采用SECM分析7075铝合金的局部腐蚀行为

使用0.6mol/LNaCl溶液腐蚀7075铝合金,采用扫描电化学显微镜进行逼近曲线、面扫描测试,用X射线衍射仪对合金的形貌进行分析,用能谱仪分析腐蚀产物成分,研究7075铝合金局部腐蚀电化学机理.结果显示:逼近曲线呈现正反馈,探针的电流随着与合金基底距离的减小变大;合金表面的活性点因为氯离子活化作用不断增加,形成大范围的点蚀;氯离子通过吸附在合金表面钝化层并与之反应,破坏钝化层使得内部裸露,内部的第2相电极电位更负,和铝基体构成腐蚀微电池,第2相的阳极腐蚀溶解降低合金的强度和抗腐蚀能力.

Analysis of local corrosion of 7075 aluminum alloy by SECM

The 0.6 mol /L NaCl solution was used to corrode 7075 aluminum alloy, and the approximation curve and surface scanning test were carried out by scanning electrochemical microscope. The morphology of the alloy was analyzed by X-ray diffractometer, and the composition of corrosion products was tested by energy spectrometer to study the electrochemical mechanism of local corrosion of 7075 aluminum alloy. The results show that the approximation curve presents positive feedback, and the current of the probe increases with the decrease of its distance from the alloy substrate; the active spots on the surface of the alloy form a wide range of pitting corrosion with the increasing activation of chloride ions; chloride ions destroy the passivated layer and make its inner surface bare by adsorbing and reacting with the layer on the surface of the alloy. The second phase electrode potential inside turns negative, and together with the aluminum matrix, forms a corrosion micro battery. Its anodic corrosion and dissolution reduce the strength and corrosion resistance of the alloy.