The effect of Cl - /SO 4 2- molar ratio on the corrosion behavior of Zr 41.2 Ti 13.8 Cu 12.5 Ni 10 Be 22.5 metallic glass was systematically investigated in mixed MgCl 2 and MgSO 4 solutions with molar ratios of 1:0, 9:1, 7:1, 5:1, 4:1, 3:1, and 0:1. Within the molar ratio range 9:1 to 2:1, decreasing Cl - concentration resulted in a rightward shift of the polarization curves and an elevation of the corrosion potential from -198.8 mV to 18.3 mV. The lowest corrosion current density, the highest pitting potential, and the widest width of the passive region were observed at a Cl - /SO 4 2- molar ratio of 5:1, indicating optimal corrosion resistance under this condition. Notably, no pitting corrosion occurred in pure SO 4 2- solution, whereas the most severe pitting was observed in pure Cl - solution. As the Cl - concentration decreased, the severity of pitting corrosion progressively diminished. At a molar ratio of 2:1, both localized pitting corrosion and “earthen embankment-like” corrosion product deposits were observed on the metallic glass surface. This study identifies a critical Cl - /SO 4 2- molar ratio threshold of 5:1. Above this molar ratio, SO 4 2- inhibits corrosion, while below it, SO 4 2- enhances Cl - -induced pitting corrosion. X-ray photoelectron spectroscopy (XPS) analysis revealed prominent signals corresponding to Zr 4+ , Ti 4+ , Cu + , and O1s, confirming the formation of a protective passive film primarily composed of TiO 2 and ZrO 2 . This oxide layer effectively impedes further interaction between the metallic glass and the corrosive environment. This advances our understanding of the corrosion behavior and mechanisms of metallic glasses in Cl - and SO 4 2- containing solutions, facilitating their application in corrosion protection.
Xue et al. (Sun,) studied this question.