Cu和Mg对Al-7Si铸造合金耐腐蚀性能的影响

Effects of Cu and Mg on Corrosion Resistance of Al-7Si Cast Alloy

采用电化学腐蚀试验和浸泡腐蚀试验,研究了Al-7Si铸造合金在质量浓度为3.5%NaC1水溶液中的腐蚀行为,探讨了合金元素Cu、Mg对Al-7Si合金的塔菲尔曲线以及自腐蚀电位、腐蚀电流密度等电化学参数的影响,并利用电子分析天平和扫描电镜,分别对各合金浸泡腐蚀后的质量损失和腐蚀形貌进行了测量与分析。结果表明,各试验合金均较快进入钝化状态,随着合金元素Cu、Mg的加入,各合金自腐蚀电位均向负向移动、腐蚀电流密度增高,腐蚀质量损失增大,耐腐蚀性能降低。与Mg元素相比,Cu元素对合金耐腐蚀性影响较大,使其腐蚀机理由点状腐蚀转变为晶间腐蚀。

The corrosion behaviors of A1-7Si cast alloys in 3.5%NaC1 aqueous solution were examined by using electrochemical and immersion corrosion tests. The influence of copper （Cu） and magnesium （Mg） on the Tafel curves and electrochemical parameters, such as free corrosion potential and corrosion current densities, of A1-7Si alloys were investigated. Moreover, the mass loss and morphology of each alloy after immersion corrosion were measured and analyzed by analytical balance and scanning electron microscopy. The results indicate that all the tested alloys can be passivated rapidly, their corrosion potential drifts to negative, their corrosion current density and corrosion mass loss increase with the addition of alloy elements Cu and Mg. Compared with element Mg, element Cu has a greater effect on the corrosion resistances of A1-7Si alloy, and can convert the corrosion mechanism of the alloy from pitting corrosion into intergranular corrosion.