On the electrochemical and structural behavior of biologically degraded automotive coatings; Part 1: Effect of natural and simulated bird droppings

Environmental factors can potentially deteriorate automotive coatings. These include UV radiation, humidity, hot–cold shocks as well as aggressive chemical compounds. In addition, natural occurring materials such as bird droppings and tree gums are also enable to affect the coatings. The present work aims to study the degradation of an automotive coating system exposed to natural and simulated bird droppings. To this end, structural analysis of samples was studied using FT-IR spectroscopy, optical and atomic force microscopes. Also, the mechanical and electrochemical behaviors of coatings were investigated by DMTA and electrochemical impedance spectroscopy (EIS). It was found that the biological materials significantly affect the mechanical and chemical properties of the coatings, resulting in a decrease in corrosion resistance. A two-time constant semicircle was observed for degraded coatings after a short time as a result of electrolyte diffusion into the coating/metal interface. The behavior of the coatings was then discussed based on the formation of surface defects.