Insights into high temperature oxidation of Al2O3-forming Ti3AlC2

► Insights into high temperature oxidation of Al2O3-forming Ti3AlC2 are made. ► The protective Al2O3 scale results from selective oxidation of Al. ► Oxygen grain boundary diffusion predominates for scale growth. ► Al2O3 grains grow with time, yielding a sub-parabolic oxidation rate. ► Al diffuses in a fast manner, accounting for the absence of Al-depletion zone.