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为满足桥梁支座用铸钢在海洋大气环境下的耐蚀性要求,设计了2种成分的Cr-Ni-Cu系耐腐蚀低合金铸钢。采用周浸加速腐蚀试验、实地大气暴露试验考察试验钢在海洋大气环境中的腐蚀行为,并结合扫描电镜、XRD、电化学手段分析了合金元素对锈层和电化学行为的影响。结果表明,2种成分的Cr-Ni-Cu系低合金铸钢的耐蚀性均较好,随着时间延长,耐蚀铸钢腐蚀率下降并达到稳定,而对比钢种20MnSi腐蚀率保持下降趋势,未达到稳定状态。周浸腐蚀316h后耐蚀铸钢与20MnSi腐蚀率差距变小;Cr元素在内锈层中呈条带状富集,有效阻碍了Cl-的扩散,Ni的加入提高钢的自腐蚀电位,促进γ-FeOOH向α-FeOOH的转化,增加锈层稳定性;Cr、Ni、Cu的复合加入增大了铸钢的电荷传递电阻,提高了耐蚀性。
In order to meet the requirement of corrosion resistance of cast steel for bridge support in marine atmosphere, two kinds of Cr-Ni-Cu alloy corrosion-resistant low alloy cast steel were designed. The effects of alloy elements on rust layer and electrochemical behavior were analyzed by means of immersion accelerated corrosion test and field atmospheric exposure test. The corrosion behavior of test steel in marine atmospheric environment was investigated by SEM, XRD and electrochemical measurements. The results show that the corrosion resistance of Cr-Ni-Cu low-alloy castings with two compositions is good, with the extension of time, the corrosion resistance of cast steel decreases and stabilizes, while the corrosion rate of 20MnSi of the comparative steel keeps decreasing Trend, did not reach a steady state. The difference of corrosion rate between corrosion-resistant cast steel and 20MnSi is smaller after 316h immersion etching. The Cr element is enriched in strip in the inner rust layer, which effectively impedes the diffusion of Cl-. The addition of Ni increases the self-corrosion potential of steel and promotes γ-FeOOH to α-FeOOH conversion, increase the stability of the rust layer; Cr, Ni, Cu compound added to increase the cast steel charge transfer resistance and improve the corrosion resistance.