Selective dissolution of AuCu and AuAg alloys in vitro and in vivo

AuCu and AuAg alloys (30 at. % Au) have been immersed in aqueous solutions of chloride and sulphide with additions of protein (mucin). The surfaces of the alloys were subsequently analysed by means of ESCA and compared with previous and similar tests without addition of mucin. No noticeable effect of the mucin addition was observed on the surface composition of the alloys after exposure to the various solutions. Cu in contrast to Ag was found to be selectively dissolved from the 2 or 3 uppermost atomic layers in chloride as well as sulphide solutions (pS greater than 4), both with and without additions of mucin, leaving behind a surface enriched from 10 to 25 at. % in Au. Testing of the same alloys in vivo for 8 d revealed the same tendencies to selective dissolution of Cu. The AuAg alloy was tarnished in the sulphide solutions and in vivo.