A study of the effects of filler particles on the degradation mechanisms of powder epoxy novolac coating systems under corrosion and erosion

•Mechanism of coating degradation was proposed.•Barrier properties of coatings depend more on the filler amount than particle size.•Coating with increased amount and size of filler provided the best erosion resistance.•Platy shaped filler particles were found to be the best in reinforcing coatings. Electrochemical impedance spectroscopy (EIS) tests were conducted on powder epoxy novolac (PEN) coating systems with different loadings and types of filler particles. The performance of the coatings was examined in an aqueous corrosive environment with a chloride concentration of 2000 ppm, pH of 3.5, temperature of 60 °C, and saturated with carbon dioxide (CO2). The coating’s performance under the influence of grit blast erosion was also studied. Equivalent circuit models were proposed to study the degradation mechanisms of the coating systems under the synergic effect of corrosion and erosion. Coating systems with a low amount of filler particles provided the best protection against corrosion in the testing environment, while systems with an increased amount filler particles provided the best erosion resistance. Platy shaped filler particles were found to be the best in reinforcing coating’s resistance against both corrosion and erosion.