On the oxidation mechanism of Ni–Pt alloys at high temperatures

The oxidation mechanism of Ni–Pt alloys has been studied as a function of alloy composition, oxygen pressure and temperature. It has been found that the oxidation rate of all the alloys follows the parabolic rate law, being thus diffusion controlled. In agreement with Wagner’s theory, the slowest step of the overall oxidation rate of alloys with higher nickel content (⩾40 at.%) is determined by the outward diffusion of nickel cations in the growing NiO scale. On the other hand, the oxidation rate of alloys with a lower nickel content (<40 at.%) is governed by the solid state diffusion in the metallic phase.

► Kinetics of Ni–Pt alloys’ oxidation.
► The influence of composition of alloys on their oxidation mechanism.
► Diffusion of Ni in NiO determines the oxidation rate of alloys with high Ni content.
► Diffusion of Ni and Pt in the alloys with low Ni content determines the oxidation rate.
► Disagreement between experimental data and theory results from internal oxidation.