The erosion-corrosion resistance of high alloy stainless steel UNS S32654 and standard stainless steel UNS S31603 has been assessed under liquid-solid impingement conditions. The electrochemical characteristics of the two stainless steels have been examined via free corrosion potential measurements, anodic polarisation, linear polarisation and potentiostatic control in erosion-corrosion.It has been shown in this paper that high alloy stainless steel UNS S32654 exhibits better corrosion and erosion-corrosion performance than lower grade alloy UNS S31603. A general linear relationship between two electrochemical parameters (E c o r r and R p ) has been shown in this study. A critical solid loading between 60 and 100mg/l, at which there is a transition from corrosion to erosion-corrosion for the two stainless steels under different conditions, has been determined.