POST-TREATMENT OF METALLIC PLATING

摘要

PURPOSE:To reduce the concn. of sexivalent Cr in a soln. for sealing the pinholes in metallic plating by adding a surfactant to the soln. contg. sexivalent Cr and an alkali metallic salt. CONSTITUTION:The pinholes in thin gold or silver plating for ornamentation are sealed by forming Cr oxide films in the pinholes to prevent the tarnish are corrosion of the plating. This post-treatment is carried out by cathodically electrolyzing the plating in a soln. contg. 10-900mg/l sexivalent Cr and 0.01-10g/l in total of an alkali metallic hydroxide or carbonate and a surfactant. Though the concn. of sexivalent Cr in the treating soln. is extremely low, the effect of the soln. is comparable with that of a high concn. bath. The surfactant does not necessarily produce a significant effect.