Prediction of film performance by electrochemical impedance spectroscopy

Corrosion protection performance and lifetime of a sandwich-structured composite film coated on an Mg alloy substrate was experimentally predicted using electrochemical impedance spectroscopy (EIS) after neutral salt spray tests (NSST). The film performance was analyzed by evaluating the relationship between film resistances and phase angles at special frequencies. Moreover, a quantitative basis for estimation of the corrosion protection lifetime of the film was obtained by using an empirical linear relationship between the low frequency impedance modulus and exposure time.