Study on the Inhibitive Mechanism of Localized Corrosion of Stainless Steel by TUngstate

X-ray photoelectron spectroscopy (XPS) was used to study the com position and structure of passive film forming in the simulated occluded corrosion cell (OCC) of AISI304 stainless steel in NaCl solution containing tungstate, and the inhibitive mechanism of localized corrosion of stainless steel by tungstate. The results showed that outside passivating film was mainly composed of WO4 2-, CrO3, CrCl3, FeCl2 and FeCl3, as also a little Ni2O3, Fe2O3, CrO42-, γ-FeOO Hand Fe(OH)3. The inside film sputtered 5 minutes was composed of Cr2O3, C rOOH, Cr(OH)3, FeCl2, FeCl3 and WO3, in addition a little WO2 and WO42-. WO42- moving into OCC could replace the whole or part of Cl- adsorbing on metal surface, and react with Fe2+ to form Fe3+ and WO2, then produce indissoluble compounds Fe2(WO4)3 and FeWO4 to cover on the anodic area. The protective film could slow down the self-catalysis effect in the OCC, thus could prohibit the farther development of localized corrosion.