高强度铝合金2A12的大气腐蚀电化学行为及规律研究

Study of electrochemical behaviors of high strength aluminum alloy 2A12

采用室内周浸模拟加速实验,电化学阻抗谱(EIS)及SEM研究了2A12铝合金在模拟距海点相对较远处的大气环境中的电化学腐蚀行为及规律.实验结果表明,2A12铝合金在NaCl的质量分数为0.5%的NaCl溶液中周浸后的腐蚀形态主要是点蚀和晶间腐蚀,Cl-是促进点蚀发生发展的主要原因.在不同的周浸时间,2A12铝合金的Nyquist曲线均由一个高频端压缩容抗弧和一个中低频端Warburg阻抗组成.周浸时间为120 h时,腐蚀产物电阻达最小值.表明腐蚀早期,腐蚀产物对电极反应的阻滞作用小,粒子在电极表面腐蚀产物膜中的扩散过程起主导作用,随周浸时间的延长,腐蚀产物对电极反应的阻滞作用不断增强,腐蚀速度减缓.

The electrochemical behaviors of aluminum alloy(2A12) was investigated by using alternate immersion test,scanning electron microscopy(SEM) as well as electrochemical impedance spectroscopy(EIS) technique.The results showed that obvious localized attack,mainly pitting corrosion and intergranular corrosion occurred on the surface of 2A12 after immersed in 0.5%NaCl solution.The occurrence and propagation of pitting corrosion were mainly attributed to the presence of chloride ions.Under different stage,Nyquist curves of 2A12 consist of a capacitance arc at high frequencies and a Warburg impedance at low frequencies in the solution of 0.5% NaCl.After 120 h alternate immersion,corrosion product resistance appeared a minimum value,indicating that in the initial stage,the diffusion process dominates the interfacial corrosion reaction,which is due to a very slight block effect of the corrosion product.With the increase of time,corrosion rate became slower because of the stronger block effect.