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 M_xC_y 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

中文翻译：

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珠光体材料的显微组织及晶界腐蚀机理

研究了低合金耐候钢S500AW珠光体组织和晶界局部腐蚀萌生和扩展的影响机制。通过金相显微镜、XRD、SEM、TEM和EBSD光谱对材料的结构进行了研究。SKPFM研究了低合金钢基体表面组织间的表面电位。溶液浸渍实验用于研究腐蚀起始阶段的材料结构和晶界现象。结果表明，组织中存在位错、高内应力等缺陷会导致腐蚀的优先发生。珠光体内部的铁素体优先经历腐蚀过程，而周围的铁素体经历缓慢腐蚀过程。他们晶界处的_x C _y析出物在此过程中逐渐脱落，形成凹坑。析出物中Cr的存在会导致基体中缺乏Cr，从而影响材料的耐腐蚀性能。

图形摘要