This paper describes a study case of the erosion-corrosion wear for ball—valve pump, which works in a crude petroleum fluid. The experimental results were used to identify the optimal material for ball and seat of valve pump. The synergic effect of erosion and corrosion rate was observed for carbide and ceramic composites. The relations for the erosion rate and corrosion can be used to construct wear maps for ball and seat materials working in petroleum fluids.