Corrosion behavior of aluminized steel sheets in 50-year outdoor exposure test

Abstract

Aluminized steel sheets are very resistant to corrosion in the outdoor exposure environment. We evaluated the corrosion behavior of aluminized steel sheets with a Type1 coating containing around 10%Si but also a Type2 coating not containing Si in a 50-year outdoor exposure test. Both specimens had strong perforation resistance, but those with Type2 coating had superior perforation resistance. The Type2 aluminized steel sheets had two sublayers composed of Fe2Al5 and FeAl2 as the intermediate layer between the aluminized layer and the steel substrate. The FeAl2 phase has less noble potential than steel substrate and the Fe2Al5 phase in an artificial rain water environment. As a result, this layer provided sacrificial corrosion protection for the steel substrate. That was why the specimens with the Type2 coating had better perforation resistance than those with Type1 coating.