Comparative studies on the initial stage of arc-sprayed and zinc-rich powder coatings in sulfur-rich environment

A comparative study of the electric arc-sprayed (AS) and zinc-rich powder (ZRP) coatings, was performed in sulfur-rich environment involving atmospheric corrosion test and cyclic wet-dry test. The surface morphologies and characterization of corrosion products were investigated using SEM/EDS, XRD and EPMA techniques. The anti-corrosion properties of both coatings were compared by taking electrochemical measurements. The results revealed that the corrosion resistance of the ZRP coating was higher than that of AS one in the experimental test. A general sequence for the evolution of corrosion products on zinc coatings in sulfur-rich environment was proposed: Zn → ZnO/Zn(OH)2/ZnSO4 → Zn5(CO3)2(OH)6 → Zn4SO4(OH)6/ZnSO4⋅7H2O.