合金元素对铸造Al-Si合金腐蚀性能的影响

The influences of alloying elements on the corrosion properties of as-cast Al-Si alloy

采用电化学实验和浸泡腐蚀实验研究了Al-7%Si合金在3.5%NaC1溶液中的腐蚀行为,同时还探讨了合金元素Cu,Mg,Mn,Sn对Al-7%Si合金开路电压、腐蚀电流密度和自腐蚀性能的影响规律,并利用扫描电镜对各合金浸泡腐蚀前后的形貌进行了观察与分析.电化学实验结果表明,所有实验合金均较快进入钝态,随着各合金元素的加入,实验合金的自腐蚀电位向负向移动,腐蚀电流密度增加.浸泡腐蚀实验结果表明,加入的合金元素均降低了Al-7%Si的腐蚀性能,其中Cu影响较大,使合金由点蚀转变为晶间腐蚀.

The corrosion behaviour of Al-7%Si alloys in 3. 5%NaCl solution has been studied by electrochemical and immersion corrosion tests, at the same time, the effect of Cu,Mg,Mn and Sn on corrosion potentials, corrosion current densities and corrosion behaviour of Al-7%Si alloys have been researched in this paper. The morphology of alloys before and after immersion corrosion were analyzed by SEM （scanning electron microscopy）. The results of electrochemistry tests indicate that all the tested alloys may be passivated rapidly. The free corrosion potentials shifted to negative and the corrosion current densities of the alloys grew with increasing alloy elements. The results of immersion corrosion tests show that corrosion resistance of Al-7%Si alloy is decreased when it content the testing alloying elements. The most influence element is Cu. The mode of corrosion changed from pitting corrosion to inter-granular corrosion due to the addition of Cu into the alloy.