Coatings are often used as a means of protecting steel structures in marine and offshore environments. While the use of coatings is extensive, the assessment of the performance of these coatings can be complicated, particularly if and when the coated steel suffers corrosion damage. Several types of smart coatings have been shown to exhibit properties that allow corrosion to be identified before it can be seen with the naked eye. This would be very advantageous and could potentially result in tremendous savings in time and money when structures undergo routine maintenance. The investigators have examined coatings that incorporate corrosion indicators that change their fluorescent state in the presence of corrosion as a result of changes in pH. The particular corrosion indicators are positive indicators for steel in that they are initially nonfluorescent upon application, but glow over areas of corrosion. In this paper, fluorescence behavior, electrochemical behavior, microscopic evidence, and visual observations of coated steel specimens will be compared based on exposure to saltwater conditions. Some of the challenges associated with the use of these types of coatings will be presented. All of this information is aimed at the development of smart coatings that can reveal the coating and metal condition before it is visible to the naked eye.

INTRODUCTION

The use of smart coatings for corrosion detection in marine and offshore structures would be very desirable. These would be coatings that could somehow reveal damage before it could be seen with the naked eye. To that end, fluorescent coatings have been studied for quite some time, especially for aluminum alloys (Agarwala and Fabiszewski, 1994; Johnson and Agarwala, 1997, Agarwala, 1997, Frankel and Zhang, 1999; Agarwala and Ahmad, 2000; Saidarasamoot et al., 2003). In one of those studies, paints detected changes in acidity and alkalinity by responding when water and air attacked certain metals (Frankel and Zhang, 1999).

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