Automotive clearcoat damage due to oviposition of dragonflies

Automotive industries are increasingly interested in learning how to prolon g the clearcoat resin lifetime and avoid its thermal, photochemical, and ch emical degradation. While chemical degradation by acid rain has been well k nown since the beginning of the decade and the subject of many studies, che mical degradation of the automotive clearcoat by living organisms (except b y bird droppings) is a newly recognized problem. In this work, we report th e chemical degradation of the automotive clearcoat caused by oviposition of dragonflies. These insects, very common in Brazil, are attracted by the re flecting surface of cars exposed in the sun and lay eggs on them. We observ ed that the eggs, at the high temperatures (50-92 degrees C) of the car sur face, can cause damage similar to that of acid rain. In experiments on resi n-coated plates, we excluded the involvement of H2O2-or hydroquinone-derive d radicals, of enzyme-catalyzed hydrolysis, and of photosensitizer-induced damage. The damage was very similar, however, to that produced by the sulfu r-containing amino acids, cysteine and cystine, at high temperature. Due to this similarity, and because the eggs are rich in sulfur amino acids, we p ropose a mechanism involving cysteine and cystine residues in the clearcoat damage. (C) 2000 John Wiley & Sons, Inc.