Comprehensive improvement of corrosion resistance and strength of ferrite-pearlite low alloy steel by cementite spheroidization treatment

In this work, the cementite spheroidization was realized by quenching and high-temperature tempering, which improved the anti-corrosion performance and strength of ferrite-pearlite low alloy steel. The spheroidized steel was composed of lath-shaped tempered ferrite matrix and nano-sized cementite particles, and the electron backscattered diffraction (EBSD) analysis revealed that grain refinement and dislocation strengthening of tempered ferrite were the reasons for its enhanced strength. The electrochemical and weight loss tests showed that the corrosion rate of the two steels increased with time due to the accumulation of cathodic cementite, which increased the cathodic-anode area ratio and enhanced the micro-galvanic effect. Compared to the as-received steel, the spheroidized steel demonstrated a slower corrosion rate during long-term immersion, which was attributed to the weaker micro-galvanic effect caused by reduced accumulation of cathodic cementite.