Electrochemical behavior of Ti–6Al–4V alloy in Hank’s solution subjected to deep cryogenic treatment

The effect of deep cryogenic treatment (DCT) on the electrochemical behavior of Ti–6Al–4V alloy in Hank’s solution was experimentally investigated in the present work. Deep cryogenic treatments at − 196 °C soaking for 24 (DCT-24) and 48 (DCT-48) hours were conducted on the commercial annealed Ti–6Al–4V alloy. The methods of polarization and electrochemical impedance spectroscopy (EIS) were employed to evaluate the electrochemical behavior and corrosion mechanism. Furthermore, atomic force microscopy (AFM) was used to detect the corrosion surface. The results showed that deep cryogenic treatment shifted the corrosion potentials (E_corr) to the positive direction. The corrosion current densities (i_corr) of samples treated by DCT-24 and DCT-48 decreased from 153.1 nA·cm⁻² in the untreated (UT) sample to 86.3 nA·cm⁻² and 43.3 nA·cm⁻², respectively. Furthermore, the roughness of corrosion surfaces of samples subjected to DCT was smaller than that of the UT sample, which indeed demonstrated the improvement in corrosion resistance of Ti–6Al–4V alloy in Hank’s solution. The results of EIS test indicated that deep cryogenic treatment had no influence on the corrosion mechanism of Ti–6Al–4V alloy in Hank’s, while enhanced resistance value of outer porous layer R_p, which makes the surface more efficient to prevent the corrosion. The reduction of β-phase particles, improvement in dislocation density and release of residual stress caused by deep cryogenic treatment had great contribution to the improvement in corrosion resistance of Ti–6Al–4V alloy in Hank’s solution.