Investigating the Effects of Sulfide–Oxide Complex Inclusions and Working Environment on the Corrosion Mechanism of Heat Exchanger Tube

The corrosion behavior of the heat exchanger tube in the acid gas, liquid sulfur and Cl − environment with high temperature is fundamentally clarified. The results revealed that there were some complex (Mn, Ca)S-(Al, Mg)O inclusions in the steel. The corrosion film formed on the tube surface consisted of two layers, which were loose and porous. The tube exhibited the characteristics of localized corrosion, and the pitting corrosion was very serious. Many deep microvoids were distributed at the bottom of pits, and Cl − was enriched in the pits. The dissolution of (Mn, Ca)S triggered the nucleation of pits, and the synergistic effect of (Al, Mg)O, Cl − autocatalytic and sulfur-containing anions acidification promoted the propagation of pits. This eventually resulted in the corrosion failure of the tube.