Coatings for Early Corrosion Detection

Corrosion of metal alloys can sometimes be detected based on coatings that incorporate corrosion indicators. The indicators may change color or fluorescence depending on pH or they may change fluorescence based on changes in oxidation state. The investigators have examined aluminum alloys and steels and used positive or negative indicators. The positive indicators for steel are initially non-fluorescent upon application, but glow over areas of corrosion. While microscopic and electrochemical results have demonstrated some success in early corrosion detection in aluminum alloy specimens, several challenging issues were noted for steel alloys. For example, coating degradation was observed by EIS as a function of exposure to saltwater. Moreover, in some cases, increases in fluorescence were also observed as a function of exposure. However, these incidents did not occur simultaneously and the fluorescent locations changed with time and did not grow with time. This paper will explore some of the possible reasons for this behavior.