Colored conversion films of Mo-S-Cu cluster compounds on a copper surface

Conversion films of Mo-S-Cu cluster compounds with a metallic luster of various colors have been obtained on a copper surface; their colors have been changed by heat treatment. Accelerated corrosion and tarnish tests indicate that PMTA passivation enhances the anticorrosive ability of the conversion films and the stability of their colors. FT-IR, XPS and AES determinations were made to investigate these conversion films before and after being heated. The results show that the colors of the heated and unheated films are probably caused by Mo-S-Cu bonds and a statistical distribution and overlapping of various molecular layers inasmuch as the films are complicated multicomponent and multilayer systems. The disparity of colors before and after heating treatment is caused by change of composition and structure of the films.