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

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. (c) 2006 Elsevier B.V. All rights reserved.