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.