Corrosion behavior of HVOF sprayed WC-10Co4Cr coatings in the simulated seawater drilling fluid under the high pressure

•WC-10Co4Cr coatings with bimodal structures have superior properties than conventional structures.•WC-10Co4Cr coatings have a better corrosion resistance than substrate.•The bimodal coatings have better corrosion resistance than conventional coatings.•The micro-galvanic corrosion is the primary corrosion mechanism of the coatings, and the crevice corrosion also exists.