AZ91D镁合金电偶腐蚀的研究

在自来水和3.5%NaCl溶液中测试了铸造AZ91D镁合金与铝合金、锌合金、Q235碳钢和Cu偶合后的电偶腐蚀行为，研究了腐蚀环境、偶接材料和阴阳极面积比(CAAR)对铸造AZ91D镁合金电偶腐蚀行为的影响。在电偶腐蚀过程中测量溶液的pH值以及电偶腐蚀电流；用失重法计算了铸造AZ91D镁合金的电偶腐蚀速率，利用SEM观察了AZ91D镁合金的腐蚀形貌，并对腐蚀产物进行XRD分析。结果表明，AZ91D镁合金在电偶腐蚀过程中会使溶液的pH值升高，并伴有以Mg(OH)₂为主的腐蚀产物的生成；溶液中Cl^-的存在会加速AZ91D镁合金的电偶腐蚀速率；低氢过电位金属Q235碳钢和Cu对AZ91D镁合金的电偶腐蚀加速效果明显高于中氢过电位金属铝合金和锌合金，偶接材料的极化性能对AZ91D镁合金的电偶腐蚀速率有较大影响。同时，大的阴阳极面积比会加速AZ91D镁合金的电偶腐蚀速率，且AZ91D镁合金的电偶腐蚀电流随阴阳极面积比的增大而呈线性增长趋势。

Galvanic Corrosion of AZ91D Magnesium Alloy

The galvanic corrosion behaviors of AZ91D magnesium alloy coupled with aluminum alloy, zinc alloy, Q235 carbon steel and copper were investigated in tap water and 3.5%NaCl solution. The effects of corrosion environment, coupled material and cathode to anode area ratio (CAAR) were discussed. During the corrosion process, pH of the electrolyte was measured and the galvanic currents of all couples were recorded. Meanwhile, the corrosion rate of AZ91D magnesium alloy was calculated by mass loss method, the corrosion morphologies of AZ91D were observed by SEM and the corrosion products were analyzed by XRD. The results showed that the pH of the electrolyte increased due to the galvanic corrosion of AZ91D magnesium alloy, the main corrosion product was Mg(OH)₂, and the addition of NaCl would accelerated the galvanic corrosion rate of AZ91D magnesium alloy. Coupled materials with low hydrogen overpotential would promote the galvanic corrosion of AZ91D magnesium more seriously than that with middle hydrogen overpotential, the polarization property of coupled materials also had an obvious effect on galvanic corrosion of AZ91D magnesium alloy. Moreover, larger CAAR would result in faster galvanic corrosion, and the galvanic current of AZ91D magnesium alloy increased linearly with the increase of CAAR.