Corrosion behaviors of Fe-based amorphous coatings in Cl-containing solutions at different temperatures and pH values

The effects of solution temperature and pH value on the corrosion behavior of Fe-based amorphous coatings (Fe-based AMCs) were systematically investigated. The results indicate that elevated temperature enhances the interaction between corrosive ions and the coating surface, accelerates the anodic reaction kinetics, and consequently leads to thickening of the passive film. However, higher solution temperature also promotes an increase in point defect concentration, a decrease in electron work function, and the formation of Cr(OH) 3 within the passive film, ultimately reducing the corrosion resistance of the coating. Furthermore, the dissolution current density is sensitive to the concentrations of c S O 4 2 − / c H S O 4 − and c O H − in Cl − -containing solutions, increasing with their concentrations. In strongly alkaline NaCl solutions, the higher content of point defects and greater amount of poorly water-soluble Cr(OH) 3 in the passive film may facilitate easier penetration of Cl − ions into the film, thereby weakening the corrosion resistance of the coating. In addition, the potential possible corrosion mechanisms related to HSO 4 − /SO 4 2− and OH − ion adsorption as well as Cl − ion penetration are further proposed.