Effects of β‐Stabilizing Elements on the Corrosion Resistance of Ti‐6.5Al Alloys in Hydrochloric Acid: DFT Calculations and Experimental Validation

ABSTRACT To evaluate the effects of various β‐stabilizing elements (AEs: Nb, Mo, Cr, V, Fe) on the corrosion resistance of Ti‐6.5Al alloy in hydrochloric acid, this work employs density functional theory (DFT) calculations to investigate the interactions between HCl molecules and TiO 2 passive film surfaces doped with different AEs, with experimental validation via electrochemical measurements and immersion tests. Nb doping decreases the absolute adsorption energy from 0.65 to 0.63 eV and broadens the band gap from 3.52 to 3.63 eV, corresponding to reduced Cl − adsorption and surface reactivity. Mo, Cr, V, and Fe increase the adsorption energy to 0.71, 1.55, 1.69, and 1.88 eV, respectively, and narrow the band gap, associated with enhanced Cl − adsorption and surface reactivity. Electrochemical and immersion tests show that 1 at.% Nb addition increases the corrosion potential and film resistance, and decreases the corrosion rate and corrosion current density, whereas Mo and Fe additions exhibit the opposite effects. These observations correlate the type of alloying element with Cl − adsorption energy and passive film stability.