Effect of Anion on Protection of Corrosion Product Film of Iron-Rich Phase Ferrous Sulfide on P110 Steel Surface

The effect of two anionic solutions (Na₂SO₄ and NaHCO₃) on the protection of the corrosion product film, iron-rich phase ferrous sulfide (FeS_1-x), on the surface of P110 steel was studied through Mott-Schottky method and weight loss method. The changes of protection were explained by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The results show that the corrosion product film immersed in Na₂SO₄ solution was more prone to electron transfer and solute diffusion, and exhibited p-type semiconductor characteristics and poor protection. The electron transfer and solute diffusion were slowed down in the corrosion product film immersed in NaHCO₃ solution, and the corrosion product film exhibited n-type semiconductor characteristics and good protection.