General Corrosion Behavior of High Chromium Cast Iron in an Acid Solution

The effect of carbon addition on the general corrosion behavior of high-chromium cast iron (HCCI) was studied by a scanning electron microscope with energy dispersive spectroscopy (SEM-EDS) or electron back-scattered diffraction (EBSD), or electrochemical polarization techniques in 0.1 mol dm(-3) H2SO4 + 0.05 mol dm(-3) HCl at room temperature. The addition of 2.1-2.8 wt% carbon to HCCI increased the fraction of eutectic austenite and eutectic carbide phases, while that of HCCI decreased the fraction of the primary austenitic phase. Potentiostatic polarization of the HCCI at -0.35 V-SSCE or 0.0 V-SSCE resulted in preferential general corrosion of the primary austenitic or eutectic austenitic phases, respectively. The decrease in corrosion current density and the shift in noble corrosion potential direction with increasing carbon content in the HCCI indicated that the fraction and the chemical composition of austenitic (primary and eutectic) and carbide phases were strongly related to the general corrosion behavior of the HCCI.