This study investigates the electrochemical corrosion behavior and surface passive mechanism of Ti 3 AlC 2 MAX phase coating to advance their application in marine environments. Ti 3 AlC 2 coating was deposited on a Ti-6Al-4V substrate using high-power impulse magnetron sputtering followed by annealing, and its corrosion performance was systematically evaluated in 3.5 wt.% NaCl solution. The results revealed exceptional corrosion resistance with a current density of 5.74 × 10 -10 A∙cm -2 , which is two orders of magnitude lower than that of the substrate, along with higher impedance modulus, demonstrating superior corrosion resistance. Microscopic characterization confirmed the formation of a continuous, dense, amorphous Al 2 O 3 passive film with an average thickness of 4.07 nm. The lower vacancy formation energy of Al atoms, as determined by DFT calculations, underpins the preferential diffusion of Al in Ti 3 AlC 2 and accounts for the formation of a single Al 2 O 3 passivation layer at the microscopic scale. The film growth follows a high-field model, with thickness increasing logarithmically over time, governed by inward oxygen ion migration. Critically, the relatively low aluminum content in Ti 3 AlC 2 leads to form an amorphous diffusion transition zone beneath the passive film. This diffusion zone mitigates structural destabilization caused by aluminum depletion, preventing film delamination and enhancing long-term protection. The study elucidates the selective formation and growth mechanisms of the passive film on Ti 3 AlC 2 MAX phase coating, providing a theoretical basis for their use in aggressive corrosive environments.
Xu et al. (Sun,) studied this question.
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