Abstract: The exfoliation corrosion and electrochemical impedance spectroscopy of over-aged LC4 alloy in EXCO solution were studied. During the corrosion process, pitting corrosion occurs at grain boundary first, then corrosion propagates along grain boundary parallel to the alloy surface, the corrosion product accumulates in the grain boundary and lifts the surface.η(MgZn2) phase is well-distributed due to over-aging heat treatment and intergranular corrosion is detered. As a result, the exfoliation degree is superficial and the exfoliation morphology displays as localized blisters. After exfoliation, the impedance spectroscopy is composed of two capacitive arcs, one results from original flat alloy surface, the other from the new interface contacted with the EXCO solution. It is supposed that exfoliation degree can be judged through the analysis of these two capacitive components.
Exfoliation corrosion and electrochemical impedance behavior of LC4 alloy
Abstract:
The exfoliation corrosion and electrochemical impedance spectroscopy of over-aged LC4 alloy in EXCO solution were studied. During the corrosion process, pitting corrosion occurs at grain boundary first, then corrosion propagates along grain boundary parallel to the alloy surface, the corrosion product accumulates in the grain boundary and lifts the surface. η (MgZn 2) phase is well-distributed due to over-aging heat treatment and intergranular corrosion is detered. As a result, the exfoliation degree is superficial and the exfoliation morphology displays as localized blisters. After exfoliation, the impedance spectroscopy is composed of two capacitive arcs, one results from original flat alloy surface, the other from the new interface contacted with the EXCO solution. It is supposed that exfoliation degree can be judged through the analysis of these two capacitive components.
图5 LC4铝合金在EXCO溶液中浸泡不同时间的电化学阻抗谱复平面图 Fig.5 Nyquist plots of impedance of LC4 alloy immersing in EXCO solution for 5 h (a) , 9 h (b) , 23 h (c) and 47 h (d)