Fluorescent materials have been previously identified that fluoresce upon oxidation or upon complexation with metal ions or metal oxides on selected surfaces. These materials include fluorescein, oxine, morin, and some Schiff bases. The present work describes further work on incorporating these materials into coatings. Fluorescent measurements including spectroscopy and UV photography were used to follow changes in these coatings with time. Another additive to coatings that inhibits corrosion was also tested and results are reported. The overall objective would be to produce a smart coating that would detect corrosion, inhibit corrosion and even provide a release agent to help remove coating for easy retreatment.
Corrosion has become an expensive and hazardous problem. It is estimated to be a $100 Billion problem overall and for Navy aircraft the cost is at least $1.2 Billion. The concept of a smart coating could result in savings of 20-30°/0 of this cost by reducing maintenance time and treating only corroded areas. The smart coating is illustrated in Figure 1 and incorporates three substances into coatings. The first is a corrosion detecting substance, the second is a corrosion inhibitor and the third is a coating release substance to facilitate retreatment of corroded areas. Corrosion is detected by scanning large surfaces with UV light and marking or mapping out spots that have become fluorescent due to oxidation. The fluorescence could be due to a substance that becomes fluorescent either when oxidized or when combined with oxidation products. The fluorescence should be matched to the surface material so that oxidation rates are comparable and the rate of corrosion on the surface is being monitored. The second part of this smart coating is the release of a corrosion inhibitor incorporated into the coating. This should be a slow time release due to the inhibitor either encapsulated or absorbed into an inert support. The final component in the smart coating is a coating release material, that when activated, breaks the bonding of the coating to the alloy surface. This would facilitate the removal of coating, repair of corroded areas and the repainting of these areas.
