Reduction of silver tarnishing and protection against subsequent corrosion

The kinetics of tarnishing formation was examined on a polished silver dipped in a 10 mM Na2S. The recovery of an initial bright surface was then obtained by cathodic reduction of the tarnish layer in a 5% sesqui-carbonate solution. Two protection methods to prevent a further formation of a dark deposit were tested: an electrodeposited poly(amino-triazole) film and the surface treatment in hexadecane-thiol. The protection by poly(amino-triazole) is not reliable for all nuances of silver. In contrast, the film formed with hexadecane-thiol showed satisfactory properties. The formations of tarnish and protective films were examined by electrochemical methods, the reflectance measurements, and the quartz crystal microbalance. (C) 2004 Elsevier Ltd. All rights reserved.