AZ91D镁合金电偶腐蚀的扫描Kelvin探针研究

Galvanic Corrosion Evaluation Behavior of AZ91D Magnesium Alloy Studied by Scanning Kelvin Probe

摘要:

利用扫描Kelvin探针技术(SKP)研究AZ91D镁合金与316L不锈钢偶接件在盐雾试验中电偶腐蚀规律。通过在中性盐雾试验不同周期的表面腐蚀形貌的观察和伏打电位分布图的测量结果分析表明，AZ91D镁合金电偶腐蚀效应与偶接阴阳极的伏打电位差密切相关，AZ91D镁合金与316L不锈钢偶接件存在较大的电位差(约为–1.28 V)，其电偶腐蚀效应非常显著。在盐雾试验初始阶段，腐蚀主要发生在偶接界面AZ91D镁合金一侧，该腐蚀区域的伏打电位增加幅度较大，而316L不锈钢受到保护没有发生明显腐蚀。随着盐雾试验时间的延长，AZ91D镁合金腐蚀加快，腐蚀产物覆盖区域不断扩大，24 h盐雾试验后，偶接件的平均伏打单位差由原始的–1.29 V增加到–1.53 V，AZ91D镁合金的电偶腐蚀效应加大。由于AZ91D镁合金在盐雾中生成的腐蚀产物对基体具有一定的保护作用，当腐蚀产物不断增加并覆盖表面，偶接件的电位差减小导致AZ91D镁合金的电偶腐蚀效应降低

Abstract:

The galvanic corrosion of an AZ91D magnesium alloy coupled with 316L stainless steel using accelerated testing in salt spray fog has been investigated by using the scanning Kelvin probe (SKP) technique. The results show that the galvanic effects for AZ91D magnesium alloys are affected by the potential difference between anode and cathode by analyzing corrosion products and SKP Volta potential maps. The galvanic effect of AZ91D magnesium alloy coupled with 316L stainless steel is very significant during accelerated testing in the initial stage of salt spray fog because the potential difference between AZ91D magnesium alloy and 316L stainless steel is about –1.28 V. The galvanic corrosion occurs mainly in the interface near AZ91D magnesium alloy, and 316L stainless steel has no obvious corrosion. With the salt spray test time increasing, the corrosion of the AZ91D magnesium alloy is accelerated and the coverage area of corrosion products expanded. The Volta potential difference of galvanic sample increases from –1.29 V to –1.53 V after 24 h salt spray test. The galvanic corrosion effect of AZ91D magnesium alloy is increased. The corrosion products of AZ91D magnesium alloy have a protective effect. The galvanic corrosion effect is reduced when the corrosion product increases to cover the surface of the specimen