Corrosion of press-hardened galvanized steel

Press hardening of hot-dip-galvanized steel sheet yields an innovative product with high strength and reduced weight with drastically increasing industrial importance. This process results in an austenitisation of the steel and a conversion of the 10 mu m Zn layer into a 20 mu m thick coating consisting of zinc saturated a-iron and Gamma-FeZn-phases. A 5-times longer protection is found in cyclic corrosion tests. The mechanism is a combination of the increase of the coating thickness, cathodic protection and the barrier properties of simonkolleite in the corrosion products. Simonkolleite-Zns(OH)(8)Cl-2, hydrozinciteZn(5)(CO3)(2)(OH)(6) and akaganeite-beta-FeOOH were identified as corrosion products by XRD, FT-IR and Raman spectroscopy. (c) 2012 Elsevier Ltd. All rights reserved.