The structure of oxide formed by high-temperature oxidation of commercial gold alloys for porcelain-metal bonding.

For gold alloys containing only In as a base metal, an external In2O3 layer forms uniformly on the alloy surface. However, when the alloy contains Sn and In, no external oxide layer can be detected by electron probe micro-analysis, and oxide particles composed of In2O3 and SnO2 precipitate in the alloy. For alloys containing Ni, in addition to In and Sn, the external oxide is composed of NiO; there is little development of internal oxide. For alloys containing Fe and Sn, an oxide layer of only Fe2O3 forms on the alloy surface, and the internal oxidation zone shows a band-like structure containing SnO2 and a small amount of Fe2O3.