Mapping erosion–corrosion of WC/Co–Cr based composite coatings: Particle velocity and applied potential effects

Abstract

In studies of erosion–corrosion of composite based coatings, there have been few attempts to map the mechanisms of the erosion–corrosion process. This is despite the fact cermet-based coatings are being increasingly used to combat erosion on pipelines and pumps where the degradation is caused by a combination of sand particles and seawater. In addition, the interactions between the processes of erosion and corrosion have only been evaluated for a limited range of conditions, despite the fact that erosion–corrosion occurs over a wide range of variables in practice. In this study, the effects of velocity, particle concentration and potential were evaluated for a WC/Co–Cr based coating. The extent of wastage was assessed using scanning electron microscopy and weight loss techniques. Mechanisms of erosion–corrosion were identified from the results. The results were used to generate erosion–corrosion mechanism maps for the coated and uncoated specimens. Velocity/potential maps were constructed showing the transitions between the erosion–corrosion regimes as a function of these parameters. The extent of synergy was also superimposed on such maps, showing the conditions where synergistic effects were likely to be at a minimum for the main process parameters.