KR101058087B1 - Cobalt-Tin Alloy Plating Solution - Google Patents

Abstract

The present invention relates to a cobalt-tin alloy plating, and to a plating solution that improves the instability of the plating solution and obtains a plating layer having a high corrosion resistance of a constant alloy ratio over a long period of time. L, the second tin fluoride 10 ~ 15g / L, ammonium bifluoride 80 ~ 100g / L, ammonium chloride 100 ~ 120g / L, the varnish 0.5g / L, the temperature of the plating solution is 60 ℃ ± 2 ℃, The pH of the plating solution is characterized in that the plating for 90 ~ 120 seconds under the condition of 1.0 ~ 1.5.

Cobalt-tin alloy plating, cobalt chloride, tin fluoride, ammonium chloride, brightener

Description

Cobalt-Tin alloy plating solution

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to cobalt-tin alloy plating, and relates to a plating solution composition which improves the instability of the plating solution and obtains a plating layer having a high corrosion resistance of a constant alloy ratio over a long period of time.

Tungsten-cobalt alloy plating or cobalt-tin plating has been developed to replace the high corrosion resistance, wear resistance, and brilliant white plating layer of chromium plating.

However, in any plating, the stability of the plating solution was not maintained for a long time, and the strength and corrosion resistance of the alloy layer were inferior to chromium plating, and thus, it was not widely used in industrial fields.

Cobalt-tin plating has been developed as a replacement for white chromium plating, and depending on the metal alloy ratio, it can give a variety of colors ranging from blue-white to yellow-white or blue-black to dark brown.

However, most of the cobalt-tin alloy plating work in the alloy ratio of blue-white similar to white chromium plating, and the alloy ratio of cobalt and tin is maintained at about 20:80.

Chrome plating, which has been widely used in industrial sites, has been applied to trivalent chromium plating due to the toxic hexavalent chromium.However, the plating layer is unstable and the plating property is not smooth. Many defects that are not plated occur.

For this reason, plating of cobalt-tin alloy has been developed as a substitute for chromium plating in barrel plating in which a large amount of small products are put into the barrel.

Conventional cobalt-tin plating is known as a pyrolic acid bath based on a weak alkali bath, a cobalt-tin alloy plating method of an acid-based stannate bath and an acid solution.

Pyroic acid bath is a weak alkali of about PH8.0 ~ 9.5 with pyrochlorate as the conducting salt and cobalt chloride 15 ~ 50g / L and ditin tin 15 ~ 50g / L as additives. To give luster.

In cobalt-tin plating, a brightener may use a small amount of a surfactant, but the gloss may be affected by the alloy ratio and the concentration ratio of each mixed chemical due to the gloss effect of the alloy itself.

Pyrophosphate plating has the advantage that the color is similar to chromium plating and relatively stable color management is possible, but divalent tin is oxidized in the plating bath and turns into tetravalent tin and is naturally consumed.

In addition, since pyrroline salts do not have stability in contact with chlorides such as cobalt chloride, there is a problem that precipitates occur in the plating solution.

Therefore, this deposit has to be removed by continuous filtration, and also has a weakness in that excess pyrophosphate, cobalt chloride, and tin chloride are consumed in excess to compensate for the conductive salt consumed by the precipitation.

Another cobalt-tin alloy plating stannate bath is based on an aminocarboxylic acid as the conducting salt and is based on cobalt chloride 5-15 g / L and sodium phosphate 15-40 g / L, with an alkaline pH of 12-13. It is an alloy plating solution with high stability of tin because tetravalent tin salt is used for alloy plating.

The stannate bath is less affected by metal impurities than pyroic acid bath, but when organic impurities accumulate, the electrodeposition and plating properties are extremely bad. Tin is oxidized and insoluble when PH is out of a certain range because it is sensitive to PH retention. It will form a precipitate.

Pyroic acid baths are vulnerable to metal impurities and stannate baths are vulnerable to organic impurities, which makes it very difficult to obtain stable alloy plating in any case.

Therefore, in order to solve the above problems, cobalt-tin alloy plating of acid solution insensitive to impurities has emerged as an alternative to weak alkali or alkali alloy plating.

Cobalt-tin alloy plating of acid solution is made of cobalt chloride and tin chloride alloy, or cobalt-tin alloy plating of cobalt chloride and tin fluoride alloy is 15 ~ 50g / L cobalt chloride and 15 ~ 50g tin chloride, respectively. / L as a metal additive, ammonium chloride 50 ~ 100g / L, cobalt chloride 100 ~ 300g / L, tin fluoride 15 ~ 50g / L, ammonium chloride or ammonium bifluoride 50 ~ 100g / L If it is.

The acid solution is relatively stable and the color ratio is not large because the alloy ratio is stable.

However, since the electrodeposition property is not good compared with a pyroic acid bath or a stannate bath, an unplated part tends to generate | occur | produce, and also there exists a tendency for the precipitation by oxidation of tin to generate | occur | produce.

In addition, when the concentration of cobalt is not high, the precipitation ratio of cobalt is lowered, so that plating is not uniform and the color of the alloy tends to go to a black ground.

The present invention prevents the precipitation of the cobalt-tin alloy plating solution to prevent excessive consumption of conductive salts, cobalt chloride, tin chloride, and the like, and enables the plating solution to maintain stable alloy plating against impurities. It is to provide a method for improving the electrodeposition property so that the unplated portion does not occur to make the plating uniform.

The present invention first increases the amount of cobalt chloride, which is a cobalt additive in the plating bath, to 400-600 g / L and lowers the pH of the alloy plating bath to 1.0-1.5, thereby reducing the formation of complex salts.

In addition, since the concentration ratio of the metal additive of the alloy plating bath at low PH is not proportional to the alloy deposition ratio, the tin concentration is very low to 10 to 15 g / L, and the second tin fluoride which is more stable in the acidic alloying solution is used.

In addition, ammonium bifluoride is mixed with ammonium chloride to stabilize the solution and used as a conductive salt, and a small amount of thiourea (CH₄N₂S) is added for gloss.

The work is set at 60 ° C and the current is set at 0.5 to 0.8 A / dm² and the time is set to 90 sec.

The present invention is environmentally friendly because it does not contain environmentally harmful substances in the working process and the plating solution, so it can be applied to the substitution of chromium plating and barrel plating, and can suppress the occurrence of deposits in the plating bath, so that the conductive salt, cobalt chloride, tin chloride This can be prevented from being consumed more than necessary, it is possible to improve the electrodeposition properties and to improve the plating quality such that the unplated portion does not occur.

Hereinafter, a preferred embodiment of the present invention will be described in detail.

The present invention relates to a stable cobalt-tin alloy plating solution which maintains a constant ratio of the alloy at all times, prevents precipitation due to tin salting and is less affected by impurities, and also provides a method of making the alloy plating solution available for a long time. To provide.

First, the amount of cobalt chloride, cobalt additive, is very high to 400 to 600 g / L and the pH of the alloy plating bath is lowered to about 1.0 to 1.5, thereby reducing the formation of complex salts.

In addition, it is noted that the concentration ratio of the metal additives of the alloy plating bath is not proportional to the alloy deposition ratio at low pH, and the tin concentration is very low to 10 to 15 g / L, and the second tin fluoride is more stable in the acid alloy solution.

To stabilize the solution, ammonium bifluoride is mixed with ammonium chloride and used as a conducting salt, and a small amount of thiourea, a gloss agent, is added for gloss.

The work was set at a temperature of 60 ° C., with a low current of 0.5-0.8 A / dm² and a time of 90 seconds.

Alloy plating under these conditions yields an excellent cobalt-tin light blue-white alloy layer of 0.1 탆 / min plating thickness.

This alloy layer has excellent adhesion of plating because it works near PH1.0 which is strong acid.

Moreover, since glossiness is good, the plating layer of the 0.2-0.5 micrometer high glossiness layer can be obtained, without adding a separate gloss agent.

Since it works with high adhesion in the strong acid state, the strength of the alloy layer is strong, and it has an excellent function in maintaining wear resistance and corrosion resistance.

In this case, the alloy ratio of cobalt and tin is maintained at a ratio of 85 to 90: 10 to 15.

To summarize this alloy condition briefly,

Cobalt Chloride 400 ~ 600g / L

Tin Difluoride 10-15g / L

Ammonium Bifluoride 80 ~ 100g / L

Ammonium Chloride 100 ~ 120g / L

Thiourea (CH₄N₂S) 0.5g / L

Temperature 60 ℃ ± 2 ℃

PH 1.0 ~ 1.5

90 ~ 120 sec

The alloy layer of 0.2 micrometer cobalt: tin = 87: 13 was obtained on condition of.

The present invention can be applied both to the metal forming the brilliant white cobalt-tin alloy layer, to the intermediate layer or to the final layer plating of all platings of nonmetals.

Claims (5)

In a plating solution for forming a cobalt-tin alloy layer containing cobalt chloride and tin fluoride as a metal additive, Cobalt Chloride 400 ~ 600g / L Tin Difluoride 10-15g / L Ammonium Bifluoride 80 ~ 100g / L Ammonium Chloride 100 ~ 120g / L A cobalt-tin alloy plating solution characterized by mixing in the range of 0.5g / L of a brightener. The cobalt-tin alloy plating solution according to claim 1, wherein the plating solution has a temperature of 60 ° C ± 2 ° C. The cobalt-tin alloy plating solution according to claim 1, wherein the plating solution has a pH of 1.0 to 1.5. The cobalt-tin alloy plating solution according to claim 1, wherein the plating time of the plating solution is 90 to 120 sec. The cobalt-tin alloy plating solution according to claim 1, wherein the brightening agent is thiourea.