Non-destructive Evaluation of Deteriorated Organic Coated Steels Using Surface Potential Measurement

Abstract

Degradation of organic coated steels has been evaluated by a surface potential measurement which can map electrochemical potential distributions without contact to the specimens. Surface potential measurement of a model specimen to simulate corrosion under an organic coating detected almost the same deteriorated area as the actual defect. A wet and dry cyclic corrosion test under a small droplet of 0.5M NaCl solution was conducted in order to follow the degradation of organic coated steels. The surface potential profile changed after 3 cycles of the corrosion test. The deteriorated area of coating grew with an increase of wet-dry cycles and had expanded to the initial size of the droplet of NaCl solution after 10 cycles of the corrosion test. The surface potential measurement can be a valuable tool for the non-destructive estimation of the degradation of organic coated steels.