Pitting resistance of anodic passive films formed on 316L stainless steel in the concentrated artificial seawater

The pitting resistance of anodic passive films formed on 316L stainless steel was studied in the concentrated artificial seawater with the concentration ratio (c _R) ranged from 1.5 to 3 times under typical operation temperature condition of multi effect distillation (MED) by using the polarization curve and Mott-Schottky analysis. The pitting potential decreases linearly with the logarithm of c _R. The anodic passive films are characterized by both n- and p-type semiconductive behavior, i.e., a bilayer microstructure. The density values of defects (i.e. N _D and N _A) are in the range of 10²⁰ to 10²¹ cm^?3, and increase with c _R linearly. According to the point defect model (PDM), the increase of both Cl^? concentration and defect density N _D can facilitate the absorption of Cl^? ions in the passive films, which is mainly responsible for the deterioration of pitting resistance in the concentrated artificial seawater.