ABSTRACT
Many objects of cultural heritage constituted of bulk, plated silver or alloys are often displayed in museum show-cases or kept in depositories. The silverworks tarnish with time by reactions with atmospheric pollutant elements, namely sulfides forming silver sulfide. The blackish films thus formed make these artifacts inappropriate to display and have to be dealt with. Tarnish can be removed with a silver polish, by a chemical dip, an electrochemical reduction method or galvanic coupling with aluminum. Several methods have been developed to reduce silver tarnish such as silver alloying, surface treatment and coating. The protection system employed, has to follow the Venice Charter, to be removable and not to change the aesthetics of the object to be protected. In this study, silver alloys have been tested for corrosion under accelerated atmospheric corrosion conditions. A system of hexadecane-thiol [HOT] has been tried on silver coupons. An acrylic copolymer has also been used as the organic vehicle for dispersed nano-pigment of aluminum oxide. Several percentages of pigments have been tried to check on the system capabilities, without altering the visual effects of the surface. The different coating systems have been prepared and either brushed on the surface of the silver coupons or the silver coupons were immersed in the coating system. Alternate immersion testing in sulfide solution has been tried on the coupons. Electrochemical testing, visual observations and gloss measurements showed that the coating with 2% nano-AI2O3 and the hexadecane-thiol exhibit better protective properties than the plain acrylic