Effect of Chromium on Microstructure and Corrosion Behavior of High-Cr White Cast Irons Used in Coal-Fired Power Plant Desulfurization Facilities

The findings of this study provide valuable insights into the electrochemical characteristics of high-chromium white cast irons (HCCIs) and their suitability as impellers in flue-gas desulfurizer (FGD) slurry pumps of coal-fired power plants. By evaluating the corrosion and wear resistance of HCCI specimens with varying Cr contents, it was confirmed that the corrosion mechanism of HCCI involves micro-galvanic corrosion between the matrix and iron–chromium and carbon intermetallic compounds. Furthermore, the study revealed that HCCI with 32 wt% Cr content exhibited superior corrosion resistance, owing to the full-ferrite matrix with complete Cr dissolution that facilitated the enrichment of Cr(OH)₃ and Cr₂O₃ on the HCCI surface. The results demonstrate that the addition of 32 wt% Cr to HCCI enhances its passivation ability and improves its ability to resist both micro-galvanic corrosion and erosion–cavitation. Finally, the performance of the impeller fabricated with HCCI containing 32 wt% Cr was validated in a real environment for 16 months with a FGD slurry pump, and it was found to be in excellent condition, further highlighting the effectiveness of HCCI for use as impellers in FGD slurry pumps.