Internal and external oxidation of Pt(Al) solid solution at elevated temperatures

High temperature oxidation of Pr(AI) solid solution and Pt(AI) with Pt3Al w as investigated in order to prepare a Pt wire with an external Al2O3 dlm fo r a hot-wire technique to measure thermal conductivities of fused metals. A r temperatures from 1373 to 1673 K in air, Pt-4.6 mol % Al (solid solution) indicated internal oxidation. Continuous Al2O3 scales developed on Pt-9.4 mol % Al (solid solution) and Pt-13.1 mol lo (the two-phase alloy). Externa l scales formed on those alloys after high temperature oxidation under low oxygen pressure of Ar-10%H-2-0.6%H2O gas mixture. The oxidation rate increa sed with increasing Al content and oxygen partial pressure. The Al concentr ation at the transition from internal to external oxidation was determined by using oxygen permeability through Pt-Al alloys calculated from internal oxidation kinetics. (C) 2000 The Electrochemical Society. S0013-4651(99)01- 059-9. All rights reserved.