JPS6244591A - Electroplating method - Google Patents

Abstract

PURPOSE:To reduce the loss of a metal for plating such as a noble metal by the drag-out of a plating soln. and to save recovering expenses by electrolyzing an electroplated metallic body as the cathode in an electrolyte soln. not contg. a metal for plating. CONSTITUTION:A metallic body electroplated with a noble metal is pulled up from a plating soln. and conveyed to a recovering tank, where the metallic body is electrolyzed as the cathode in an electrolyte soln. not contg. a metal for plating. By this electrolysis, metallic ions remaining in the plating soln. dragged out together with the metallic body is deposited on the metallic body, so plating is carried out in consideration of the thickness of a layer formed by said deposition.

Description

[Detailed Description of the Invention] [Objective] The present invention is directed to electroplating of metal bodies, particularly in an electroplating line for plating precious metals such as gold, silver, palladium, etc.
The present invention relates to a method for efficiently and economically reducing consumption due to pumping of precious metals.

[Conventional technology and problems] In general, products plated with precious metals such as gold, silver, and palladium are used as decorative items because of their beautiful appearance, or are used as electronic and electrical components due to their excellent corrosion resistance and electrical connectivity. It is used for the following purposes.

As the metal body to be plated, copper, brass, copper alloys such as phosphor bronze, iron, steel (stainless steel etc.), iron alloys such as 42 alloy, etc. are used.

As a plating method, there is a so-called post-plating method in which metal strips are formed into individual parts in advance and then these parts are coated with barrel plating or rack plating, but from the viewpoint of productivity and economy, forming into individual parts is possible. Increasingly, metal strips are first plated and then formed into parts.

When precious metal plating is performed on a metal object to be plated, the metal object plated in the precious metal plating tank is drained (in the case of continuous strips, the liquid is drained with an air knife, etc.), and then transported to the next processing tank. Ru.

The consumption of precious metals contained in the plating solution that adheres to the metal objects to be plated and taken out of the plating tank, that is, the consumption of precious metals due to pumping out, cannot be achieved in just 1 minute, no matter how strong the liquid draining device, such as the air knife mentioned above, is. do not have.

Keeping the pumping amount low as described above is a very important issue in performing Rfi metal plating at low cost.

A common method for dealing with such problems is to install two or more stages of precious metal recovery tanks, such as washing tanks, to wash away the precious metal bones from the plated metal body and recover them using various methods.

However, installing multiple recovery tanks within a plating system, especially a continuous plating system, not only takes up a lot of installation space, but also requires additional processing equipment to perform electrolytic recovery or ion exchange in order to recover precious metals from the liquid in the recovery tank. Recovery with resin must be carried out.

[Structure of the Invention] In view of this point, the present invention has been made as a result of various studies to minimize the consumption of plating metals such as precious metals due to pumping and to enable efficient plating in metal electroplating equipment. Following the precious metal electroplating tank, an electrolyte solution tank (hereinafter referred to as a recovery electrolytic tank) that does not contain metal ions such as the precious metal for plating is provided, and electrolysis is performed in this recovery electrolytic tank with the wave-plated metal body as a cathode. It has been discovered that the loss caused by pumping out plated metals such as precious metals can be reduced, and recovery equipment can be significantly simplified and recovery costs can be reduced.

[Detailed Description of the Invention] When the electroplated material is transferred from the plating tank to the recovery electrolytic tank, the plating solution is simultaneously pumped out, and the plating metals such as precious metals contained in the plating solution are transferred into the recovery electrolytic tank. will be moved to By further electrolyzing the metal body to be plated using the metal body as a cathode, the plating metal remaining in the pumped-out plating solution is deposited on the metal body to be plated.

The thickness of the plating layer is determined by taking this precipitation into account and determining the overall thickness of the plating layer.

Therefore, the loss of plating metal caused by pumping out the plating solution as described above is significantly reduced.

As the plating solution is pumped from the electroplating solution to the recovery electrolytic tank, the concentration, components, PH value, etc. of the electrolyte solution in the recovery electrolytic tank gradually change. It is desirable that they be of the same type, and the electrolytic solution is appropriately selected so that plating can be performed effectively. Furthermore, when the plating gold J01 ion concentration of the plating solution in the recovery electrolytic cell of the same system becomes high, it can also be used as a replenisher for the plating solution.

In the present invention, "an electrolyte solution that does not contain plating metal" refers to the plating metal that inevitably enters the recovery electrolytic tank when the plating solution is pumped out, and excludes the plating metal that is naturally included in the plating solution when the plating solution is pumped out. Regarding the electrolyte solution in the recovery electrolytic tank in which plated metal is mixed, the above-mentioned "electrolyte solution that does not contain plated metal" of the present invention
It is included in.

When continuously electroplating metal strips, even if an air knife is used as described above, pumping out of the plating solution cannot be sufficiently prevented, so the recovery electrolytic tank of the present invention is provided to prevent loss of the plating solution. Prevention is extremely effective.

In addition, in general, when plating precious metals, it is expensive, so it is rather rare that the entire surface of the metal strip is plated, and the main plating method is partial plating, such as single-sided, stripe, or spot plating. ing. In the case of partial plating, since additional equipment for partial plating is required, it is appropriate that the recovery electrolytic tank has the same structure as the partial plating tank.

Examples of the electrolytic solution for plating and the electrolytic solution for improving the plating yield using the electrolytic recovery tank of the present invention are as follows.

Electrolytic solution for electrolytic recovery for plating Electrolytic solution (1) Silver plating silver cyanide 80-130 g / Q Potassium cyanide 90-140 g / Q 40-
80g/El charcoal ajj 'J uA 40-
113g/Q30-50g/Q Potassium Hydroxide 1120
~'IOg/Q (2) Gold-plated gold potassium cyanide l~1.2gIQ potassium cyanide 10~40g/Q 1.0~40g/Q Disodium phosphate 10~40g, l 10~40
gIQ (3) Gold, silver alloy plating Potassium gold cyanide 6-48g/ff Potassium silver cyanide 0.1-25g/Q Potassium cyanide 1110
~200g/QIO~200g/Q Titanium compound 0.05~5gIQ0.05~5g/Q Selenium compound 3g/Q or more 3g/Q (4) Platinum plating Chloroplatinic acid 2~6gIQ Ammonium phosphate 15~ 25g/Q15~25g
/Q Sodium phosphate 80~120g/lio~
120 g/Q (5) Palladium plated palladium chloride 2-5 g/Q Sodium phosphate dibasic 80-120 g/Q80-12
0g/Q diammonium phosphate 15-25g/Q15
~25gIQ benzoic acid 2~: 1g/1
22~3g/Q In this way, the electrolytic solution for electrolytic recovery basically has the same composition as the plating solution except that no plating metal ions such as gold or silver are added, and it is It goes without saying that the present invention can be applied to other cases as well.

The effects of the present invention will be specifically illustrated below using Examples.

[Examples and Comparative Examples] A phosphor bronze strip having a plate thickness of 0.2 nwn and a plate width of GOntn was continuously plated with gold plate 1 to live. Plating width is 5■
There is only one live performance. The strips are from the gold plating tank [■
After the gold plating solution is drained off using an air knife, it is transported to a collection box. At that time, Table 1 shows the changes in the total concentration in the recovery tank for the case of immersion treatment in pure water in the recovery tank (comparative example) and the case of electrolytic recovery (example of the present invention).

In addition, the plating conditions are as shown below.

Plating conditions: (1) Threading speed 10m/m1n (2) Gold plating solution Potassium gold cyanide 12g/Q Potassium citrate 125g/Q Potassium antimonyl tartrate 1g/Q EDTA Kobal 1-salt 3g/Q (3) Electrolyte for electrolyte recovery Potassium citrate 125g/Q Potassium antimonyl tartrate 1g/Q E L) T A ] Pal h Jlj, 3
g / Q (4) Recovery tank liquid volume 50Q (for both pure water TL immersion and electrolytic recovery) (5) Electrolytic recovery current density 0.5 A/dm2 The figures in Table 1 in the margin below are the total concentration of the recovered liquid (g/Q) As shown in Table 1 showing X′l! It was confirmed that gold was electrolytically recovered in the decomposition and recovery tank, and that the total concentration did not exceed a certain value.

Furthermore, as a result, the loss caused by pumping out gold can be reduced by installing three stages of pure water immersion type recovery tanks (batch type countercurrent washing tank).
It was confirmed that the results were almost equivalent to a case where one stage of electrolytic recovery tank and one stage of pure water immersion type recovery tank were combined to form two stages.

Claims (3)

[Claims] (1) An electroplating method for electroplating a metal body, which comprises electrolyzing the metal body to be plated as a cathode in an electrolyte solution that does not contain a plating metal after electroplating. (2) The electroplating method according to claim 1, wherein electrolysis is carried out in an electrolytic solution of the same type as the electrolytic solution for electroplating, which does not contain a plating metal. (3) The electroplating method according to claim 1 or 2, wherein a metal strip is continuously electroplated.