05/425827

09/16/1975

12/18/1973

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The Furukawa Electric Co., Ltd. (Tokyo, JA)

252/79.400

134/27, 134/41, 134/3, 216/108, 252/79.100

C23F1/16; C23G1/02; C23F1/10; C23F3/04; C23F3/02

156/18,20 252/79.1,79.4,316 134/3,27,41

3598741		August 1971	Kanno
3801512		April 1974	Solenberger

Van Horn, Charles E.

Massie, Jerome W.

Wenderoth, Lind & Ponack

What is claimed is

1. A solution for the chemical dissolution treatment of metal materials comprising water, 0.1 to 10 g/l in hydrogen-ion concentration of an acid, 0.1 - 300 g/l of hydrogen peroxide and 0.001 - 20 g/l of at least one compound selected from the group consisting of

2. A solution according to claim 1, in which the concentration of the alcohol polyoxyethylene ether is 0.1 to 15 g/l.

3. A solution according to claim 1, in which the concentration of the alkyl hydrogen phosphate, the alkyl hydrogen phosphite or their salts is 0.01 to 5 g/l.

4. A solution according to claim 1, in which R₁ of the alcohol polyoxyethylene ether is an aliphatic hydrocarbon residue having 8 to 18 carbon atoms.

5. A solution according to claim 1, in which R₁ of the alcohol polyoxyethylene ether is an aliphatic hydrocarbon residue having 12 to 16 carbon atoms, and n is 6 to 12.

6. A solution according to claim 1, in which R₃ and R₄ are normal chain alkyl groups, each having 2 to 8 carbon atoms.

7. A solution used for the pickling of metal materials according to claim 1, in which the concentration of the hydrogen peroxide is 0.1 to 100 g/l.

8. A solution used for the etching or chemical milling of metal materials according to claim 1, in which the concentration of the hydrogen peroxide is 5 to 200 g/l.

9. A solution used for the chemical polishing of metal materials according to claim 1, in which the concentration of the hydrogen peroxide is 10 to 300 g/l.

10. A solution according to claim 1, in which the acid is sulfuric acid, sulfamic acid, acetic acid, hydrochloric acid, phosphoric acid, hydrofluoric acid, fluoroboric acid, or hydrofluosilicic acid.

11. A solution for the chemical dissolution treatment of metal materials according to claim 1, in which the acid is sulfuric acid.

12. A solution for the chemical dissolution treatment of metal materials according to claim 1, in which the solution contains at least hydrofluoric acid as the acid.

13. A solution for the chemical dissolution treatment of metal material according to claim 1, which further contains 0.1 to 5,000 ppm of glue, gelatine or hydrolyzates thereof.

14. A solution for the chemical dissolution treatment of metal materials according to claim 1, which further contains 1 to 500 ppm of glue, gelatine or hydrolyzates thereof.

15. A solution according to claim 1, containing the alcohol polyoxyethylene ether.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to solutions used for dissolution treatment of metallic materials, more particularly, to solutions which comprise acid solutions containing hydrogen peroxide and a small amount of such organic compounds that no only inhibit decomposition of hydrogen peroxide but also exhibit useful functions profitable to the chemical treatment.

The term "chemical dissolution treatment" used herein refers to the treatments in general for chemically dissolving metals or metallic compounds such as oxide scale adhering to the surface of the metals, including from the technical standpoint, pickling, etching, chemical milling and chemical polishing. Pickling is a process in which oxide scales produced in high temperature processing of metallic materials or during their storage are removed. Etching and chemical milling are processes to give a desired shape to a metallic material by dissolving unnecessary parts of the material. Chemical polishing is a treatment to produce a smooth and bright surface on metallic materials by dissolving the surface layer under a specified condition.

2. Description of the Prior Art:

So far, a variety of aqueous solutions were used for these treatments, employing as major constituents strong acids such as sulfuric and hydrochloric acids and oxidizing agents such as chromic acid and nitric acid. Special metals such as titanium, niobium and stainless steel require use of hydrofluoric acid in solutions for their chemical dissolution treatment, but those acids which are relatively harmless in the environmental pollution such as sulfuric, sulfamic and hydrochloric acids may be used for ordinary metals. On the other hand, there exists a difficulty with the oxidizing agent. Chromic acid produces hexavalent chromium ions and nitric acid produces nitrogen oxide gas, both being harmful. Therefore, the processes employing these oxidizing agents require a large scale plant and a high cost to prevent pollution and to maintain good working environment. These processes are not desired because of the economical drawbacks in economy and environmental policy. Problems arise with copper and alloys thereof which have ionization tendency lower than that of hydrogen, since these metals need an oxidizing agent to dissolve in an acid. The same problem concerning harmful materials from oxidizing agents is common when hydrofluoric acid is used as acid.

To overcome the difficulty, an attempt has been made to employ hydrogen peroxide as oxidizing agent. For example, an aqueous solution containing 0.1 to 300 g/l of hydrogen peroxide and 0.1 to 10 g/l in hydrogen-ion concentration of acid components (hereinafter the solution will be designated as hydrogen peroxide acid solution) was used. But the solution proved to have difficulties in the technical sense as specified in the following:

1. Hydrogen peroxide is decomposed catalytically by the action of metallic ions dissolved in the solution. This means not only economical loss but also difficulty of stable treatment in uniformly dissolving metallic materials in the technical scale. Hydrogen peroxide is known to be unstable in itself and to be acceleratingly decomposed by the catalytic action of heavy or noble metals. For instance, in an aqueous solution containing 10 g/l of hydrogen peroxide and 100 g/l of sulfuric acid at 60°C the rate of decomposition of hydrogen peroxide in the presence of 0.5 g-mole/l of various metal ions is as follows:

Table 1 ______________________________________ Metal ion Rate of Decomposition (g-H ₂ O ₂ /l min.) Fe ^{+ + +} >3 Cu ^{+ +} 1.7 × 10 ^{- 1} Mn ^{+ +} 3.8 × 10 ^{- 2} Cr ^{+ + +} 2.2 × 10 ^{- 2} Ni ^{+ +} 5.0 × 10 ^{- 3} Zr ^{+ +} 4.2 × 10 ^{- 3} None 3.3 × 10 ^{- 3} ______________________________________

2. Hydrogen peroxide is decomposed on the surface of heavy metals by contact catalysis. Even if the above decomposition could be prevented, mist of acid will inevitably be generated, which will result in deterioration of working conditions.

3. Generally lustrous finished surfaces are required in the chemical dissolution treatment of metallic materials. But the treatment with the hydrogen peroxide acid solution gives a non-lustous surface. Further even when the treatment solution is contaminated with chloride ions having such a low concentration as encountered in city water, the rate of dissolution is decreased by several tens of percents.

4. If brass materials in the form of tubes, wires, bars, plates and strips are treated in a bundle, red strains appear at the contact area on the materials.

As a countermeasure to the first probelm (1), U.S. Pat. No. 2,154,455 describes use of lower alcohols, sodium pyrophosphate, sodium stannate and glycerine as a stabilizing agent for hydrogen peroxide. Further, carboxylic acids and chelating agents (such as amino-carboxylic acids and 8-oxyquinoline) are suggested to be useful as stabilizing agents for hydrogen peroxide. However, these substances are rather poor in their ability as stabilizing agent and they should be applied in a fairly high concentration which is not acceptable in most cases. Glycerine and some alcohols cause a decrease in the rate of dissolution of metals. Lower alcohols and carboxylic acids that are volatile produce bad smell. Sodium stannate may often become colloidal and sticks to and stains materials under treatment. Pyrophosphoric acid is apt to be hydrolyzed in an acid solution. Chelating agents have to be used in a large excess over the amount of metal ions dissolved, and only poor effect could be expected.

U.S. Pat. No. 3,293,093 describes, as a countermeasure to the third problem (3), addition of mercury salts, silver salts, phenacetine and sulfathiazole, the additives all being toxic and expensive. Salts of mercury and silver have only limited application because they may deposit on the materials being treated.

The second and fourth problems described above remain still unsolved.

SUMMARY OF THE INVENTION

The object of the present invention is to provide solutions for chemical dissolution treatment of metallic materials which can be applied to metallic materials constantly and uniformly for a sufficiently long period, suppressing wasteful decomposition of hydrogen peroxide, by adding a small amount of stabilizing agent.

Further object of this invention is to provide solutions for chemical dissolution treatment of metallic materials with which, even when the treatment solutions are contaminated by chloride ions, lustrous finished surfaces of metallic materials could be produced without decreasing the rate of dissolution of metals.

Still further object of this invention is to provide solutions for dissolution treatment of metallic materials which do not produce mist of acid on dissolving metallic materials.

Another object of this invention is to provide solutions for chemical dissolution treatment of metallic materials with which red strains, that are otherwise likely to form on brass materials, could be prevented from forming.

According to the present invention there is provided a solution for the chemical dissolution treatment of metallic materials comprising a mixed aqueous solution of 0.1 to 10 g/l in hydrogen-ion concentration of an acid, 0.1 to 300 g/l of hydrogen peroxide, and 0.001 to 20 g/l of at least one compound to prevent the decomposition of the hydrogen peroxide selected from the group consisting of;

a. an alcohol polyoxyethylene ether represented by the formula

R ₁ O(C ₂ H ₄ O) _n H,

b. an alkylsulfonic acid represented by the formula

X--R ₂ --SO ₃ H or its salts,

c. an alkyl hydrogen phosphate represented by the formula ##SPC1##

d. an alkyl hydrogen phosphite represented by the formula ##SPC2##

e. an alkyl hydrogen sulfate represented by the formula

R ₃ OSO ₃ H or its salts

wherein R ₁ is an aliphatic hydrocarbon residue having 4 to 20 carbon atoms n is an integer of 2 to 20, R ₂ is an alkyl group having 1 to 18 carbon atoms X is hydrogen or sulfonic group, R ₃ is an alkyl group or hydroxyalkyl group, each having 1 to 12 carbon atoms and R ₄ is hydrogen, or an alkyl group or hydroxyalkyl group, each having 1 to 12 carbon atoms.

DETAILED DESCRIPTION OF THE INVENTION:

The solution for the chemical dissolution treatment of metallic materials of the present invention will be explained with respect to its components.

The concentration of the first component, hydrogen peroxide, is 0.1 to 300 g/l, preferably 1 to 200 g/l. The accelerated dissolution of metals cannot be practically expected at a concentration below 0.1 g/l, while for a high concentration exceeding 300 g/l metals are dissolved too vigorously, or sometimes the oxide of the metal is not dissolved, depending on the redox potential of the system. Therefore the range of concentration referred to above should be maintained. Within the range of concentration, however, metals are dissolved more quickly at a higher concentration of hydrogen peroxide. A lower concentration (0.1 to 100 g/l) is utilized for pickling, and a higher concentration (5 to 300 g/l) for etching and polishing.

The second component, an acid, includes sulfuric, sulfamic, phosphoric, hydrochloric, acetic, hydrofluric, hydroborofluoric, and hexafluorohydrosilicic acids. Among them, sulfuric acid is generally used because it is cheap. Acetic acid is suitable for the dissolution treatment of lead metal and alloys thereof. For such metals as niobium, titanium, stainless steel and other special alloys, hydrofluoric acid should be used either alone or in the form of a mixture with another acid. Thus, acids to be used should be chosen depending on the metals to be treated. The acid concentration in the solutions for chemical treatment of this invention is 0.1 to 10 g/l in terms of hydrogen-ion concentration. If the concentration is below 0.1 g/l, the solution is practically too weak to dissolve metals. On the other hand, however, a solution having an excessive acid concentration, that is over 10 g/l for example, does not exhibit sufficient dissolution power. Solutions having excessively high or low acid concentration should be excluded.

The third component, the compounds which serve to suppress the decomposition of hydrogen peroxide, are (a) alcohol polyoxyethylene ether, (b) alkylsulfonic acid, (c) alkyl hydrogen phosphate, (d) alkyl hydrogen phosphite, (e) alkyl hydrogen sulfate and their salts, and they are represented by the formulae as follows.

a. Alcohol polyoxyethylene ether,

R ₁ O(C ₂ H ₄ O) _n H

wherein R ₁ is an aliphatic hydrocarbon residue having 4 to 20 carbon atoms and n is an integer of 2 to 20;

b. Alkylsulfonic acid,

X -- R ₂ -- SO ₃ H

wherein R ₂ is an alkyl group having 2 to 18 carbon atoms, and X is hydrogen or an alkyl group having 1 to 18 carbon atoms.

c. Alkyl hydrogen phosphate, ##SPC3##

wherein R ₃ is an alkyl group or an alkyl hydroxyalkyl group, each group having carbon atoms of 1 to 12, and R ₄ is hydrogen, or a group or an alkyl hydroxyalkyl group, each group having 1 to 12 carbon atoms.

d. Alkyl hydrogen phosphite, ##SPC4##

wherein R ₃ and R ₄ are the same as R ₃ and R ₄ respectively in the above alkyl hydrogen phosphate;

e. Alkyl hydrogen sulfate,

R ₃ OSO ₃ H wherein R ₃ is the same as R ₃ in the above alkyl hydrogen phosphate.

The concentration of above alcohol polyoxyethylene ether to be added is preferably 0.01 to 20 g/l, and if the concentration is within this range, the following effects that have been already mentioned could be achieved; (1) stabilization of hydrogen peroxide, (2) prevention of mist of the acid from spraying, (3) accelerated rate of dissolution of metals and producing luster on the finished surface. The most preferred concentration is 0.1 to 15 g/l. These effects are particularly predominant when the aliphatic hydrocarbon residue R ₁ in the above formula in (a) is cetyl, oleyl, octadecyl, dodecyl or octyl. If the number of carbon atoms in the aliphatic hydrocarbon residue R ₁ and/or the integer n are/is beyond the specified range, at least one of the effects described in (1), (2) and (3) above is lost. Stabilization of hydrogen peroxide and the rate of dissolution of metals will be explained hereinafter. Ethers (a) are featured by their high surface activity. Since they are nonionic, they form a stable and dense layer of foam on the surface of solutions for dissolution treatment even in the presence of acids and metal salts, serving to prevent mist of acid from spraying.

In the next place, the concentration of alkylsulfonic acid (b) to be added is preferably 0.01 to 20 g/l, more preferably 0.1 to 15 g/l.

The concentrations of alkyl hydrogen phosphate (c), alkyl hydrogen phosphite (d) and alkyl hydrogen sulfate (e) to be added are preferably 0.001 to 20 g/l, more preferably 0.01 to 5 g/l. The alkyl hydrogen phosphate (c), alkyl hydrogen phosphite (d) and alkyl hydrogen sulfate (e) are chemically more stable when alkyl groups are composed of more carbon atoms. But these compounds having too many carbon atoms show less solubility. For this reason the number of carbon atoms is restricted to 1 to 12.

Compounds belonging to the three categories (c), (d) and (e) have the effect of stabilizing hydrogen peroxide and preventing chloride from interfering with the dissolution of metals, even when the compounds exist in a minute quantity. These two kinds of effects will be explained in the following with reference to experimental results.

First, the following experiment was carried out to examine the stabilizing effect on hydrogen peroxide: to a mixed aqueous solution containing 30 g-Cu/l of copper sulfate, 100 g/l of sulfuric acid and 10 g/l of hydrogen peroxide, the compounds (a), (b), (c), (d) and (e) to be used in this invention and conventional stabilizing agents were separately added and the rate of decomposition of hydrogen peroxide was measured at a bath temperature of 60°C. The results are shown in Tables 2 and 3.

Alcohol polyoxyethylene ethers in (a) appear in Nos. 2 through 15 in Table 2. These ethers are not single pure compounds, but the degree of polymerization n of each ether is distributed to some extent; therefore molecular formulae of the major components are shown in the table. Examination of the influence of molecular weight proves that the magnitude of molecular weight exhibits some difference in the effect of stabilization (NOS. 2 to 7). The ethers show remarkable effect on stabilization when added in a concentration exceeding 0.01 g/l (Nos. 8 to 14). Addition of the ether in a concentration of over 20 g/l is too expensive and wasteful. In No. 15 where R ₁ is oleyl group, which is an unsaturated aliphatic hydrocarbon residue, a better effect on stabilization can be seen in comparison with that when lower alkyl alcohol, carboxylic acids, glycerine, sodium pyrophosphate and 8-oxyquinoline, which have been previously used, are added in the same concentration. Nos. 16 through 29 show results when alkyl sulfonic acids (b) are used. In these cases, the effect on stabilization depends on the molecular structure of the compounds and the concentration of the compounds, the situation being just the same as in the case of alcohol polyoxyethylene ether (a). The best result was observed with ethan sulfonic acid. Alkyl sulfonic acids (b) generally exhibit better effect on stabilization than alcohol polyoxyethylene ethers (a) above. The results obtained from the use of alkyl hydrogen phosphate (c) and alkyl hydrogen phosphite (d) are shown in NOS. 30 through 43. The stabilizing effect depends on the concentration of compounds added, number of carbon atoms in the respective alkyl groups and the molecular structure, but the number of alkyl groups has almost nothing to do with such effect. The best stabilizing effect was observed with dibutyl hydrogen phosphate (No. 38) and butyl dihydrogen phosphite (No. 42). In respect to the effect of the concentration of diethyl hydrogen phosphate on the stabilization (Nos. 31 through 36), no significant stabilization effect was seen when the concentration was below 0.0001 g/l, but the rate of decomposition was reduced to 1/10 or less of No. 1, where no compound was added, for the concentration of 0.001 g/l; about 1/30 for 0.01 g/l; less than 1/100 for 0.1 g/l; and about 1/300 for 1 g/l. The stabilizing agents to be used in this invention reduce the rate of decomposition of hydrogen peroxide to less than 1/10 of the decomposition rate attained by the use of conventional agents having the same concentration. This leads to the conclusion that the required amount of alkyl hydrogen phosphate (c) and alkyl hydrogen phosphite (d) is 1/50 to 1/100 of that of conventional stabilizing agents if the same degree of effect is desired.

Nos. 44 through 54 are examples where alkyl hydrogen sulfates (e) are used. The compounds of this category have somewhat less stabilizing effect than phosphate (c) and phosphite (d), but larger effect than ethers (a) and sulfonic acids (b) when used in lower concentrations. As for the influence of molecular structure, a compound having a straight chain exhibits better effect than a compound having a branched chain (Nos. 49 and 51). Needless to say, even the latter compound having a branched chain is much more useful than conventional stabilizing agents. In comparison with conventional stabilizing agents containing an alkyl group, alkyl hydrogen sulfates of the present invention having the same alkyl group are much better with respect to stabilizing effect. This is apparent from comparisons of No. 44 with No. 55, No. 45 with No. 62, No. 49 with No. 58, and No. 51 with No. 59;

It is concluded from the above that the stabilizing agents to be used in the present invention exhibit better effect of stabilizing hydrogen peroxide when added in a lower concentration than conventional stabilizing agents.

Table 2 ____________________________________________________________ ______________ No. Compound added Concentration Rate of of added comp. decomposi- (g/l) tion (g-H ₂ O ₂ /l hr) ____________________________________________________________ ______________ 1 none -- 10.3 2 C ₈ H ₁₇ O(C ₂ H ₄ O) ₆ H 2 0.33 3 C ₈ H ₁₇ O(C ₂ H ₄ O) ₁₀ H 2 0.21 4 C ₁₂ H ₂₅ O(C ₂ H ₄ O) ₁₀ H 2 0.15 5 C ₁₂ H ₂₅ O(C ₂ H ₄ O) ₆ H 2 0.17 6 C ₁₆ H ₃₃ O(C ₂ H ₄ O) ₆ H 2 0.14 7 C ₁₆ H ₃₃ O(C ₂ H ₄ O) ₁₅ H 2 0.27 8 C ₁₆ H ₃₃ O(C ₂ H ₄ O) ₈ H 0.001 9.9 9 " 0.01 2.9 10 " 0.1 0.44 11 " 1 0.16 12 " 10 0.14 13 " 20 0.14 14 " 50 0.17 Stabilizing 15 C ₁₈ H ₃₅ O(C ₂ H 4 O) ₈ H 1 0.23 agents to 16 CH ₃ SO ₃ H 5 0.11 be used 17 C ₂ H ₅ SO ₃ H 5 0.05 in the 18 n--C ₃ H ₇ SO ₃ H 0.001 0.77 present 19 " 0.01 0.63 invention 20 " 0.1 0.19 21 " 1 0.09 22 " 5 0.061 23 " 20 0.069 24 " 50 0.066 25 iso--C ₃ H ₇ SO ₃ H 5 0.090 26 C ₈ H ₁₇ SO ₃ H 1 0.11 27 C _n H _2n +1 SO ₃ Na 1 0.11 (n = 12 - 18) 28 HO ₃ S(CH ₂ ) ₃ SO ₃ H 5 0.13 29 HO ₃ S(CH ₂ ) ₆ SO ₃ H 5 0.07 ____________________________________________________________ ______________

Table 3 ____________________________________________________________ ______________ Concentration Rate of De- No. Compound added of added comp. composition (g/l) (g-H ₂ O ₂ /l hr) ____________________________________________________________ ______________ 30 (CH ₃ O) ₂ P(O)OH 1 0.078 31 (C ₂ H ₅ O) ₂ P(O)OH 0.0001 5.3 32 " 0.001 0.76 33 " 0.01 0.36 34 " 0.1 0.098 35 " 1 0.039 36 " 10 0.043 Stabilizing 37 (C ₂ H ₅ O)P(O)(OH) ₂ 1 0.044 agents to 38 (n--C ₄ H ₉ O ₂ )P(O)OH 0.5 0.024 be used 39 (HO--C ₂ H ₅ O)PO(OH) ₂ 0.5 0.030 in the 40 (C ₂ H ₅ O) ₂ POH 0.5 0.040 present 41 (iso--C ₃ H ₇ O) ₂ POH 0.5 0.059 invention 42 (n--C ₄ H ₉ O)P(OH) ₂ 0.5 0.020 43 (HO--(CH ₂ ) ₂ O) ₂ POH 0.5 0.029 44 (CH ₃ O)SO ₃ H 1 0.29 45 (C ₂ H ₅ O)SO ₃ H 1 0.11 46 (n--C ₃ H ₇ O)SO ₂ H 0.001 2.1 47 " 0.01 0.38 48 " 0.1 0.098 49 " 1 0.059 50 " 10 0.055 51 (iso--C ₃ H ₇ O)SO ₃ H 1 0.21 52 (n--C ₄ H ₉ O)SO ₃ H 1 0.041 53 (C ₈ H ₁₇ O)SO ₃ H 1 0.066 54 (HO--(CH ₂ ) ₄ O)SO ₃ H 1 0.071 Conventional 55 CH ₃ OH 1 1.1 Stabilizing 56 C ₂ H ₅ OH 1 0.71 agents 57 " 10 0.25 58 nC ₃ H ₇ OH 2 0.28 59 iso--C ₃ H ₇ OH 5 0.64 60 C ₈ H ₁₇ OH 1 1.2 61 (HO)CH ₂ --CH(OH)--CH ₂ (OH) 5 2.0 62 C ₂ H ₅ COOH 1 0.27 63 Na ₄ P ₂ O ₇ 10 1.5 64 8-oxyquinoline 1 9.8 ____________________________________________________________ ______________

Subsequently, the effect of the stabilizing agents to be used in the present invention was investigated on accelerating the rate of dissolution of metals and reducing the interference of chloride ions with the dissolution. Thus, a variety of the stabilizing agents referred to above, the third component to be used in this invention, together with chloride ions were each added separately to an aqueous solution containing 100 g/l of sulfuric acid and 45 g/l of hydrogen peroxide, and the rate of dissolution of yellow brass plates (Cu : Zn = 65 : 35 by weight percent) was measured at a bath temperature of 20°C. The rate of dissolution is shown in Table 4 in relative values against the basic figure of 100 for the rate obtained when neither stabilizing agent nor chloride ion was added. Alcohol polyoxyethylene ether (a) accelerates the dissolution more than twice as much as when no additives are used, as seen in No. 4 and No. 6, but the accelerating effect is remarkably lost when only 10 ppm of chloride ions are present, though the rate of dissolution (129) is still about twice as much as the rate of dissolution (67) obtained when no stabilizing agent was added (No. 2).

As is apparent in Nos. 7 through 11, alkyl sulfonic acids (b) and alkyl hydrogen phosphates (c) show little accelerating action toward dissolution of metals, but exhibit considerably large effect in reducing the interference of chloride ions with dissolution rate.

As can be seen in Nos. 14 and 15, the dissolution rate is considerably accelerated with the interference of chloride ions being suppressed, when the ethers (a) above are used together with the phosphates (c) or the sulfonic acids (b). Alkyl hydrogen sulfates (e), on the other hand, tend somewhat to supress the rate of dissolution, but they are entirely free from influence of chloride ions even if the quantity of the latter is large, as is evident in Nos. 12 and 13. Therefore, it is readily understood from Nos. 16 and 17 that a sufficiently high level of acceleration of dissolution rate could be achieved when sulfates (e) and ethers (a) both mentioned above are used in combination.

As is evident from the foregoing descriptions, the third component of this invention not only accelerates dissolution of metals, but also eliminates the interference of chloride ions, present in city water and other water, with dissolution of metals, which has been the fatal drawback of solutions for chemical dissolution which has been the.

Therefore, the third component to be used in the present invention may be at least one compound selected from the five groups of compounds mentioned above, that is alcohol polyoxyethylene ethers (a), alkyl sulfonic acids (b), alkyl hydrogen phosphates (c), alkyl hydrogen phosphites (d) and alkyl hydrogen sulfates (e). Particularly when alcohol polyoxyethylene ethers (a) are used in combination with a compound selected from the four groups of compounds (b), (c), (d) and (e), three major drawbacks inherent in conventional solutions for chemical dissolution treatment of metals could be readily avoided; that is (1) decomposition of hydrogen peroxide, (2) spraying of mist of acid and (3) decrease in dissolution rate of metals.

Table 4 ____________________________________________________________ ______________ Concentration Concentration Relative No. Compound added of added comp. of Cl ^- (ppm) dissolu- (g/l) tion rate ____________________________________________________________ ______________ 1 none -- 0 100 2 " -- 10 67 3 " -- 300 48 4 C ₁₂ H ₂₅ O(C ₂ H ₄ O) ₁₀ H 5 0 220 5 " " 10 129 6 C ₁₆ H ₃₃ O(C ₂ H ₄ O) ₆ H 2 0 205 7 C ₂ H ₅ SO ₃ H 2 0 111 8 " " 300 108 9 (n--C ₄ H ₉ O) ₂ P(O)OH 1 0 137 10 " " 10 129 11 " " 300 133 12 C ₂ H ₅ OSO ₃ H 1 0 85 13 " " 300 86 14 C ₁₂ H ₂₅ O(C ₂ H ₄ O) ₁₀ H 2 0 205 (N--C ₄ H ₉ O) ₂ P(O)OH 0.5 15 " 300 171 16 C ₁₂ H ₂₅ O(C ₂ H ₄ O) ₁₀ H 2 0 201 C ₂ H ₅ OSO ₃ H 0.5 17 " " 10 166 ____________________________________________________________ ______________

When bars or tubes of yellow brass material in a bundle are immersed in a solution for chemical dissolution treatment consisting of the three components (acids, hydrogen peroxide and stabilizing agent) mentioned above, so-called "red stain" may often be generated at the contact area of the materials. "Red stain" is a result of dezincfication peculiar to yellow brass materials by which the surface partly assumes copper color. This phenomenon may very often happen when the materials are kept immersed for a long time in an unstirred bath which is lacking in hydrogen peroxide. This is the fourth drawback occurring in conventional solutions for chemical dissolution treatment.

The fourth drawback of conventional solutions could be eliminated, according to the investigation of this invention, by adding 0.1 to 5,000 ppm, preferably 1 to 500 ppm, of glue or gelatine as the fourth component. Since glue and gelatine are subject to hydrolysis to some extent while in use, it may be possible to use partly hydrolyzed glue or gelatine (hydrolyzates). The theory of the function of these added matters is not evident. But, if the "red stain" is generated following the "dissolution-deposition theory", it is considered that they function to suppress the deposition reaction of copper.

As has been explained above, the solutions for chemical treatment of metallic materials can be utilized for treatments of various metallic materials: pickling, etching, chemical milling and chemical polishing. There is no specific limitation to metals to which the treatment solutions of this invention can be applied. The metals include copper, silver, nickel, iron, zinc, aluminum, titanium and the alloys thereof, such as brass, nickelsilver, cupronickel and copper-titanium alloys. When applied to copper and the alloys thereof, the present invention exhibits the best results.

Among the chemical dissolution treatments referred to above, pickling is suited to a relatively low concentration (0.1 to 100 g/l) of hydrogen peroxide, while etching and chemical milling are suited to a relatively high concentration (5 to 200 g/l) of hydrogen peroxide. Chemical polishing is performed by immersing materials to be treated in a specially concentrated solution (10 to 300 g/l) for a short time, where the following procedure is particularly desired for copper and copper alloys: in a solution of this invention in which the concentration of hydrogen peroxide exceeds 5 g/l and the ratio by weight of hydrogen peroxide to hydrogen ion concentration, H ₂ O ₂ /[H ⁺ ], is over 30, copper or a copper alloy is immersed to form a colored coating film of oxide, and then immersed in a solution which dissolves the copper oxide such as solutions of dilute acids, ammonia, aminocarboxylic acid and sodium cyanide, to dissolve the colored coating film of oxide. Since hydrogen peroxide is stabilized by the action of the third component used in this invention, a uniformly colored coating film of oxide is formed without being disturbed by bubbles of gas evolving as a result of decomposition, and therefore a uniformly lustrous surface is provided. Further, as the range of solution composition in which the colored coating film of oxide is formed can be expanded by adding the third component, the treatment can be performed in a stable manner and on a large scale.

The present invention will be more clearly understood from the following examples.

EXAMPLE 1

A hot rolled copper wire rod (8 mm diameter) having 0.3 percent by weight of black oxide scale was immersed for 5 min. in a solution of the following composition: H ₂ O ₂ 2 g/l H ₂ SO ₄ 50 g/l C ₁₂ H ₂₅ O(C ₂ H ₄ O) ₆ H 5 g/l (main constituent) Cl ^- <1 ppm Bath temperature about 40°C

The oxide scale completely disappeared, and a semi-lustrous clean surface was obtained with no deposition of tiny powder of copper.

Comparison 1

The same wire rod as in Example 1 was immersed in a solution containing 50 g/l of sulfuric acid at 40°C. In 5 min. half of the scale remained but the scale was completely removed only in 30 min. Tiny powder of copper which deposited on the surface was expelled by a water jet, leaving a mat surface.

Comparison 2

The same wire rod as in Example 1 was immersed in a solution which was the same as in Example 1 except that alcohol polyoxyethylene ether containing C ₁₂ H ₂₅ O(C ₂ H ₄ O) ₆ H as main constituent was not contained in the solution. The oxide scale remained in 5 min., but disappeared in 10 min. Although deposition of tiny powder of copper was not observed, the surface was not lustrous.

EXAMPLE 2

The same wire rod as in Example 1 was immersed in a solution prepared with city water and having the following composition:

H ₂ O ₂ 2 g/l H ₂ SO ₄ 50 g/l C ₁₂ H ₂₅ O(C ₂ H ₄ O) ₆ H 5 g/l (main constituent) Cl ^- ppm Bath temperature about 40°C

The black scale that was observed in 5 min. disappeared in 10 min. The surface with no deposition of tiny powder of copper was semi-lustrous and clean.

Comparison 3

The same wire rod was immersed in the same solution as in Example 2 except that C ₁₂ H ₂₅ O(C ₂ H ₄ O) ₆ H as main constituent was not contained in the solution. The black scale remained in 10 min. but disappeared in 20 min. Although no tiny powder of copper was observed on the surface, the surface was not lustrous.

EXAMPLE 3

The same wire rod was immersed in the same solution as in Example 2 except that 0.5 cc/l of ethyl hydrogen sulfate was further contained in the solution. The black scale disappeared in 5 min. and the surface obtained was semi-lustrous without deposition of tiny powder of copper.

EXAMPLE 4

A copper-titanium alloy strip containing 4 percent by weight of titanium was heated for 7 min. in the air at 850°C and quickly cooled to make it soft, when a primary scale of black copper oxide as major constituent and an approximately 4μ thick light brown sub-scale which resulted from internal oxidation of titanium were formed. The former scale was removed when cooled quickly.

The copper strip having the sub-scale was immersed for 2 min. in the solution having the following composition: H ₂ O ₂ 30 g/l H ₂ SO ₄ 200 g/l (n--C ₄ H ₉ O) ₂ PO(OH) 1 g/l Bath temperature about 20°C

The light brown sub-scale disappeared and silvercolored surface of the alloy came out.

The metal was conventionally treated using a mixed aqueous solution containing sulfuric acid and sodium dichromate, where treatments of the waste solution containing harmful hexavalent chromium ions caused a serious problem with respect to pollution. Further the dissolved copper could not be recovered because a large amount of chromium coexisted in the solution.

In the process of this invention, however, the waste solution was easily cleaned by neutralization with alkali, and then copper in the solution could be recovered by means of electrolysis from the waste solution.

EXAMPLE 5

A yellow brass strip (Zn : 35 wt. percent) was heat treated at 550°C in an atmosphere of Kerosene decomposition gas for 1 hour and yellow brown oxide scale was formed. Almost all of the scale consisted of zinc oxide and there existed a thin layer caused by dezincfication (<1μ) on the surface of alloy in contact with the scale.

The strip was immersed for 15 sec. in the solution of the following composition and a bright surface of yellow brass was obtained.

______________________________________ H ₂ O ₂ 15 g/l H ₂ SO ₄ 80 g/l C ₁₆ H ₃₃ O(C ₂ H ₄ O) ₆ H 2 g/l n--C ₃ H ₇ SO ₃ H 0.1 g/l Bath temperature about 20°C ______________________________________

The surface analysis by an electron probe micro-analyzer showed 35 wt. percent of zinc, agreeing with the initial alloy composition.

EXAMPLE 6

Twenty cartridge brass tubes (Zn 30 percent) of 1 inch in outer diameter, that had been treated in the same atmosphere as in Example 5, were made into a bundle and hung with a copper wire in the solution having the following composition for 5 min,:

H ₂ O ₂ 7 g/l H ₂ SO ₄ 100 g/l C ₁₆ H ₃₃ O(C ₂ H ₄ O) ₆ H 2 g/l (iso--C ₃ H ₇ O) ₂ POH 0.5 g/l Glue 25 ppm Bath temperature about 25°C

A bright surface of yellow brass was obtained. No problem was observed at the contact parts of the tubes.

Comparison 4

The same bundle of pipes was immersed for 5 min. in a solution of the same composition as in Example 6 except that the solution did not contain glue. Lustrous pipe surfaces without any fault were obtained.

However, when the procedure was repeated until the hydrogen peroxide content decreased below 5 g/l, stripes of copper color, that is "red stain," were developed along the contact area of the pipes. Addition to this treating solution of glue in an amount of 25 ppm was successful in eliminating the red strains.

EXAMPLE 7

A silver-plated oxygen-free copper sheet which had been processed for a lead frame for integrated circuits, was immersed for 40 sec. in a solution of the following composition: H ₂ O ₂ 20 g/l H ₂ NSO ₃ H 100 g/l C ₁₆ H ₃₃ O(C ₂ H ₄ O) ₁₂ H 2.5 g/l Bath temperature about 20°C

The sheet, plated with silver to a thickness of 3μ, was heat treated at 290°c for an hour, but no blister was observed on the plated surface.

Conventionally, a mixture of acids, i.e., 1 part of nitric acid with 3 parts of phosphoric acid, has been used and evolution of harmful nitrogen oxide gas has been a serious problem.

EXAMPLE 8

The same sheet as in Example 7 was immersed for 30 sec. in a solution of the following composition:

H ₂ O ₂ 35 g/l H ₂ SO ₄ 150 g/l n--C ₃ H ₇ OSO ₃ H 1 g/l Bath temperature about 20°C

The sheet was then plated with silver in the same manner and tested for thermal resistance, but no problem was observed in the regard.

EXAMPLE 9

A yellow brass sheet (Zn : 35 wt. percent) was immersed for 3 min. in an aqueous solution at room temperature (20°C) containing 5 g/l of alcohol polyoxyethylene ether, where C ₁₈ H ₃₃ O(C ₂ H ₄ O) ₈ H was the main constituent, and hydrogen peroxide and sulfuric acid were adjusted as shown in Table 5 (first stage of operation). The sheet was then immersed for 5 sec. in a dilute solution of sulfuric acid (3 percent) (second stage of operation), and dried after being washed with water.

When a gold coating film was formed in the first stage of operation, a mirror-like bright surface was produced in the second stage of operation; these cases are indicated by "O" in the table. If a coating film was not developed in the first stage of operation, no change occurred in the second stage of operation and a non-lustrous surface resulted; these cases are shown by x in the table.

In conclusion, a mirror-like bright surface could be obtained when the ratio by weight of hydrogen peroxide to the hydrogen ion concentration in the sulfuric acid exceeded 30.

Table 5 ______________________________________ Concentration Concentration of H ₂ O ₂ (g/l) of H ₂ SO ₄ (g/l) 10 20 30 50 75 100 ______________________________________ 25 x O O O O O 50 x x O O O O 75 x x x O O O 100 x x x x O O ______________________________________

EXAMPLE 10

A pure copper sheet was immersed for 1 min. in a solution of the following composition:

H ₂ O ₂ 60 g/l H ₂ SO ₄ 20 g/l (C ₂ H ₅ O) ₂ P(O)OH 2.5 g/l C ₂ H ₅ SO ₃ H 2.5 g/l

When a brown coating film was removed by dissolution by immersion in an ammoniacal water (2 percent) for 30 sec., a mirror-like bright surface was obtained.

EXAMPLE 11

To etch a pure nickel sheet, the sheet was kept immersed in a solution of the following composition under stirring and the rate of dissolution was measured.

______________________________________ H ₂ O ₂ 60 g/l H ₂ SO ₄ 150 g/l CH ₃ SO ₃ H 2.5 g/l Bath temperature about 60°C ______________________________________

The rate of etching was 15 mg.cm ² × min. The rate of etching in an aqueous sulfuric acid solution (150 g/l) at 60°C was as small as 0.003 mg/cm ² × min.

EXAMPLE 12

A low-carbon steel sheet produced a bright surface when it was immersed for 30 sec. in a solution of the following composition: H ₂ O ₂ 150 g/l H ₂ SO ₄ 280 g/l C ₁₂ H ₂₅ O(C ₂ H ₄ O) ₁₂ H 2 g/l (n--C ₄ H ₉ O) ₂ P(O)OH 0.5 g/l Bath temperature about 20°C

Hitherto, a mixed aqueous solution of sulfuric, phosphoric and nitric acids was used at a temperature over 60°C, where evolution of nitrogen oxide gas and treatment of waste solution were a serious problem of environmental pollution.

EXAMPLE 13

In preparing a titanium wire to be used as electrode for electrolysis, a titanium wire carrying oxide scale was drawn to 2.0 mm diameter, then immersed for 30 min. in a molten caustic soda bath at 420°C, and finally cooled quickly in water to remove the thick scale. The wire with a thin oxide film on the surface was immersed for 30 sec. in a solution of the following composition:

H ₂ O ₂ 15 g/l HF 30 g/l n--C ₃ H ₇ SO ₃ H 1 g/l Bath temperature about 20°C

The product had a coarse surface, which was desirable for use as electrode material.

EXAMPLE 14

In preparing a titanium wire for corrosion-resistant networks the same raw material titanium metal as in Example 13 was drawn to 1.5 mm diameter, and treated in a molten caustic soda bath to remove the thick scale. Subsequently, the wire was immersed for 3 min. in a solution having the following composition. The surface of the wire became smooth and lustrous.

______________________________________ H ₂ O ₂ 80 g/l HF 25 g/l C ₁₂ H ₂₅ O(C ₂ H ₄ O) ₁₂ H 5 g/l n--C ₄ H ₉ OSO ₃ H 0.5 g/l Bath temperature about 20°C ______________________________________

EXAMPLE 15

A high speed steel sheet, when immersed for 15 sec. in a solution having the following composition, gave a bright surface.

______________________________________ H ₂ O ₂ 50 g/l HF 100 g/l H ₃ PO ₄ 100 g/l n--C ₃ H ₇ SO ₃ H 5 g/l Bath temperature about 60°C ______________________________________