Characterization by acoustic emission and electrochemical impedance spectroscopy of the cathodic disbonding of Zn coating

Galvanized steel has been tested in a synthetic sea water solution under different cathodic overprotection conditions. The generated hydrogen flux caused the damage of the metal–zinc interface and led to a progressive coating detachment.Scanning electron microscopy, electrochemical impedance spectroscopy and acoustic emission technique were used to characterize the damage chronology under different cathodic potentials.A damage mechanism was proposed and the acoustic signature related to the coating degradation was statistically identified using clustering techniques.