非シアン銀めっき浴の可能性に関する研究

概要

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Silver deposits formed on copper substrates by replacement reactions show poor adhesion, and a silver film plated on such a deposit dose not adhere. Silver ion makes a highly stable complex with cyanide ion, so that in a silvercyanide solution, the activity of silver ion is very small. This is one of the reasons for the universal use of cyanide baths in the industrial silver plating.However, consideration of the difference between the values of the stability constants for the silver-iodide complex and for the copper-iodide complex suggest that the rate of replacement deposition of silver on the copper substrate in silver-potassium iodide solutions, might be comparatively low. To confirm this, the rate of replacement deposition of silver in a silver-potassium iodide solution (AgNO3 0.10mol/L, KI 2.00mol/L) and in a strike silver plating bath (AgCN 0.028mol/L, KCN 1.15mol/L) was estimated from the current density corresponding to the point of intersection of the anodic and the cathodic polarization curves. These estimated values were almost the same, and it is suggested that the silver-potassium iodide solution is not only a cyanide free silver plating bath capable of employing a copper substrate but a silver plating bath which requires no strike plating.