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通过设计热处理工艺使耐候钢中所含硼元素发生不同程度的晶界偏聚,并结合采用扫描电镜、能谱分析和电化学方法研究偏聚对该合金钢腐蚀行为的影响。结果表明:硼的晶界偏聚越强,样品的局部腐蚀就越严重,其表现就是钢基体-锈层界面愈加不平整。晶界硼偏聚首先对该钢初期腐蚀有促进作用,硼的晶界偏聚促进晶界择优腐蚀。在硼明显偏聚的样品的表面形成锈层后,腐蚀会沿晶界深入基体。致密锈层对Cl-的渗透有阻碍作用,使得靠近基体的内锈层中Cl-含量及Cl-/Na+比均低于远离基体的外锈层。电化学结果表明,试样偏聚的加重使得锈层腐蚀电流密度逐渐增大,自腐蚀电位也逐渐向负方向偏移,锈层整体上表现出保护性减弱。
Through the design of heat treatment process, boron in weathering steels was segregated at different grain boundaries, and the influence of segregation on the corrosion behavior of the alloy steel was studied by SEM, EDS and electrochemical methods. The results show that the stronger the segregation of boron in the grain boundaries, the more severe the localized corrosion of the sample is. The more the interface between the steel substrate and the rust layer is, the more uneven the surface is. Boron segregation at the grain boundary first promotes the initial corrosion of the steel. Boron grain boundary segregation promotes the selective corrosion of grain boundaries. After the surface of the sample in which boron is obviously segregated, rust forms and the corrosion proceeds deep into the matrix along the grain boundaries. The tight rust layer impedes the infiltration of Cl-, so that Cl- content and Cl- / Na + ratio in the inner rust layer close to the substrate are lower than the outer rust layer away from the substrate. The results of electrochemical tests show that the corrosion current density of the rust layer increases gradually with increasing segregation of the sample, and the corrosion potential also gradually shifts toward the negative direction, and the rust layer as a whole shows weakened protection.