Influence of Residual Cl- on Corrosion Behavior of Hot Rolled Steel in Atmosphereic Envoronment

The influence of residual Cl- on the corrosion behavior of hot rolled steel in atmospheric environment was studied by means of spray dry-wet corrosion test, which was applied to simulate atmospheric corrosion. C3-level of corrosive atmospheric environment was simulated with 4 hours wetting time in each corrosion cycle. The results showed that the atmospheric corrosion rate of hot rolled steel was greatly influenced by Cl- content in industrial circulating water, an exponential relationship between the corrosion rate and Cl- content was exhibited in a certain range. The corrosion rate showed a peak when Cl- content was 60 mg/L, which might be explained by the combined influence of the dissolved chloride ions, and the dissolved oxygen. Reducing Cl- content in industrial circulating water would be an effective way to improve the surface quality of hot rolled steel. When Cl- content reduced from 120 mg/L to 40 mg/L, hot rolled steel exhibited three times capacity of corrosion resistance. For economic perspective, the Cl- content in industrial circulating water at about 40 mg/L would be advisable.