Microstructure and Grain Boundary Corrosion Mechanism of Pearlitic Material

The influence mechanism of the localized corrosion initiation and expansion of the pearlite structure and the grain boundaries of low-alloy weathering steel S500AW was studied. The structure of the material was studied by means of metallographic microscope, XRD, SEM, TEM and EBSD spectrum. The surface potential between structures on the surface of low-alloy steel substrate was studied by SKPFM. The solution immersion experiment was used to study the material structure and grain boundary phenomena in corrosion initiation stage. The results showed that the existence of defects such as dislocations and high internal stress in the organization will lead to the preferential occurrence of corrosion. The ferrite inside the pearlite underwent corrosion process preferentially, while the surrounding ferrite underwent slow corrosion process. The MxCy precipitate at the grain boundary gradually fell off with this process to form pits. The presence of Cr in the precipitate would lead to the lack of Cr in the matrix, which would affect the corrosion resistance of the material. Graphic Abstract

Automated summary

The study found that defects in low-alloy weathering steel S500AW can lead to corrosion, especially with the ferrite inside the structure being more susceptible to corrosion. Precipitates at grain boundaries gradually fall off to form pits, affecting the corrosion resistance of the material.