Atmospheric Corrosion Resistance of Hot-dip Aluminized SUH409L Steel Sheet

A 10-year outdoor exposure test has been carried out to investigate atmospheric corrosion behavior of hot-dip aluminized SUH409L steel sheets in an industrial and a marine environments. Corrosion current density distribution at scribed coating area was measured by scanning vibrating electrode technique (SVET) to study corrosion mechanism. In both environments aluminized SUH409L steel sheets have kept good appearance without red-rust even at bare edges and scribes. Corrosion of aluminized SUH409L steel sheets was slight and the whole surfaces of them including bare edges and scribes were covered with corrosion products mainly consisting of Al, S and O. It was found that these corrosion products adhered to the surfaces suppress the cathodic reaction at bare edges and scribes. It is concluded that the excellent atmospheric corrosion resistance of aluminized SUH409L steel sheets is caused by the sacrificial protection of coatings and the barrier effect of their corrosion products.