Growth of corrosion product film on 12Cr1MoV steel in sulfur-containing sodium aluminate solution

Abstract

The growth mechanism of product film on steel surface in sulfur-containing sodium aluminate solution was studied with relevance to processing of high-sulfur bauxite ores in Bayer process. Scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) were used to study the growth of corrosion product film on 12Cr1MoV steel in sodium aluminate solution containing 5 g/L S2– and 3 g/L S2O2– 3. Results indicated that the corrosion rate gradually decreased with increasing corrosion time (t). The fitted corrosion rate equation was V = 4.365t–0.809. The corrosion resistance was highest after 5 d. The growth evolution of the product film was divided into three stages: film formation, film conversion and film growth. The final corrosion product film comprised an inner film layer mainly composed of Fe3O4 and an outer film layer mainly composed of FeS, FeS2 and Fe2O3.