Effect of Cl ^- on corrosion behavior of alloy 690 in high temperature and high pressure water solution

The effect of Cl ^- on the corrosion behaviors of alloy 690 in high temperature and high pressure solution was investigated by SEM and XRD. The results show that the conditions of inside and outside surface have apparent effect on the corrosion morphology of alloy 690. The surface of passive film formed in solution with Cl ^- is uneven, and a lot of pits can be found. The Cl ^- of electrolyte has great effect on the structure of corrosion product. The corrosion product film formed in solution without Cl ^- has the double layer structure. The corrosion scale formed in the Cl ^--containing solution has a monolayer. The outer sub-film is composed of grainy crystal. The XRD results show that the passive film in the two environments mainly consists of Cr ₂O ₃, NiFe ₂O ₄, NiO and other oxides, but there is fewer oxides in the film formed in solution with Cl ^-.