Study of the passivation and repassivation behavior of pure titanium in 3.5 wt% NaCl solution and 6 M HNO3 solution

We reveal differences in composition and structure of passive films and repassivation rate of titanium in 3.5 wt% NaCl and in 6 M HNO3. Titanium in 6 M HNO3 shows worse corrosion resistance than in 3.5 wt% NaCl due to higher defect concentration and lower TiO2 content despite the thicker passive film, which is the result of accelerated cathodic process and promoted dissolution/formation dynamic equilibrium of passive film in 6 M HNO3. Repassivation rate in 3.5 wt% NaCl is higher although film growth rate is lower, as the film exhibits good barrier effect when it is thin. Our results provide insights needed to guide application of titanium in SNFR plants.