Corrosion behaviour of galvanized steel studied by electrochemical microprobes applied on low-angle cross sections

The combined use of the microcapillary cell (MEC) and scanning vibrating electrode technique (SVET) and low angle cross sections was employed to elucidate the role of each coating region on the protection of the cut-edge corrosion of galvanized steels. Different compounds are involved in the blocking action of the corrosion products: Zincite (ZnO) on the steel substrate, hydrozincite (Zn-5(OH)(6)(CO3)(2)) at the coating/steel interface, and Simonkolleite (Zn-5(OH)(5)Cl-2) and ZnO on the different coating regions in different proportions. The coating surface is also active at the initial stage and during long-term protection and thus, must be considered in experimental simulation of the cut-edge corrosion.