Cr-Ni-Cu系低合金铸钢在海洋大气环境中的腐蚀行为

Corrosion behavior of Cr-Ni-Cu low alloy cast steel in marine atmospheric environment

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。

To meet the corrosion resistance requirements of cast steels for bridge bearings in marine atmospheric environment,two kinds of Cr-Ni-Cu low alloyed cast steels with excellent corrosion resistance were designed.Periodic immersion accelerated corrosion test and field atmospheric exposure test were carried out to investigate the corrosion resistance of the designed steels in marine atmosphere,then the effect of alloy elements on rust layer and electrochemical behavior was analyzed by SEM,XRD,electrochemical methods.The results indicate that the designed Cr-Ni-Cu low alloyed cast steels show better corrosion resistance than 20 MnSi.The corrosion rate of corrosion resistant cast steel decreases gradually to a stable level,while the corrosion rate of 20 MnSi keeps downward trend,and does not reach stability.And the difference of corrosion rate between them becomes smaller after cyclic immersion corrosion for 316h;the Cr element enriched in the inner rust in form of banding can withstand the diffusion of Cl-.Besides,the additions of Ni raise the self-corrosion potential of the bare steel and promote the transformation fromγ-FeOOH toα-FeOOH,and then improve the stability of the rust;the charge transfer resistance of cast steel increases with the combined addition of Cr,Ni and Cu,and thus corrosion resistance of steels is enhanced.