The effects of some anions on metastable pitting of 316 L stainless steel

摘要

The effects of PO~3- _4, CrO~2- _4, SO~2- _4 and NO~- _3 anions on metastable pitting of 316 L stainless steel in NaCl solutions were investigated using potentiostatic and potentiodynamic polariza- tion tests. The four anions all retard nucleation of metastable pitting. The inhibition effect decreases in the order: PO~3- _4＞CrO~2- _4＞SO~2- _4＞NO~- _3. The propagation rates of metastable pits are also decreased by the anions tested. Both metastable pitting potential E_m and stable pitting potential E_p increase almost linearly with the increase of each anion concentration, and have very close increasing slopes.