ABSTRACT The corrosion failure of heat exchanger E2111 in sour water vaporization system of coal chemical plant was studied. The Aspen Plus software was used to analyze and calculate the corrosive gas composition and equilibrium distribution law of ammonia vapor stripping tower. The results show that the main corrosive gas are CO 2 , NH 3 , H 2 S, and H 2 O in the temperature range of 135.1°C–108.6°C in the E2111. The dew‐point temperature of the water is 134.4°C, meaning that the H 2 O(g) changes into H 2 O(l). With the temperature decreasing, the volume fraction of H 2 O(l) increases, and the corrosive gases are dissolved in the water causing scouring corrosion of the pipe wall. In the E2111, H 2 S and NH 3 partial pressure values can not form the common NH 4 HS salt, which causes a large number of pipeline failures. But the process generated NH 2 COONH 4 salt, which is regarded as the main source of corrosive medium in this case. After corrosion characterization test, it was found that the composition of the residual corrosion products was consistent with calculation results, and the corrosion prior occurred on the outer wall of the tube, that is, shell side.