Exfoliation corrosion of Al–Zn–Mg–Cu–Zr alloy containing Sc examined by electrochemical impedance spectroscopy

Abstract The exfoliation corrosion behavior of an Al–Zn–Mg–Cu–Zr alloy containing Sc artificially aged at 120 °C for 24 h is studied by macroscopic observation techniques and electrochemical impedance spectroscopy (EIS) measurements. After 48 h immersion, the blisters start bursting and delamination initiates, along with the appearance of two time constants in the impedance diagrams. According to the simulation by equivalent circuit, the corrosion rate decreases sharply and then reaches a steady state, which is due to the change of the solution pH and oxide layer thickness, as well as the accumulation of corrosion products.