Title:
Anticorrosive paint
United States Patent 2038444


Abstract:
This invention relates to anti-corrosive paints. The applicant has discovered that especially effective anti-corrosive paints can be produced if there are used as pigments lead salts, the anions of which have an anti-corrosive action, owing to the formation of a passive protecting layer on...



Inventors:
Manfred, Ragg Alphonse Friedric
Application Number:
US60694932A
Publication Date:
04/21/1936
Filing Date:
04/22/1932
Assignee:
Manfred, Ragg Alphonse Friedric
Primary Class:
Other Classes:
106/256, 106/257, 252/387, 423/594.9
International Classes:
C09D5/08
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Description:

This invention relates to anti-corrosive paints.

The applicant has discovered that especially effective anti-corrosive paints can be produced if there are used as pigments lead salts, the anions of which have an anti-corrosive action, owing to the formation of a passive protecting layer on the surface of the iron and among these lead salts the most useful have been found to be those that contain acids of the main series of the 5th group of the periodic system-i. e., the acids of P, N, Sb, As and Bi.

The two last-mentioned elements may be omitted on account of poisonous nature or expense, so that actually only the lead salts of the i5 phosphoric acids, nitric acid, nitrophosphoric acids and antimonic acids come into question for practical use.

The lead salts selected are those which preferably possess, in addition to the above mentioned property of rendering the coating passive, other valuable painting properties, especially a good hiding capacity and a suitable tint, and those salts which can be produced from cheap raw material and these requirements are best met by the basic lead salts of the antimonic acids, which possess a pleasing grey tint with a good hiding capacity.

If lead salts are used which do not possess inherent hiding capacity, e. g., the nitrates, phosphates or nitrophosphates, they must be used along with other covering pigments, such as titanium white, white lead, basic lead antimonate, zinc oxide and the like.

To produce a good anti-corrosive paint in accordance with the invention it is only necessary to grind one of the aforesaid salts, or a mixture thereof, in the known manner, with a suitable binding agent such as boiled linseed oil, Stand oil or China wood oil.

For example, 52 parts of lead phosphate and (in order to increase the hiding capacity) 20 parts of white lead or zinc oxide are ground in a hopper mill or on a rolling mill with 25 parts of China wood oil or Stand oil, 1 part of a drier and 2 parts of white spirit, or 72 parts of basic lead antimonate, are ground as above with 25 parts of China wood oil or Stand oil, 1 part of a drier and 2 parts of white spirit.

The invention is not limited to any special method of producing the salts mentioned, but a process will be described for producing basic lead salts of antimonic acids which are particularly suitable as pigments.

This process consists in (a) Heating lead oxide or oxidic lead compounds with metallic antimony which react as follows:16PbO+4Sb+502=2[5PbPbO.Pb3(Sb4)2] or 16PbO+4Sb+502=2[7PbO.Pb(Sb03) 2 (b) Heating oxidic antimony compounds with PbO or Pb, which react as follows:2Sb203-+ 16PbO+202=2 [5PbO.Pb3 (Sb04) 2] or 2Sb204+16Pb+ 902=2 5PbO.Pb3(SbO4) 2] or (c) Oxidizing metallic antimony and metallic lead conjointly and then causing the oxides to interact as above, the reaction being as follows:2Sb2+16Pb+1302=2[5PbO.Pb(SbO4) 2] The following examples are given for carrying the invention into practice:Example I.-Very finely powdered litharge is intimately mixed with antimony powder in ac- 20 coidance with the stoichiomctric ratio, i. e., about 890 parts of PbO with 120 parts of Sb and heated in a known device, e. g., a rotating drum, with admission of air to 350-400° C. The final product is basic lead antimonate of a grey colour, 25 which, ground as aforesaid with a suitable binding agent, can be used alone or with other pigments as an anti-corrosive plaint. Instead of lead oxide, other oxidic lead compounds, e. g., white lead, may be used. The proportions stated 30 may be varied within certain limits. In this way, light grey pigments, for example, can be produced which have the composition 3PbO.Pb3(Sb04)2. This product is therefore less basic than the preceding one. 35 Example II.-60.8 kgs of antimony tetroxide are thoroughly mixed with 345.6 kgs. of very finely powdered lead and heated gradually in a heatable rotating drum or other suitable apparatus with 40 powerful admission of air to 350-400° C. The grey final product has the same composition as in Example I. Instead of antimony tetroxide antimony sulphide (Sb2S3) may be used, which when heated in the presence of air is converted 45 into antimony oxides.

Example III.-If it is preferred to start directly with the metals, they may be melted together in accordance with the formula 3PbO-Pb3(Sb04)2, i. e. approximately in the proportion of 240 Sb 50 to 1296 Pb, and then, in a very finely atomized condition, subjected to the action of atmospheric oxygen. The Pb and the Sb are thus rapidly converted into oxides which, in the nascent state, combine to form a finely-powdered grey basic 55 lead antimonate of the above composition which does not contain any free PbO.

The process can be carried out in any desired apparatus. So for instance in the apparatus as shown in the accompanying drawing.

In this drawing there is rotatably mounted within a preferably cylindrical casing a a stepped horizontal disk or dish b on a vertical shaft c. The disk or dish b is provided with a central cup c from which radial furrows e branch off. The cup d as well as the furrows e may be let into the disk b or may be produced by cutting into the latter.

The casing a is provided with a cover / on which rest feet g of a vessel h adapted to be filled with molten metal or in which metal may be melted by the aid of a gas burner i. The bottom of the vessel h has a central outlet which may be closed by a valve k and from which projects downwardly a pipe n terminating just above the cup d in th centre of the disc b. The flow of the molten liquid is regulated by the valve k, the spindle of which is screwed into the cover or top of the vessel h and is provided at its upper end with means for rotating the valve spindle, for instance a crank m, to regulate the valve, so as to allow the metal to flow into the cup d, either in a fine jet or in drops.

Below the rim of the disk b is an annular channel r into which projects or project one or more scrapers s attached to the disk b, whereby to convey any material that has been gathered in the channel r to the outlet t. Means, for instance a gas burner u, is provided to heat the disk b.

From the top / of the casing a thermometer v may be suspended so that the temperature within the casing or above the disk may be read off from outside. Another pipe w may be provided for allowing air to be fed into the casing.

In the operation of the apparatus the molten metal is atomized on the rapidly rotating heated dish b in the presence of air which supplies the oxygen that is necessary for the reaction. The individual particles of the molten metal become coated with a grey envelope of basic antimonate, whilst, owing to the high velocity with which the particles fly through the reaction chamber, the core still consists of unchanged metal. The combination of metallic pigments with basic antimonates is advantageous, for electrochemical reasons, for the production on the iron of the protecting coating layer mentioned at the commencement hereof. In the apparatus described, pigments containing the basic antimonates can be produced rapidly and continuously.

I claim:1. An anti-corrosive paint comprising a pigment which consists essentially of basic lead antimonate, a vehicle and a drier, said basic lead antimonate being present in a quantity sufficient to form a passive protecting film upon the surface of the object coated.

2. An anti-corrosive paint comprising a pigment which consists essentially of a basic lead salt of the antimonic acids, a vehicle, and a drier, said basic lead salt being present in a quantity sufficient to form a passive protecting film upon the surface of the object coated.

3. Anti-corrosive paints, the pigments of which cdnsist of basic lead salts of antimonic acids enveloping a metallic core, said pigments being present in a quantity sufficient to form a passive protecting film upon .the surface of the object coated.

4. An anti-corrosive paint, the-pigment of which consists essentially of insoluble basic lead salts of the oxygen acids of the elements of the 5th main group of the periodic system, said pigment being present in a quantity sufficient to form a passive protecting film upon the surface of the object coated.

5. An anti-corrosive paint the pigment of which consists of the basic lead salts of acids of phosphorus containing oxygen, said pigment being present in a quantity sufficient to form a passive protecting film upon the surface of the object coated.

6. An anti-corrosive paint comprising basic lead phosphate, white lead, a vehicle and a drier, said basic lead phosphate being present in a quantity sufficient to form a passive protecting film upon the surface of the objectcoated.

ALPHONSE FRIEDRICH MANFRED RAGG.