Stages and mechanism of Q420B hot-dip galvanized steel corrosion in simulated dry/wet coastal atmosphere

The corrosion degradation behavior and mechanism evolution of Q420B hot-dip galvanized steel in simulated coastal atmosphere was investigated. The stages of galvanized steel degradation were redefined based on its corrosion kinetics under cyclic dry/wet coastal atmosphere. It was observed that the corrosion rates of the eta, zeta, and delta sub-layers decrease sequentially, attributed to differences in their corrosion potentials and the barrier effect of the corrosion product layers. Furthermore, the findings reveal that the thinning of the galvanized layer under corrosion product coverage follows a linear function, with the alloy layer accounting for approximately 90 % of the total coating lifespan.