Elucidating the effect of titanium alloying on the pitting corrosion of ferritic stainless steel

Ferritic stainless steels have been utilized in marine atmosphere and are found to be susceptible to pitting corrosion in our field investigation. Alloying is an important to modify the passive film on the surface and improve the pitting corrosion resistance. Nevertheless, how the addition of titanium modifies the passive film and affects the pitting corrosion resistance of ferritic stainless steels remain controversial. This study has elucidated these topics through microstructure analysis and corrosion properties analysis. The results demonstrate that titanium addition increases the pitting potential almost linearly. Titanium forms TiO2 in the passive film and reduces defect density of the passive film. Moreover, titanium addition induces the precipitation of the Laves phase, which promotes micro-galvanic corrosion. For the titanium-alloyed ferritic stainless steels, pitting corrosion predominantly occurs in the ferrite phase adjacent to the Laves phase. The influence mechanism of titanium on the pitting corrosion of the ferritic stainless steel has been established, which takes micro-galvanic corrosion induced by titanium addition into account.