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.