Corrosion deterioration characteristics of Sn-bearing steel and its applicability on steel bridges

The steel with a small amount of tin (Sn), that is, Sn-bearing steel was newly developed by noting the effect of adding such kind of trace alloy element for improving the corrosion resistance of steel. In order to investigate the corrosion deterioration characteristics around paint coating defect of the Sn-bearing steel, accelerated exposure test was performed. After the test, the appearance and surface shape of paint coated Sn-bearing steel were examined for evaluating the degree of deterioration. The corrosion deterioration was evaluated by focusing on the blister of paint coating around the initial defect scribed in X shape (namely, cross-scribe defect). The blister areas from the cross scribe paint defect of the Sn-bearing steel was respectively 95 % in A-type coating and 43 % in C-type coating of those of the SM490 steel at 2200 cycles. For C-type coating, the use of Sn- bearing steel to bridges has the possibility to prolong the life span of paint coating by around l5 %.