Study on the structure and corrosion behavior of hot-dipped Zn–6Al–3Mg alloy coating in chlorine-containing environment

Abstract

In this study, the microstructure and corrosion behavior of hot-dipped Zn–6Al–3Mg alloy coating in Cl-containing environment were studied. The results show that there are primary Zn phase, Al-rich phase and ternary eutectic phase in the coating. Electrochemical corrosion occurs due to the formation of micro-electric couples between dendrites and ternary eutectic. The corrosion process can be divided into four stages, including the dissolution of the oxide layer, the corrosion of the coating microstructure, the covering of the corrosion products and the formation of the stable corrosion product layer. In addition, electrochemical tests demonstrated that the active areas on the coating gradually decrease upon extending the corrosion time. The corrosion products protect the coating and improve its corrosion resistance.