9365-10081-10082-10082-10083-10082-600
Spray on
Galvalume ®
Neutral Salt7-3127-4325-4203-16810-33610-16810-3363-264
Spray on
HDG
Stack Test10-16830-1685-100810-10083-100810-84010-8403-1008
on
Galvalume ®
Stack test7-33610-16810-50410-5043-5047-5047-33610-672
on Hot
Dipped
Galvanized
Butler10-201610-18483-20165-100810-6723-10080-10080-1008
Water
Immersion
test on
Galvalume ®
Butler3-1687-1685-5043-33610-100810-10087-3367-336
Water
Immersion
test on
HDG
Cleveland10-672100-3607-10083-10083-10083-10083-6723-672
Condensing
on
Galvalume ®
Cleveland10-67240-3607-100810-100810-10083-100810-6725-672
Condensing
on Hot
Dipped
Galvanized

Example 29

Formula Part (A), which was the same as the Control, was a mixture of the substances recited in Table 10, added sequentially with low speed agitation until uniform in consistency:

TABLE 10
Parts per
Constituenthundred parts by weight
Acrylic emulsion resin45.6
De-ionized water39.1
Wax emulsion8.7
Ammonium dichromate (10% wt) intermediate6.4
Silicone anti-block0.2

Formula Part (B) was a commercially available conventional sized or nanoparticulate dispersion of metal and/or metalloid oxide powder. A number of the dispersions include a stabilizer in small amounts to aid in sustaining uniform dispersion of the particles.

The candidate compositions were prepared by combining Part A and Part B using one of the following alternative methods to produce the particular Formula to be tested, as follows:

    • I. Direct addition using low-speed agitation of Part (B) to Part (A) in relative amounts pre-calculated to achieve the targeted pigment volume concentration, with subsequent maintenance of low-speed agitation until uniform in consistency (Formulas 1, 2A-C, 3A-C, 4, 5, 6, & 12);
    • II. Method I. modified by the application of extended high-speed dispersion of initially mixed Parts (A) and (B) until uniform in consistency (Formulas 7A-C, 8, & 9);
    • III. Pre-neutralization of Part (B) to pH˜8.0, followed by processing according to Method I. (Formulas 10A-D & 11A-D).

The composition of Formulas 1-12 is recited in Table 11.

TABLE 11
Mean
Pigmentdiameter,Dry film% Pigment Volume Concentration (PVC)
typenmStabilizerappearance*5%10%15%20%30%40%50%
SiO215ammoniaInitial light amber1
fading to colorless,
transparent,
high gloss
SiO215noneInitial light amber 2A 2B 2C
fading to colorless,
transparent,
high gloss
TiO2250AluminaInitial light amber 3A 3B 3C
zirconiafading to colorless,
sl.-mod. opaque,
high gloss
TiO2250AluminaInitial light amber4
silicafading to colorless,
sl.-mod. opaque,
high gloss
TiO225proprietaryInitial green-gray5
organicfading to colorless,
mod. opaque, high
gloss
ZnO100noneInitial light yellow-6
green fading to
colorless,
transparent, high
gloss
ZrO25-10acetic acidInitial light yellow- 7A 7B 7C
green fading to
colorless,
transparent, high
gloss
ZrO25-10nitric acidInitial light yellow-8
green fading to
colorless,
transparent, high
gloss
ZrO2100Nitric acidInitial light yellow-9
green fading to
colorless, sl.
opaque, low gloss
Sb2O55TEAInitial green-gray10A10B10C10D
phosphatefading to colorless,
transparent, high
gloss
Sb2O535TEAInitial green-gray11A11B11C11D
fading to colorless,
transparent, high
gloss
CeO220proprietaryPersistent medium12 
organicamber, sl.-mod.
opaque, low
gloss

The Formulas prepared according to Table 11 were tested for their effect upon the emittance of a typical metal roofing material. For each Formula, a series of Fairfield Galvalume® panels was coated at different coating weights using a draw down bar.

The progressive dissipation of initial color noted in panels produced from all mixtures except Formula 12 was observed to be dependent wholly or mostly on extended light, rather than heat, exposure. In general, the progression from the initial residual colored appearance to colorless was complete within about 24-48 hours under conditions of ambient indoor illumination.

The coated panels were evaluated for emittance and reflectence of EMR as described in Table 12. Formula Part A was used as the control.

TABLE 12
Mean
PigmentDiameter,CoatingSolar
Formula IDtypenmStabilizationwt, mg/ft2*Emittance**Reflectance†
ControlnoneN/AN/A 00.060.78
1170.220.69
1290.34
2530.37
3100.36
3160.39
3690.410.64
3850.42
4100.38
 1SiO215Ammonia2280.39
3000.45
3920.48
 2ASiO215None6560.65
 2BSiO215None6880.66
 2CSiO215None7120.67
 3ATiO2250alumina/zirconia2340.37
4390.50
 3BTiO2250alumina/zirconia2670.42
4550.58
 3CTiO2250alumina/zirconia2960.55
5300.66
 4TiO2250alumina/silica2720.37
4260.53
 5TiO225proprietary1680.44
organic2890.53
4110.61
 6ZnO100none1740.24
3110.37
4080.45
 7AZrO25-10acetic acid2120.41
3130.52
4070.580.64
4880.60
6230.62
6710.69
7210.71
8030.71
8960.72
9310.72
1053 0.740.62
 7BZrO25-10acetic acid5170.670.64
5470.69
5600.70
6330.740.62
 7CZrO25-10acetic acid4760.67
5050.70
5000.71
5420.72
5760.740.62
 8ZrO25-10nitric acid2690.57
2980.64
4200.71
5020.74
5880.750.62
5690.78
 9ZrO2100Nitric acid4030.61
10ASb2O55TEA phosphate3260.49
4640.53
5490.57
6990.61
8280.65
9860.67
1091 0.70
10BSb2O55TEA phosphate3350.55
4850.61
6060.66
6710.68
10CSb2O55TEA phosphate3410.59
5250.66
6040.68
6280.70
10DSb2O55TEA phosphate3010.57
3230.61
4410.65
4820.69
5490.71
6420.73
11ASb2O535TEA6240.59
11BSb2O535TEA3200.59
4240.63
5030.67
5390.67
6200.71
6590.73
7030.750.60
11CSb2O535TEA4080.62
3380.62
4760.69
4800.70
4920.70
5740.74
6640.77
11DSb2O535TEA3860.63
4160.66
4600.69
5280.73
5420.76
5930.77
5160.78
12CeO220proprietary8860.50
organic1244‡ 0.57
1461‡ 0.62

*Coating weight calculated from XRF Cr analysis and known Cr composition of mixture, assuming quantitative loss of volatiles.

**Emittance measured per ASTM C1371-04a using a Devices and Services Model AE/RD1 Emissometer.

Solar Reflectance measured per ASTM C1549 using a Devices and Services Model SSR-E Solar Spectrum Reflectometer with Air Mass 2 spectral weighting.

Coating weight skewed high due to spectral interference between Cr and Ce at the analytical wavelength.

A series of Fairfield Galvalume® panels was coated at the below coating weights using a draw down bar.

ControlFormula 7A
Cr cwt, mg/ft2 applied:1.610.7
Total cwt, mg/ft2 applied:1201050

TABLE 13
ASTM D610
Corrosion Rating
Test ProcedureDurationControlFormula 7A
Neutral Salt Spray*1000 hrs910
Cleveland condensing humidity1000 hrs910
Butler water immersion1000 hrs610
Stack2000 hrs78

*Rating on roll-formed panels. Rating is exclusive of performance along the length of convex ridges of the roll-formed profile, where localized corrosion occurred due to film fracture during forming.

Although Formula 7A was not optimized for corrosion resistance at the lowest possible chromate concentration, the corrosion resistance was at least as good as the control at the coating weight that provided emittance of 0.74.

Although the invention has been described with particular reference to specific examples, it is understood that modifications are contemplated. Variations and additional embodiments of the invention described herein will be apparent to those skilled in the art without departing from the scope of the invention as defined in the claims to follow. The scope of the invention is limited only by the breadth of the appended claims.