Degradation of epoxy coatings exposed to impingement flow

Abstract

Organic coatings are widely used for the corrosion protection of metals. Despite a wide range of work on the degradation of organic coatings, few studies have contributed to understand the influence of the fluid flow on the degradation of organic coatings. In this study, an epoxy coating is exposed to a vertical impingement flow of a 3.5 wt% NaCl solution with a variety of flow rates. The coating degradation is monitored by electrochemical impedance spectroscopy (EIS). Equivalent circuit models are employed to interpret the EIS spectra. Atomic force microscopy (AFM) was employed to study the influence of fluid flow on the surface topology of the coating samples. We found that the coating’s barrier property deteriorates more drastically when exposed to higher flow rates for impingement flow. Coating thickness and surface roughness are significantly affected by the fluid shear and the flow rate. It is concluded that the impingement flow substantially impacts the barrier properties of epoxy coatings owing to its influence on the electrochemical properties of the coating layers and the fluid shear it creates on the coating surface.