Correlation between active/inactive (Ca, Mg, Al)-Ox-Sy inclusions and localised marine corrosion of EH36 steels

Abstract

The correlation between (Ca, Mg, Al)-Ox-Sy inclusions and localised marine corrosion of EH36 steels was investigated. According to their ability to induce localised corrosion, the inclusions were categorised as ‘active’ or ‘inactive’, and the main difference between them was the ratio of CaO/Al2O3. The residual stress at the active inclusion/matrix interface was higher than the yield strength of the steel; therefore, a local plastic deformation region was preferentially formed, triggering localised corrosion initiation. Moreover, the occluded cell accelerated the localised corrosion propagation, and finally the dissolution of the inclusions and the matrix resulted in a stable pit.

Keywords

• Low-alloy steel
• SEM
• Inclusion
• Anodic dissolution
• Pitting corrosion