2019 Volume 59 Issue 10 Pages 1870-1877
Aluminized steel sheets are very resistant to corrosion in the outdoor exposure environment. We evaluated the corrosion behavior of aluminized steel sheets with a Type 1 coating containing approximately 10% Si and a Type 2 coating not containing Si in a 50-year outdoor exposure test. Both specimens had strong perforation resistance, but those with Type 2 coating exhibited excellent perforation resistance. Type 2 aluminized steel sheets are known as a superior corrosion resistant materials compared to Type 1 aluminized steel sheets due to their thicker intermediate layer and higher coating weight. The Type 2 aluminized steel sheets in this exposure test included 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 the steel substrate and the Fe2Al5 phase in an artificial rain environment. As a result, this layer provided sacrificial corrosion protection for the steel substrate, and was the reason why the specimens with Type 2 coating exhibited better perforation resistance than those with Type 1 coating.