Long-term deterioration mechanism of hot-dip aluminum coating exposed to a coastal-atmospheric environment

This study focused on the long-term corrosion mechanism of hot-dip aluminum (HDA) coating applied to a steel bridge exposed to a coastal-atmospheric environment. Aging HDA samples were taken from the actual bridge, and the corrosion product composition and morphology of the deterioration stages were investigated. The localized environmental assessment indicated that the surface orientation of the structural members led to a significant difference in salt accumulation and corrosion rate, with the most important influence being the rain-washing effect. Besides, open circuit potential, critical pitting potential, and aging sequence of different metallic phases were clarified. In addition, the long-term deterioration mechanism and pitting growth kinetics of aging HDA were speculated and verified with electrochemistry and elemental analysis.