► The coatings exhibit higher hardness and E–C resistance than 304 stainless steel. ► E–C rate increases with flow velocity, particle size and sand content. ► E–C rate depends on amorphous phase contents, porosities and hardness. ► E–C process is mechanically dominated and attack arises from coatings defects. ► The coatings may be good candidates to solve E–C problems of marine pumps. Corrosion and slurry erosion–corrosion (E–C) behaviour of FeCrMoMnWBCSi amorphous metallic coatings (AMCs) compared with 304 stainless steel was investigated by static electrochemical measurements and weight loss tests under rotating conditions in simulated seawater. E–C rates of the AMCs increased with flow velocity, particle size, sand content and NaCl concentration. The AMCs are preferentially attacked at coating defects. The superior E–C resistance of AMCs can be attributed to the high micro-hardness, alloying elements and amorphous microstructure. The AMCs with better slurry E–C resistance may be good candidates to solve the E–C problems of marine pumps in sand-containing seawater.