US3460953A - Process for depositing brasslike coatings and composition therefor - Google Patents

Description

United States Patent U.S. Cl. 1061 Claims ABSTRACT OF THE DISCLOSURE An immersion process and a composition for applying a brasslike finish to steel by immersing steel in a bath comprising copper, nickel, and tin, together with a complexing agent of the group of boric acid and citric acid, and an enhancing agent of the group of glutaric acid, succinic acid, glycolic acid, their anhydrides, and their water soluble salts.

This invention relates to immersion electrolytic plating, and more particularly to electrolytes therefor.

An important object of the invention is to provide plating electrolytes for use in plating brasslike coatings on objects, which coatings .are substantially similar in appearance to those generally known as liquor finish, and employing a tertiary system of cupric, nickelous and stannous salts.

Another important object of the invention is to provide new and useful immersion electrolytic plating electrolytes containing new additions, functioning as complexing and chelating agents for the plating of a metal or metals.

Still another important object of the invention is to provide a new and useful immersion electroplating electrolyte, containing enhancing and modifying agents for the complexing and chelating agents.

The added agents improve the thickness, density, adhesion, appearance and anti-tarnishing characteristics of the plated objects.

In addition, an important object of the invention is to provide immersion electrolytic plating electrolytes which tend to slow the build-up of iron salts in the electrolytes, whereby the useful lives of the electrolytes are lengthened.

Another important object of the invention is to provide new and useful immersion electrolytic plating electrolytes which contain low to moderate cost compounds which are readily obtainable and which may be incorporated in a sulfuric acid-containing electrolyte by conventional steps, whereby the electrolytes may be produced and marketed at moderate prices.

An additional object of the invention is to provide several chemical classes of brightening agents which function in these electrolytes to enhance, improve, and brighten the coating obtained.

Other objects and advantages of the invention will be apparent during the course of the following detailed description of the invention.

A preferred example of my complexing and chelating agents is boric acid, and preferred examples of my enhancing and modifying agents are glutaric anhydride, sodium glycolate and succinic anhydride. Examples of brightening agents include 3-amino-lH-1, 2,4-triazole and Z-butyne-l, 4-diol. Examples of the plating salts are "ice those of copper, nickel and tin, either employed together, any two, or separately. An example of the objects to be placed are iron or steel wires or rods.

Numerous classes of chemical compounds have been found to enhance, improve, and brighten the deposited coating. Among these are: magnesium salts, for example magnesium chloride; short chain 'monobasic carboxylic acids, for example formic acid, or the corresponding sodium or potassium salts, for example sodium acetate and sodium formate; fluorboric acid and its salts, for example sodium fluorborate; benzimidazoles, for ex ample Z-methyl-benzimidazoles; aldchydes, for example paraformaldehyde; triazoles, for example 3-amino-l H- 1,2,4-triazole; piperazines, for example 2-methylpiperazine; and acetylenic diols, for example 2-butyne-1,4- diol. It is, of course, obvious that these are specific examples that the general classes of compounds including carboxylic acids, fiuorboric acids, aldehydes, acetylenic diols, triazoles, benzimidazoles, piperazines, and related classes of compounds would tend to function to enhance, improve, and brighten coating to some extent.

Although I consider glutaric anhydride, sodium glycolate and succinic anhydride as my preferred enhancing and modifying agents, I have experimented with other agents including citric acid, gluconic acid, succinic acid, ethylenediamine tetracetic acid. These are only specific examples, the series of related acids including tartaric, fumaric, maleic, propionic, butyric, valeric, and other similar acids are adaptable. I have discovered that, especially, glutaric anhydride, sodium glycolate and succinic anhydride, in combination with for example, boric acid, citric acid or hydroxy acetic acid, impart synergetic effects to the complexing and chelating agents employed, since the qualities of the plating are enhanced over those where any one member of one group or one member of the other group are employed.

In the following examples of formulae, the preferred grade of boric acid is U.S.P.;- of glutaric anhydride, the the technical grade and sodium glycolate, the purified grade. The sulfuric acid of the electrolyte is preferably conventional 66 Baum in tap water, with the grades of the salts of the plating metals those commonly used in immersion electrolytic plating electrolytes.

Since very superior platings result from the use of boric acid associated with glutaric anhydride in my formulations, the following Example I is given.

EXAMPLE 1 Consisting of a dry admixture of the following composition to be used in aqueous solution of suitable concentration to produce an immersion coating on steel objects, the percentages of specific ingredients in this and the other examples are by weight, except as noted herein- In place of glutaric anhydride, I may substitute sodium ride in an immersion plating bath consisting of boric acid, glycolate as follows: nickel sulfate, copper sulfate, and stannous chloride modi- EXAMPLE 2 fies, enhances, and brightens the deposited coating. This concept is illustrated in Example 5 in which the' ratios Specific Specific Dry 5 are merely specific examples of the genreal principle. Example, Admixture,

percent percent EXAMPLE 5 Boric acid 4. 38.1 Specific Specif c Dry Sodium glycolate 2.0 19. 0 Example, Admlxture, Copper sulfate 1. 0 9. Percent Percent Nickel sulfate 3. 0 8. 6 Stannous chloride (anhyd. 0.5 4.8 5.0 47.6 Sulfuric acid 0.5 1. 0 9. 5 Water 89. 0 1. 0 9, 5 3.0 28.6 100. 0 100. 0 stannous chloride (anhyd.). 0.5 4i8 Sulfuric acid Water 89.5 Instead of the glycolate or anhydride, I may substitute l5 citric acid, as follows: 100 0 0 EXAMPLE 3 The sodium chloride may be of any grade from U.S.P.

XV to table salt. S ecific S ecific Dry Exgmpley Xdmixture, Three mod1ficat1ons of the foregoing formulae are percent percent contained in Examples 6 to 8. One illustrates the modification, improvement, enhancement, and brightening pro- Boric acid Citric acid... duced by the incorporatlon of succinic anhydride in an Copper sulfat Nickel sulfate. 1mmers1on plating bath consisting of citric acid, copper,

nickel and stannous salts. The second and third are examples of the modification, improvement and enhancement resulting from the incorporation of either hydroxy acetic acid, or citric acid in an immersion plating bath consistin of Rochelle salts co er, nickel and stannou Or, in place of the above, I may substitute succmlc salm O pp S acid, as follows:

stannous chlon EXAMPLE 4 EXAMPLE 6 ercent Percent percent Percent Boric acid. 0 1 Citric acid 5. 0 47. s Succimc ld- 0 0 Succinic anhydride- 1. 0 9. 5 Copper sulfate. 1. 0 9. 5 Copper sulfatem. 1. 0 9. 5 Nickel sulfate.. 0 6 Nickel sulfate 3. o 28.6 st nnc ciflond y J- 5 8 Stannous chlorid 0. 5 4. s Sulfuric acid 5 Water 89. 5 Water 0 100.0 100 0 100 0 m0 0 EXAMPLE 7 Alternatively, in place of succinic acid, I may substitute diglycolic acid, Rochelle salt, gluconic acid, salicylic Ell a fl lg i ii ifi tr acid, ethylenediamine tetraacetate, or sodium chloride. Percent: Percent As a reduction to practice Of the PI'O and Practice 11 1 11 11; 5,0 47, exemplified by the formulation containing boric acid C tr c acid 1.0 9.5 and glutaric anhydride, 100 milliliters of an eig -p i?5s%ii %f:: 3313:: $13 233 by weight solution of the electrolyte of Example 1 was stannous chloride yd-L. 4:8 prepared. Mild steel panels 20 gauge, 601d r ll 1 y Water 89'5 2 inches were coated by immersion in this solution for 100.0 100.0 three minutes, after about 65 panels had been coated, EXAMPLE 8 4 percent by weight of Example 1 was added to replenish the bath. The color and brightness of the Specific p i c coating was found to be excellent after 728 panels had i e ib iit tififlf'ii iiiii been coated in 100 milliliters of this solution in this manner. The solution was analyzed before use and after figf ifi ffiig ggg -g $33 3:8 728 panels for boric acidby manitol titration, nickel by o p sulfate 1.0 9.3 dimethyl glyoxime, copper by thiosulfate titration after Nmkelsulfate ,12 11% 89.2

separation on aluminum foil, tin by precipitation from nitric acid solution and iron by cupferron precipitation, 10m 1000 the steps resulting in the following:

Additional examples in which succinic anhydride or Aft 728 P 1 Before Use, Percent er ,3 23 dlglYCOllC acid are employed are. Boric acid. 4.51 4. EXAMPLE 9 Specific S ecific Exampl Dry A zlmix- Percent ture, Percent lNeglielble- Born; acid 5.0 47.6 After 200 panels, the copper indicated by titration was Q8 3:2 0.0095 and after 300 panesl, 0.025% expressed as 1.2 9.5 metallic copper. Variations observed may be partly due 8: if to the complexity of the analytical procedure. 100 0 100 0 It was observed that the incorporation of sodium chlo- EXAMPLE 10 Specific Specific Example, Dry Admir- Percent ture, Percent Boric acid 5. 47. 6 Diglycolie acid 1. 0 9. Nickel sulfate 3. 0 28. 6 Copper sulfate 1. 0 9. 5 Stannous chloride (anhyd 0. 5 4.8 Water 89. 5

as below:

EXAMPLE 1 1 Specific Specific Example, Dry Admix Percent ture, Percent Sodium citrate 1. 5 25. 0 Versene 1. 0 16. 7 Copper sulfate 1. 0 16. 7 Stannous chloride (anhyd 1. 0 16. 7 Sodium glycolate 0.5 8.2 Sodium chloride 1. O 16. 7 Sulfuric acid (by volume) 0.5 Water 93. 5

Example 12 Specific Specific Example, Dry Admix- Percent turg, Percent Adherence of the plated coating was excellent at 8.4 and 10.0% iron.

A further binary metal plating formula is as follows, employing succinic acid:

Example 13 Specific Specific Example, Dry Admix- Percent ture, Percent Boric acid 5 50 Brightening agents were evaluated in the following bath:

Percent Boric acid 4 Citric acid 2 Nickel sulfate 3 Copper sulfate 1 Stannous chloride (anhyd.) 0.5

The preferred concentration ranges in solution were:

Magnesium chloride 0.25 to 1.5%. Benzimidazole 0.05 to 0.5%. Z-methylbenzimidazole 0.05 to 0.5%. 2-methylpiperazine (70% soln.) 0.01 to 0.25%. 2-butyne-1, 4- diol 0.1 to 0.25% or saturation. Paraformaldehyde 0.01 to 0.2% or saturation. 3-amino-1H-1,2,4-triazole 0.01 to 0.25%. Sodium acetate 0.01 to 1% or saturation. Sodium formate 0.01 to 1% or saturation. Sodium fluorborate 0.01 to 1% or saturation.

As an addition to the above generalized formulation, the optional brightening agent range may be 0.001 to 1%.

By the term complexing and chelating agent in the claims, is meant one that exhibits chemical sequestering characteristics added to chelating characteristics which affect the metal salts during plating. Enhancing and modifying agent is one that affects the complexing and chelating agent so that the desirable results described in the fourth paragraph of this specification are achieved. By the term brightening agents is meant materials whose principal function in the plating bath seems to be to improve the appearance of the deposited coating, by imparting luster or brightness to the coating.

The actual steps in employing in immersion electroplating by the use of the new electrolytes of this invention are those generally used in the art.

In the above examples, the nickel sulfate is preferably the material termed hexahydrate (6H O) and the copper sulfate is preferably the material termed pentahydrate (SH O).

What is claimed is:

1. An immersion process for applying a brasslike liquor finish to steel which comprises immersing steel in an aqueous solution containing from about 0.01% to about 10% by Weight of a water soluble salt of copper, nickel, and tin, from about 0.5% to about 10% of a complexing agent which is a member of a group consisting of boric acid and citric acid, and from about 0.01% to ab ut 5% of an enhancing agent which is a member of the group consisting of glutaric acid, succinic acid, and glycolic acid, their anhydrides and water soluble salts.

2. A process as in claim 1 where the complexing agent is boric acid and the enhancing agent is glutaric anhydride.

3. A process as in claim 1 where the complexing agent is boric acid and the enhancing agent is sodium glycolate.

4. A process as in claim 1 where the complexing agent is boric acid and the enhancing agent is succinic acid.

5. A process as in claim 1 where the complexing agent is citric acid and the enhancing agent is sodium glycolate.

6. A composition comprising a mixture of dry ingredients suitable for addition to water to prepare an immersion coating solution for steel objects comprising on a parts by weight basis from about 5% to about 10% of a water soluble copper salt, from about 25 to about 30% of a Water soluble nickel salt, from about 3% to about 5% of a water soluble tin salt, from about 25% to about 50Z of a complexing agent selected from a group of boric and citric acids, and from about 10% to about 25% of an enhancing agent selected from a group consisting of the free acid, its salt, or the anhydride of glutaric, succinic, and glycolic acids. 1

7. A composition as in claim 6 where the complexing agent is boric acid and the enhancing agent is glutaric anhydride.

7 8 8. A composition as in claim 6 where the complexing 3,032,486 /1962 821110 et a1 20443 agent is boric acid and the enhancing agent is sodium gly- 3,149,057 9/1964 Parker et a1 204-43 XR colatc. 3,149,058 9/ 1964 Parker et a1 204-43 XR 9. A composition as in claim 6 where the complexing 3,211,578 1965 Gutzeit 106-1 agent is boris acid and the enhancing agent is succinic 5 3,380,898 4/1968 Danemark et a1. 20444 acid.

10. A composition as in claim 6 where the complexing FOREIGN PATENTS agent is citric acid and the enhancing agent is sodium gly- 1,162,398 9/1953 France 601m 871,276 6/1961 Great Britain.

References Great UNITED STATES PATENTS OTHER REFERENCES 570,554 11/1896 Jordis 204-44 IBMT h 1 D 1 B 11 1 4 N 2,081,630 5/1937 Leonard 1O6 1 XR April 19;; me we osure u e 1n, vo o. 11, p. 10, 3,346,404 10/1967 Gardner et a1. 1061 1,837,835 12/1931 Pinner et a1. 20443-XR JOHN MACK Primary Examiner 2,411,674 11/1946 Wilson 20452 437 355 3 1943 Stareck 204 52 KAPLAN, Asslstallt EXamlIlel' 2,653,128 9/1953 Brenner et a1. 20443 U S Cl X R 2,773,818 12/1956 Moy et a1 Z0449 2,882,208 4/ 1959 Becking et a1 20449 117130; 20444,