A method of inhibiting corrosion of copper - and copper alloy surfaces

摘要

A process of treating a surface of Cu or of a Cu alloy to inhibit tarnishing or corrosion thereof comprises contacting the surface with a mixture (e.g. a solution or dispersion) of a water-soluble ferricyanide with at least one benzotriazole compound. The term benzotriazole compound includes benzotriazole itself and Cu-protecting derivatives thereof such as 5-alkylbenzotriazole or a 5-acylaminobenzotriazole. Examples of such compounds are given in Specifications 1,065,995 and 1,069,392. The ferricyanide may be ammonium or alkali metal ferricyanide or a mixture of two or more thereof. Before contacting with the mixture, the Cu may be contacted with a solution of chromate or dichromate or mixture of two or more thereof or with a solution of soap as described in Specification 1,065,997. Contact with the mixture containing a benzotriazole compound may be for 0.5 to 30 minutes at a temperature from 10 DEG C. to the boiling point of the mixture. In the Example, Cu foil is cleaned in acid solution, washed, immersed for 2 minutes in an aqueous solution containing 0.1% by weight of benzotriazole and 0.05% by weight of potassium ferricyanide at 65 DEG C., washed, dried and then tested for tarnish resistance with H2S.