Comparative Study by Electrochemical Impedance Spectroscopy (EIS) On The Corrosion Resistance of Industrial and Laboratory Zinc Coatings

In this work, corrosion monitoring of Zn-based coatings is investigated through potentiodynamic and electrochemical impedance spectroscopy (EIS) methods. The first part of the study is devoted to galvanised coatings conventionally manufactured in the industry. The second part focuses on the corrosion resistance of a laboratory-made electrolytic coating. For such purpose, the corrosion behaviour is studied in NaCl media under various conditions. The results show that EIS allows to establish the interfacial reactions and the dissolution mechanisms occurring in this media, hence to foresee the protection conferred by these coatings. Moreover, the salted media at different concentrations allow to unambiguously assess the coating quality in terms of porosity. However, others corrosive media can reveal the slowest reaction without having appeal to a very low frenquency scanning. Finally, Zn/NaCl interface is characterised by a specific equivalent circuit giving a similar impedance response.