TARNISH AND PROTECTION OF SILVER DEPOSIT——MECHANISM AND METHOD

摘要

The mechanism of tarnish caused by exposure to light and Na₂S solution treatment on silver-electroplated deposit and the antitarnish effects of various antitarnish agents have been investigated in this paper. The results showed that 1-phenyl-5-mercaptotetrazole （PMTA） has excellent antitarnish effect for UV light and H₂S tests.The studies of XPS and AES and UV absorption spectra showed that PMTA can absorb effectively UV light and form a dense surface film which can prevent effectively the reactions between silver deposit with corrosive media.Antitarnish surface film could be composed of a polynuclear coordination polymeric compound with structure unit approximate to [Ag₃（PMTA）]. according to the depth dependence of percent component （C%） and sputtering time.