Further Corrosion Behaviors of Low Carbon Bainitic Steel in the Environment Containing Cl- after the Rust Layer Damaged

Electrochemical measurement, metallographic observation and x-ray diffraction analysis were employed to investigate the further corrosion behaviors of low carbon bainitic steel in the environment containing Cl- after its original rust layers had been damaged on different ways. It was found the damnification of rust layers on the low carbon bainitic steel (LCBS) and steels utilized as contrasts, i.e. low carbon ferrite steel (LCS) and a commercial weathering steel 09CUPCrNi (09Cu), could be rapidly self-repaired in the further corrosion process. When damnification degree and further corrosion time were same, the resistance of rust layers and the repair degree of damnification of the low carbon bainitic steel were higher than those of contrasts. The repair ratio of inside damnification is always higher than that of crossed damnification, due to faster formation of rust layer at damaged site, in which NaCl aqueous solution is reserved after dropping. Alloy elements such as Cu and Cr obviously enhance protection of rust layer newly formed at damaged sites. These results indicate that the alloy element content in weathering steel is not enough to improve obviously corrosion resistance of steel matrix, while it is sufficient to enhance protection of rust layer.