Insights into structural evolution and corrosion resistance of amorphous passive film of Ti80 under different pH conditions

Ti80 alloy is coated with a dense passive film whose excellent corrosion resistance is crucial for marine engineering applications. This study investigated structure, properties, and evolution of the passive film upon Ti80 as a function of pH in simulated marine environments. Results indicated that the passive film is amorphous and thin (less than 10 nm in thickness), primarily composed of rutile-type connection of [TiO 6 ] octahedron and a high concentration of hydroxides and hydrates. Composition of the passive film influences its density and diffusion resistance. Besides, Ti80 exhibited two patterns with pH: an extreme value near neutral, attributed to the cathodic reaction regulating the repair process; and a monotonic change with pH, reflecting corrosion resistance of the film. Subsequent analysis revealed that carrier density decreased while diffusion resistance and film stability increased with pH. In addition, Cl⁻ accelerated film destruction in acidic environments, and corrosion resistance increased with pH. This study establishes a structure-performance correlation mechanism and refined the corrosion mechanism of Ti80 in marine environments.