Corrosion Behavior of Rusted Carbon Steel Coated with a Paint Containing Metallic Salt under Wet and Dry Cyclic Condition

Abstract

We have examined the corrosion behavior of a rusted carbon steel coated with a paint containing metallic salt under wet and dry cyclic condition. The rust layer of the carbon steel was already grown in a coastal region of Japan before the coating. It was found that the addition of metallic salt to the coating film decreased the corrosion rate of the coated steel. The X-ray diffraction analysis of the rust layer revealed that the addition of metallic salt resulted in drastic increase of α-FeOOH during the cyclic corrosion test. The rust layer under the coating film containing metallic salt suppressed penetration of Cl^- to the steel surface. Electrochemical analyses indicated that the coating with metallic salt decreased cathodic reduction rate of the rust layer due to the formation of α-FeOOH in the rust layer.