JPS6191385A - Black electroplating bath - Google Patents

Abstract

PURPOSE:To obtain a black electroplating bath for forming bright and black plating having superior corrosion resistance by adding an amine compound to the electroplating bath having adjusting pH and incorporating a cobalt salt, a stannous salt and an alkali metallic gluconate each at a specified concn. CONSTITUTION:The electroplating bath contg. 3-25g/l (expressed in terms of Co) cobalt salt, 0.1-25g/l (expressed in terms of Sn) stannous salt and 30-150g/l alkali metallic gluconate or glucoheptoate as principal components is adjusted to 7.0-10.0pH with a aqueous ammonia soln., and an amine compound is added to the bath to obtain the black electroplating bath. A hydroxylalkylamine such as monoethanolamine or a polyhydroxylalkylamine such as diethanolamine is used as the amine compound.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to an electroplating method, in which additives are added to an electroplating bath containing cobalt, tin, etc. to produce glossy black plating with excellent corrosion resistance. The present invention relates to a black electroplating bath that can obtain the following properties.

Conventional technology> As this type of black plating, black chromium plating, black nickel plating, and black nickel-tin alloy plating using nickel and tin have been developed.

<Problems to be solved by the invention> In the conventional black plating mentioned above, black chromium plating requires low temperatures, large currents, and hexavalent chromium is released in wastewater, which causes problems in treatment, etc. Furthermore, black nickel plating has poor mechanical strength and has problems with corrosion resistance, discoloration, etc. Furthermore, odor caused by sulfur-containing amino acids has been a problem in black nickel-tin alloy plating.

<Means for Solving the Problems> The present invention has been developed in view of the above-mentioned conventional problems. is 3 to 25 g/1 as a metal, and 0.0 g/1 of stannous salt as a metal.
A basic electroplating bath (hereinafter referred to as basic bath) containing 1 to 25 g/l and 30 to 150 g/l of an alkali metal salt of gluconic acid or glucoheptonic acid, and further adjusting the pH to 7.0 to 10.0 with aqueous ammonia. ) with amine compounds,
This is an attempt to solve the above conventional problems by adding sulfur-containing compounds, zinc ions, etc. as additives.

Effect> In the present invention, cobalt ions, tin ions, gluconic acid ions, or glucoheptonate ions are added as alkali metal salts to a basic bath containing ammonium and sodium or potassium.

First of all, it is better to add a large amount of cobalt to obtain a black color, but if it is too large, it may precipitate in the bath or cause an imbalance with tin, so the cobalt ion should be 6 to 18 g/
It is preferable.

Since tin depends on the amount of cobalt added, less is better; if it is too much, the white glossy alloy plating will spread from the bottom mold flow area to the high current area, and in some areas, black and white will alternate in a comb-like pattern. appears in

The preferred amount of gluconic acid ion is 45 to 70 g/l, and it depends on the amount of metal, but if gluconic acid is in excess, the color tends to be pale, and if it is in a small amount, metal precipitation will increase.

As for alkali metals, the amount of sodium ions and potassium ions does not matter, but there is a suitable range for ammonium ions; if there are too few, the plating will not be uniform, and if there are too many, the plating will become pale black.

Therefore, considering the above-mentioned characteristics, the components in the bath should be 3 to 25 g/l of cobalt salt as metal, 0.1 to 25 g/l of stannous salt as metal, and 0.1 to 25 g/l of alkali metal salt of gluconic acid or glucoheptonic acid. It is contained in a concentration range of 30 to 150 g/β, and the pH is adjusted to 7.0 with aqueous ammonia.
The basic bath is adjusted to a range of 0 to 10.0.

Next, an amine compound is added to the basic bath, and hydroxyalkylamine, polyhydroxyalkylamine, or these are reacted with epihalohydrin, dihalohydrin, etc. There are compounds. Hydroxyalkylamines include monoethanolamine and monoisopropanolamine, and polyhydroxyalkylamines include jetanolamine, triethanolamine, diisopropanolamine, quatrol, and the like.

Black plating can be obtained by adding these amine compounds to the basic bath, but there are other sulfur-containing compounds as additives to further deepen the color tone and improve coverage. Compounds include sulfur-containing amino acids and sulfur-containing alkyl amines.Sulfur-containing amino acids include cystine and methionine, and when added to the bath, effects such as deepening the color tone can be observed.However, it has a characteristic odor. It is unavoidable that sulfur-containing alkylamines contain 2,5
-dimercapto・1.3.4-thiodiazole, 2-mercaptohendithiazole, ethylenethiourea, dithiouralel, 6-mercapto・2-aminopurine, 5-
Examples include mercapto/2-aminopurine, 2-mercaptobenzoxazole, 2-mercaptoethylamine, 6-thioguanine, 6-mercaptopurine, thiouracil, and the like. When these are added, a new chelate is formed from cobalt and tin with sulfur and nitrogen, and there is no sulfur-based odor, only a slight odor from the added ammonia, so it is safe to use during work. is in good condition.

Other additives include surfactants such as polyethylene oxide, polypropylene oxide, block polymers, sonylphenol ethylene oxide, octylphenol ethylene oxide, and polyethylene oxide leyl ether. These are 0.01 to Ig
Good results can be obtained by adding the above amine compound to a basic bath or a basic bath containing an amine compound and a sulfur-containing compound in the concentration range of /A, but if it is added too much, the black color becomes thinner and coverage is poor. Become.

Next, by adding zinc ions to the basic bath to which the amine compound and surfactant have been added, the degree of blackness can be further increased, producing a deep black color especially in high current areas. Also, since it is a ternary alloy, there are some difficulties in managing it, but it can be put into practical use.

It is safe to use carbon as the anode in this electroplating, but any metal anode that has been treated with insolubilization can be used.

Also, since it contains divalent tin, it is better to avoid air agitation, and it is better to select mechanical agitation, jet agitation, magnetic agitation, cathode rocker, etc.

Further, these electroplating methods can be applied not only in a stationary state but also in a rotating bath. Nickel plating is good for base plating, and it can be plated directly onto iron substrates, brass, etc., but the color tone will be lighter.

<Example 1> Dissolve 30 g/l of cohal sulfate and 5 g/l of tin sulfate, and dissolve 60 g/l of sodium gluconate. m Adjust pt+ to 7 to 9.5 with aqueous ammonia and use this as the basic bath.

Add the amine compound jetanolamine to this basic bath.
g/N, surfactant polyethylene oxide polypropylene oxide broth polymer (Kao soap, PP
150) was added, anode carbon, magnetic stirring, I A / d rd for 3 minutes at 30°C, and the Hull cell was plated with a glossy nickel i degree in a Hull cell bath, resulting in a black glossy coating. Some cobalt tin plating was obtained.

<Example 2> In the basic bath of Example 1, the amine compound monoethanolamine and epichlorohydrin were reacted at a ratio of 1:0.5M.
0% solution was added at 7 ml/1, surfactant PP150 was added at 0.1 g/g, and sulfur-containing compound 2,5-dimercapto/1,3.4-thiodiazole was added at 0.2 g/l. Hull cell plating was performed at 35° C. and LA/dm for 23 minutes. A darker black cobalt tin plating than in Example I was obtained, and the sulfur-containing compound 2.5-dimercapto.1.3.4
- No sulfur-based odor was generated by adding thiodiazole.

Comparative Example 1> Using sodium hydroxide instead of ammonia in the basic bath of Example 1, the amine compound jetanolamine was
When plating was performed by adding 0.5 g/l of PP150 as a surfactant, a black color was obtained in some areas, but the plating was very uneven. Therefore, better results can be obtained using ammonia than sodium hydroxide.

<Example 3> 3 g of quatrol, an amine compound, was added to the basic bath of Example 1.
/l, surfactant polyethisane oxide oleyl ether 0.5g/l, a-methionine 3g/12
was added. Cobalt tin plating with a deep black color was obtained, but it had a peculiar odor, and the odor became more intense as the plating progressed.

<Example 4> Adding 5 g/l of zinc sulfate to the composition of Example 1,
A/dm'' 3 minutes without stirring, a deep black plating was obtained, but the high current density areas were particularly black.

When the plating was performed while stirring, it became uniform.

Comparative Example 2> When the amine compound was excluded from the composition of Example 2 and plating was performed, black color was not obtained, and dark nickel-like color and brown burnt were produced.

<Effects of the Invention> The electroplating bath of the present invention does not contain harmful substances such as hexavalent chromium, so wastewater treatment is easy, and by adding a sulfur-containing alkylamine, no sulfur-based odor is generated. This increases safety during work.

Also, black Kohar Hl on bright nickel plating! By applying gold, an elegant cobalt deposited film is obtained, which has excellent corrosion resistance and discoloration resistance, and is suitable for products that require black color, such as electrical products and camera parts.

Claims (4)

[Claims] (1) The main component is a cobalt salt, a stannous salt, an alkali metal salt of gluconic acid or glucoheptonic acid, and the cobalt salt is 3 to 25 g/l as a metal, and the stannous salt is 0.1 to 25 g/l as a metal. An amine compound is added as an additive to a basic electroplating bath containing 30 to 150 g/l of an alkali metal salt of gluconic acid or glucoheptonic acid, and the pH of which is adjusted to 7.0 to 10.0 with aqueous ammonia. A black electroplating bath characterized by (2) The black electroplating bath according to claim 1, characterized in that a surfactant is added as an additive. (3) The black electroplating bath according to claim 1 or 2, characterized in that a sulfur-containing compound is added as an additive. (4) The black electroplating bath according to claim 1 or 2, characterized in that zinc ions are added as an additive.