Effects of Rare Earth Elements on Microstructure and Corrosion Resistance of Low Alloy Steel Based on Ultra-Thin Cast Strip Process

This laboratory study aimed to reveal the inner connects between the microstructure and corrosion properties of a RE microalloyed ultra-thin cast strip (UCS) steel. The microstructure mainly consisted of homogeneous polygonal ferrite (PF) with a small amount of pearlite (P), while adding multiple alloying elements led to the appearance of granular bainite (GB) and bainitic ferrite (BF). RE elements strongly promoted the homogenization and refinement of microstructure by segregating towards the solid–liquid interface. Potentiodynamic polarization, EIS, and weight loss curves under wet–dry immersion test confirmed that the corrosion behavior was significantly improved by RE, while the addition of RE had no obvious change on tensile strength. The corrosion resistance of the homogeneous single-phase microstructure was proved to be better than that of multiphase microstructure. Hence, RE had a remarkable influence on improving corrosion resistance when the experimental steels processed single-phase microstructures.