Cermet based coatings are being increasingly used to combat erosion–corrosion in oil sands pipelines and pumps where the degradation is caused by a slurry mix of sand particles and aqueous solution. This research assesses the erosion–corrosion resistance of cermet composite coatings obtained by HVOF thermal spraying of microcrystalline and ‘duplex cobalt coated’ near-nanocrystalline WC–17Co feedstock powders. Electrochemical measurements, surface characterization, and the extent of weight loss were studied through an impingement jet system. Results suggest that the erosion–corrosion mechanism in the coatings was dominated by pure erosion in the microcrystalline coating and corrosion-enhanced erosion in the near-nanocrystalline coating.