The work aims to study the corrosion resistance of hydrofining heat exchangers tubes after improved hot-dipping aluminum treatment in different ammonium chloride environments, and analyze the corrosion resistance mechanism. 20# steel, 15CrMo steel and 321 stainless steel were treated by improved hot-dipping aluminum technology. The thickness, structure and composition of coatings were analyzed by optical microscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). The corrosion resistance in ammonium chloride of hot-dipped aluminum coating was evaluated by corrosion test under wet ammonium chloride and simulated service condition test of high temperature and high pressure autoclave. The obtained hot-dipped aluminum coatings on 20 # steel, 15CrMo steel and 321 stainless steel had no surface defects, and the thickness were all over 0.080 mm. The coating structure was mainly composed of pure Al layer, Fe-Al alloy layer and a small amount of Al2O3. Under the condition of wet ammonium chloride, the corrosion rates of 20# steel and 15CrMo steel increased obviously with the increasing temperature. The corrosion rates reached 21.6 mm/a and 19.9 mm/a respectively at 80 ℃. For 321 stainless steel, the pitting corrosion was obvious. After hot-dipped aluminum treatment, the surface of three samples had no corrosion found in the same medium for one month, and the hot-dipped aluminum coatings after simulated conditions in high temperature and high pressure autoclave did not have corrosion, either. The quality of hot-dipped aluminum coating of 20# steel, 15CrMo steel and 321 stainless steel hydrofining heat exchangers tubes by improved technology meets the national standards. These results of corrosion test under wet ammonium chloride and simulated service condition test of high temperature and high pressure autoclave confirm that the hot-dipped aluminum coating has good anti-corrosion performance in the service environment of ammonium chloride.