AN ANTITARNISH FILM ON BRASS

1-Phenyl-5-mercaptotertrazole (PMTA) was found to be more effective th an chromate and other organic agents for protecting brass from tarnish ing. A 5 min passivation treatment in 1.2 g dm(-3) of PMTA solution at 30 degrees C formed a protective film on Cu2O and ZnO. Based on X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES ) determinations, the film formed had a composition of 47.2% C, 20.6% Cu, 6.5% Zn, 12.7% N, 9.1% S and 3.9% O. It was deduced from differenc es in binding energies of N and S before and after film formation that N and S in the PMTA structure were coordinated with Cu+ and Zn2+ in t he film. (C) 1998 Elsevier Science S.A.