Structure of High-temperature Oxidation Zones of Gold Alloys for Metal-Porcelain Bonding Containing Small Amounts of In and Sn

Changes in the morphology of the oxidation zone and the quantities of oxide for gold alloys containing two base metals (In and Sn) were investigated by exposing alloys at 1000°C for one h in air. The contents of In and Sn were varied in the range of from 0-1.5 wt%. In the range of from 1.5-0,35 wt% In (from 0-1.15 wt% Sn), In2 O3 was formed predominantly at the alloy surface. The electron probe x-ray micro-analyzer detected no uniform external oxidation zone. A mixture composed of In2O3 and SnO2 precipitated internally in the alloy matrix. An external oxidation zone composed of SnO2 was formed on the alloys containing over 1.2 wt% Sn, and no internal oxidation zone was observed.