Analysis of corrosion of hot-rolled X70 steel plate during storage

In this work, analysis was performed to investigate the reason resulting in corrosion, especially pitting corrosion, of a stock of hot-rolled X70 steel plates after 4 months of storage in a warehouse. Results demonstrated that corrosion and pitting corrosion of X70 steel plate during storage is attributed to the remnant and concentration of cooling water on the top surface of the plate. Pitting corrosion occurs locally at defects on surface deposit that is generated during corrosion of the steel. The small anode vs. big cathode geometry enhances the pitting corrosion process. Chloride ions enter the pits to maintain the charge-neutrality, while ferrous ions that are generated during corrosion diffuse out of the pits to result in corrosion product layer at pit mouth.