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The distribution characteristics of corrosion-resistant elements in low-alloy steel affected the initial corrosion behavior of matrix. In this article, the segregation behavior of elements at grain boundaries and pearlite defects in low-alloy steel and the precipitation behavior of Cu in inclusion had been studied. The precipitation of Cu in the inclusion was beneficial to the reduction of grain boundary segregation. And Cu had the ability to capture Sb and Ni. Cu was involved in the local corrosion initiation of inclusions, during which Cu and Sb were oxidized to corresponding Cu2O and Sb2O3, and distributed in the corrosion products. Under the influence of the segregation of elements at the grain boundaries, the local corrosion spreading process was carried out, and the internal part of the crystal was preferentially corroded. Cr was enriched in the cementite of pearlite and took part in the corrosion process, resulting in the formation of CrO3.

The distribution characteristics of corrosion-resistant elements in low-alloy steel affected the initial corrosion behavior of the matrix. In this article, the segregation behaviors of elements at grain boundaries and pearlite defects in low-alloy steel Q500 and the precipitation behavior of Cu in inclusions were studied. Cu, Ni and Sb had segregation behavior at the boundary of the inclusions, which was beneficial for reducing grain boundary segregation. Cu had the ability to capture Sb and Ni. Cu and Sb involvement in local corrosion process of inclusions were observised by multi-cycle 3.5% NaCl immersion test, during which Cu and Sb were oxidized to corresponding Cu2O and Sb2O3. Under the influences of the segregation of elements at the grain boundaries, the internal part of the crystal was preferentially corroded. Cr was enriched in the pearlite cementite, formed (Cr,Fe)7C3 and contributed to the corrosion process, forming Cr2O3 and CrO3.

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