Previous investigations into the erosive–corrosive wear of metals in aqueous conditions have concluded that the process is best described by discrete wear regimes. Such regimes identify the dominant wear process that is causing wastage of the target material. Primarily, the regimes are categorized by the dominating electrochemical process, whether this is dissolution, passivation, or immunity. These are then separated further depending on how erosion contributes to the overall material loss. To help visualise the erosion–corrosion behaviour of different metals, wear maps have been developed, which show the various wear regimes as a function of applied potential and impinging particle velocity. Because of the large number of independent and interdependent variables in the mathematical model of the erosion–corrosion mechanism, the wear map has become a valuable tool in predicting the performance of a pure metal, when subjected to impinging aqueous slurry. Until now, erosion–corrosion maps have had limited prospects for commercial use because they only exist for pure metals. This paper proposes a method for the generation of wear maps for stainless steel. Erosion–corrosion regime and wastage maps are then constructed, for the iron–chromium–nickel system, based on this method. These maps are further developed by exploring the effect of increasing particle concentration. To demonstrate how these wear maps are utilised in a practical situation, a hypothetical problem is posed, based on a tidal power generator, and the erosion–corrosion model applied accordingly. Following this, material selection maps are presented and discussed. These superimposed wastage maps provide an easy method for selecting the choice material for any given range of environmental conditions. Finally, the model used to construct the maps is discussed and thoughts for future work outlined.