The need for automotive coatings to have a proper appearance and aesthetic properties has led to a vast amount of research focused on the study of their weathering performance.1 In this regard, humidity and sunlight are two factors that have been thoroughly investigated. Other environmental factors, such as those that originate from biological sources, have not been investigated systemically. Various biological substances such as bird droppings, tree gums and insect gums can have an impact on the appearance of a car body during its service life. Apart from the lack of knowledge of such a phenomenon with respect to the short-term or long-term effects, the current standard test methods for evaluating resistance to these substances are not sufficient and cannot properly cover all ranges of biological attacks. In general, Arabic gum is considered a universal simulated chemical to study the biological resistance of automotive coatings. This, however, may not represent all biological materials to which coatings are exposed in real-world conditions.2
This article is part of a comprehensive work aimed at studying and characterizing coating degradation caused by various biological substances. Typical defects observed on an automotive clearcoat exposed to bird droppings and pancreatin (the synthetic equivalent) were recorded by a digital camera and are shown in Fig. 1.11