Highly dense passivation enhanced corrosion resistance of Ti2AlC MAX phase coating in 3.5 wt.% NaCl solution

Abstract

This study aimed to investigate the dependence of electrochemical behavior upon the microstructural evolution of Ti2AlC MAX phase coating in 3.5 wt.% NaCl solution. The results showed that high-purity Ti2AlC coating with unique equiaxed nanocrystals exhibited remarkably higher impedance and lower current densities compared to those of uncoated Ti-6Al-4V substrate, which was attributed to the formed highly dense and continuously amorphous Al2O3 passive film on the coating surface. According to the combined DFT calculations, both the large diffusivity of Al atoms and the robust stability of Ti2AlxC with Al vacancies exceeding 50% contributed to the unusual achievement of electrochemical passivation characteristics, enabling the significant enhancement of anti-corrosion capability for Ti2AlC coating.