Effect of carbon coatings on gold dissolution in the presence of sulphide and lead

SEM analysis revealed much less erosion of gold occurring with the addition of sulphide. The gold surface showed highly corroded spots scattered across relatively less corroded areas during leaching with the addition of lead, while the gold surface was smooth after leaching with a carbon coating. An XPS investigation indicated the formation of AuSx at the gold surface with the addition of sulphide. Metallic lead or AuPb alloys and lead hydroxide were detected at the gold surface after leaching with the addition of lead. The carbon coating hindered the diffusion of lead to the gold surface and hence reduced the beneficial effect of lead on gold dissolution.