The operation condition of the air cooler pipeline system of hydrocracker was simulated by a rotary single-phase erosion experimental device. The critical erosion-corrosion properties of 20# steel pipe in sulfur-containing waste water was determined by using the electrochemical method. The micro-morphology of the protective corrosion product film was analyzed by scanning electron microscopy (SEM). Under experimental conditions

the thickness of the protective corrosion product film was 30—40 μm， and the critical flow velocity that caused erosion-corrosion of the protective corrosion product film of 20# steel was about 8.03 m·s-1.