WC-based thermally sprayed coatings are now widely used in a range of industries to improve the mechanical strength of the components, but also enhance the resistance of the substrate to wear and corrosion. High velocity oxygen fuel thermal spraying has been accepted as a pre-eminent technology to deposit composite coatings with high density, superior bond strengths and relatively low decarburization due to the high particle velocities and relatively low particle temperatures induced in the deposition process. Many types of tungsten carbide/metal cermet coatings have been developed by alloying with different chemical elements, in an attempt to enhance corrosion and even erosion-corrosion resistance of coatings produced by HVOF for industrial applications, for example oil and gas industries. In this paper the galvanic series and the erosion-corrosion behaviour of three types of tungsten carbide coatings and three different sealing technologies in simulated oil and gas industry environments are compared. The ultimate goal is to have an understanding of how optimum choice of coating for a given application can be made for applications in the oil and gas industry.