JPH0510438B2 - - Google Patents

Description

[Detailed description of the invention]

[Objective] The present invention relates to electroplating of metal bodies, particularly gold, silver,
The present invention relates to a method for efficiently and economically reducing consumption due to pumping out precious metals in an electroplating line for plating precious metals such as palladium. [Prior art 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, and are used as electronic and electrical components due to their excellent corrosion resistance and electrical connectivity. It is used for such purposes. The metal body to be plated can be copper, brass, copper alloys such as phosphor bronze, iron, steel (stainless steel, etc.),
Iron alloys such as 42 alloy 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 the parts are coated with barrel plating or easy plating, but this method is difficult due to productivity and economic considerations. Increasingly, strips of metal are plated before being formed into individual parts, which are then formed into parts. When precious metal plating is performed on a metal body to be plated, the metal body plated in the precious metal plating tank is drained (in the case of continuous strips, drained with an air knife, etc.), and then subjected to the next treatment. Transported to tank. The consumption of precious metals contained in the plating liquid 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 avoided no matter how strong the liquid draining device, such as the air knife mentioned above, is used. isn't it. Keeping the pumping amount low as mentioned above is
This is an extremely important issue in achieving low-cost precious metal plating. A common way to deal with this problem is to install two or more stages of precious metal recovery tanks, such as washing tanks, to wash away the precious metals from the plated metal objects and recover them using various methods. . However, installing multiple recovery tanks in a plating device, especially in a continuous plating device, not only increases the installation space, but also requires separate processing equipment for electrolytic recovery and recovery of precious metals from the liquid in the recovery tank.
Recovery by ion exchange resin must be carried out. [Structure of the Invention] In view of this point, the present invention has carried out various studies in order to minimize the consumption of plating metals such as precious metals due to pumping and to perform efficient plating in metal electroplating equipment. As a result, an electrolyte solution tank (hereinafter referred to as a recovery electrolytic tank) that does not contain metal ions such as precious metals for plating is provided next to the electroplating tank for precious metals, and the plated metal bodies are collected in this recovery electrolytic tank. It has been discovered that by electrolyzing as a cathode, losses due to pumping out of 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 removed. Transferred to a recovery electrolyzer. By further electrolyzing the plated metal body using the plated metal body as a cathode, the plated metal remaining in the pumped-out plating solution is deposited on the plated metal body. 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. By pumping the plating solution from the electroplating solution to the recovery electrolytic tank, the concentration of the electrolyte solution in the recovery electrolytic tank,
Since the components, pH value, etc. gradually change, it is desirable that the electrolytic solution for electroplating and the electrolytic solution in the recovery electrolytic tank be of the same system, and the electrolytic solution should be selected appropriately to ensure effective plating. Ru. Further, when the plating metal 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 a plating metal" means that the plating metal that inevitably enters the recovery electrolytic tank by pumping out the plating solution is excluded, and of course, the electrolyte solution that does not contain a plating metal is excluded. The electrolyte solution of the recovery electrolytic cell in which the plating metal contained in the plating solution is mixed is included in the above-mentioned "electrolyte solution not containing the plating metal" of the present invention. When electroplating metal strips continuously, even if an air knife is used as described above, pumping out of the plating solution cannot be sufficiently prevented. Preventing losses is extremely effective. Generally, 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 methods are single-sided, stripe, or spot plating. It's summery. In the case of partial plating, additional equipment for partial plating is required, so it is appropriate that the recovery electrolytic cell 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.

【table】

[Table] As shown above, 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 the electrolytic solution has the same composition as the plating solution. 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 thickness of 0.2 mm and a width of 60 mm was continuously plated with gold stripes. Plating width is 5mm
There is only one stripe. At the outlet of the gold plating tank, the gold plating solution is removed from the strip using an air knife, and then the strip is transported to a recovery tank. At that time, Table 1 shows the changes in the gold concentration in the recovery tank for the case where the gold was immersed in pure water (comparative example) and the case where it was electrolytically recovered (example of the present invention). The plating conditions are as shown below. Plating conditions: (1) Threading speed 10m/min (2) Gold plating solution Potassium gold cyanide 12g/ Potassium citrate 125g/ Potassium antimonyl tartrate 1g/ EDTA cobalt salt 3g/ (3) Electrolyte solution for electrolytic recovery Potassium citrate 125g/ Potassium antimonyl tartrate 1g/ EDTA cobalt salt 3g/ (4) Recovery tank liquid volume (both pure water immersion and electrolytic recovery) (5) Electrolytic recovery current density 0.5A/dm ²

[Table] As shown in Table 1, it was confirmed that gold was electrolytically recovered in the electrolytic recovery tank and that the gold 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), and by combining one stage of electrolytic recovery tank and one stage of pure water immersion type recovery tank. It was confirmed that the two-stage case was almost equivalent.

Claims (1)

[Scope of Claims] 1. When electroplating a metal body, the plated metal body is electrolytically treated as a cathode in an electrolyte solution of a recovery electrolytic tank to which no post-plating metal is added. An electric device characterized in that the plating metal remaining in the plating liquid pumped out along with the plating metal body when the plating metal body is transferred from the plating tank to the recovery tank is deposited on the plating metal body. How to attach. 2. The electroplating method according to claim 1, wherein electrolysis is carried out in an electrolyte solution of the same type as the electrolyte solution for electroplating, to which no plating metal is added. 3. The electroplating method according to claim 1 or 2, in which a metal strip is continuously electroplated.