Unraveling the effect of Al2O3-MnS complex inclusion on the pitting corrosion behavior of dual phase steel

Pitting corrosion behavior of dual phase steel triggered by Al2O3-MnS complex inclusion in NaCl solution was investigated. Results indicated that neither micro -defects nor strain fields existed around the insulating Al2O3- MnS inclusion, but an open circular pit was immediately initiated around the inclusion and grew in diameter approaching 200 mu m in several minutes. The preferential dissolution of unstable MnS part created local acidic electrolytes promoting the dissolution of Al2O3 part and adjacent matrix. The radial diffusion and hydrolysis of Al3+ acidified the pit solution, resulting in the propagation of circular pit. Finally, the pitting propagation decelerated with the depletion of inclusion.