长江淡水环境中 42CrMo 和不锈钢的电偶腐蚀行为研究

Galvanic corrosion behavior of 42CrMo and stainless steel in Yangtze River freshwater environment

摘要

[目的] 研究长江淡水环境中 42CrMo 低合金钢与 410 不锈钢在电偶接触状态下的腐蚀行为，明确电偶效应对两类材料腐蚀速率的加速/抑制规律，为水电站工程中的异种金属连接件选材与防护提供理论依据。[方法] 采用静态浸泡实验在真实长江淡水水样中分析不锈钢电偶对作用下 42CrMo 钢在不同周期的腐蚀速率，利用电化学阻抗谱测试分析其表面状态变化规律，定期监测电偶电流和电位。[结果] 电偶作用显著加速了 42CrMo 钢的腐蚀，其平均腐蚀速率达 0.198 mm/a，约为无电偶对时的 4 倍。不锈钢电偶对对 42CrMo 钢腐蚀的贡献度远超其他离子，表明异种金属接触引发的电偶腐蚀是影响 42CrMo 钢腐蚀速率的主要因素。[结论] 长江淡水环境中，42CrMo 钢与 410 不锈钢直接接触易引发阳极材料严重的电偶腐蚀。工程应用需避免异种金属直接连接，宜采用绝缘涂层隔离或阴极保护技术对 42CrMo 低合金钢进行防护。

Abstract

[Objective] To investigate the corrosion behavior of 42CrMo low-alloy steel and 410 stainless steel under galvanic contact in the fresh water of the Yangtze River, clarify the acceleration/inhibition effect of the galvanic coupling on corrosion rates of the two materials, and provide a theoretical guidance for material selection and protection of dissimilar metal connections in hydropower engineering. [Method] Static immersion tests were conducted in authentic Yangtze River fresh water samples to evaluate the corrosion rate of 42CrMo steel coupled with 410 stainless steel over varying periods. Electrochemical impedance spectroscopy (EIS) was employed to analyze the evolution of surface state, and galvanic current and potential were continuously monitored. [Result] The galvanic effect significantly accelerated the corrosion of 42CrMo steel, with an average corrosion rate of 0.198 mm/a, approximately four times that without the galvanic couple. The contribution of the stainless steel galvanic couple to the corrosion of 42CrMo steel far exceeded that of other ions, including that galvanic corrosion induced by contact between dissimilar metals is the main factor affecting the corrosion rate of 42CrMo steel. [Conclusion] In the fresh water of the Yangtze River, direct contact between 42CrMo steel and 410 stainless steel readily causes severe galvanic corrosion of the anodic material. In engineering applications, direct connection of dissimilar metals should be avoided, and protective measures such as insulating coatings or cathodic protection should be adopted to protect the 42CrMo low-alloy steel.

关键词

低合金钢 / 不锈钢 / 电偶腐蚀 / 淡水

Key words

low-alloy steel / stainless steel / galvanic corrosion / freshwater

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