Is gold always chemically passive?: Study and comparison of the epoxy-amine/metals interphases

When epoxy-amine liquid mixtures are applied onto metallic substrates (such as Al, Ti, Sn, Zn, Fe, Cr, Cu, Ag, Ni, and Au), concomitant amine chemisorption and metallic surface dissolution occur, leading to organo-metallic complex formation. The interphase formation was studied, using two different amines as hardener (IsoPhoroneDiAmine and DiEthyleneTriAmine). If the complex concentration within the liquid amine or epoxy-amine prepolymer was higher than its solubility limit, the complexes will crystallize. Sharp needle-like crystals were only observed with metal-IPDA organo-metallic complexes. A lot of metals are widely used as reactive substrates with gold as a reference, which is considered chemically inert. It is misleading, since it will be shown in this article that gold reacts with amine, just as the other metals.