Mechanistic insight into the environmental stress-induced formation and evolution of the micro-defects in deteriorating organic coatings

Abstract

The synergistic effects of corrosion and alternating stresses accelerate the failure of organic coatings during service. However, the influence of alternating stress on coating failure mechanisms remains insufficiently studied. In this study, X-ray diffraction topography (XRT) and scanning electron microscopy (SEM) were employed to analyze the environmental stress-induced formation and evolution of the micro-defects in a deteriorating organic coating. Electrochemical impedance spectroscopy (EIS) was used to investigate how these stress-induced micro-defects affect coating capacitance. The results showed that environmental stresses not only significantly alter the surface morphology of coated specimens but also promote the initiation and growth of both new and pre-existing micro-defects, leading to changes in their distribution. Additionally, applied stresses were found to favor the formation of non-spherical micro-defects more effectively than corrosion stress. Changes in the number and distribution of micro-defects directly influenced coating capacitance, which, in turn, impacted its protective performance. Overall, this study underscores the critical role of environmental stresses in initiating and propagating micro-defects within organic coating protective systems.