Pure iridium and iridium-rhodium alloys ingots were first oxidized in air at 1550℃ for 10 h, and their weight loss and microstructures were investigated. Weight loss experiments showed that the weight loss rate of iridium and iridium-rhodium alloys decreases with the increase of rhodium content. The weight loss of iridium-rhodium alloys with 30%~50% Rh is only half that of pure iridium. Grain boundary observations showed that grain boundary oxidation corrosion occurred both in the iridium and iridium-rhodiu...