Synergy corrosion effect of thiosulfate and sulfide on Q235 steel in sodium aluminate solution

Synergy corrosion effect of thiosulfate and sulfide on Q235/ASTM steel in the sodium aluminate solutions containing fixed S2- content was studied by high temperature and immersion corrosion, scanning electron microscopy (SEM), x-ray diffraction (XRD) and electrochemical measurements. The corrosion mechanism of Q235/ASTM steel was also discussed combining with the polarization curve and electrochemical impedance spectroscopy (EIS). The results indicated that the aluminum oxide layer of Q235/ASTM steel surface was damaged, the surface corrosion of Q235/ASTM steel was dense and had good adhesion with the matrix in the low concentration of 3 g . L-1 S2O32- with the lower corrosion rate, the presence of lower concentration S2O32- acts as an inhibitor for the corrosion of Q235/ASTM steel. The corrosion products were composed of sulfide (FeS, FeS2 and MnS) and fenosoferric oxide (Fe3O4) by XRD analysis. The polarization curves and electrochemical impedance spectroscopy test results showed that Q235/ASTM steel was in active state at corrosion potential, the anodic dissolution reaction of Q235/ASTM steel was mainly controlled by the electrochemical reaction. The corrosion resistance of steel in the 3 g . L-1 S2O32--containing solutions was higher than 4 g . L-1 and 6 g . L-1 S2O32--containing solutions.