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采用光学金相技术结合交流阻抗测量,分析了三种低合金钢在模拟的沿海大气环境中的初期腐蚀行为.实验发现,显微组织直接决定钢的初期腐蚀行为并间接影响长期腐蚀行为.在腐蚀初期,铁素体钢中的大角晶界易于被择优腐蚀,而贝氏体内的小角晶界的择优腐蚀趋势较弱,铁素体+珠光体钢的择优腐蚀集中于珠光体及其边界.铁素体裸钢有较强的耐腐蚀性,但其锈层电阻随腐蚀时间增加产生的增量较小;贝氏体与铁素体+珠光体裸钢的耐腐蚀性较差,但其锈层电阻随腐蚀时间增加产生的增量较大,长期腐蚀性能更优.这些结果表明,在适当合金化后,贝氏体作为新型低成本高强度耐候钢的基本组织极具应用潜力.
The initial corrosion behavior of three low-alloy steels in the simulated coastal atmospheric environment was analyzed by means of optical metallography and AC impedance measurement.The results show that the microstructure directly determines the initial corrosion behavior of steel and indirectly affects the long-term corrosion behavior. In the early stage of corrosion, the large-angle grain boundaries in ferritic steels tend to be preferentially corroded, while the preferred corrosions in small-angle grain boundaries in bainite tend to be weak. Preferential corrosion of ferrite + pearlite steels concentrates on pearlite and its boundaries. Ferritic bare steel has strong corrosion resistance, but its rust resistance increases with the increase of corrosion time. The corrosion resistance of bainite and ferrite + pearlite bare steel is poor, but The corrosion resistance of the rust layer increases with the increase of the corrosion time, resulting in better long-term corrosion resistance.These results show that bainite has potential application as the basic structure of the new low cost and high strength weathering steels after proper alloying.