Abstract: Hydrochloric acid dew point corrosion is a key factor contributing to the failure of overhead vapor line tube bundles in atmospheric distillation towers of refining and petrochemical units. To address this issue, the dew point temperature and pH of the acidic liquid under given operating conditions were determined using Aspen Plus simulations. The immersion corrosion and dew point corrosion test apparatus were constructed, and the corrosion resistance of No.20 carbon steel, 316L stainless steel, and TA2 titanium was evaluated in hydrochloric acid liquid and vapor environments (pH=2.5). Corroded samples were characterized through electrochemical techniques, scanning electron microscopy, X-ray diffraction, and inductively coupled plasma analysis. Experimental results indicate that in the liquid hydrochloric acid phase, the corrosion resistance of the tested materials follows the order: TA2 titanium > 316L stainless steel >No.20 carbon steel. However, in the vapor phase, titanium struggles to passivate and form a protective film in the acidic environmentwith low water content, leading to a revised corrosion resistance ranking as: 316L stainless steel > TA2 titanium >No.20 carbon steel. This study provides valuable insights into the corrosion behavior of materials under both liquid and vapor phase conditions, offering a reference for understanding and mitigating dew point corrosion in the overhead reflux system of atmospheric distillation towers in refining operations.

Key words: hydrochloric acid, dew point corrosion, simulation calculation, electrochemistry, immersion method, No.20 carbon steel, 316L steel, TA2 titanium