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The corrosion reaction in the RNH₂ (ethanolamine)–CO₂–H₂S–H₂O system primarily occurs in the high-temperature region of the rich liquid in the desulfurization unit, at temperatures between 90 and 120°C. Corrosion is mainly driven by CO₂, while H₂S has an inhibitory effect on the corrosion caused by CO₂. The main corrosion reaction involves CO₂ dissolving in water to form carbonic acid, which then reacts directly with carbon steel, causing uniform corrosion: Fe + H2CO3 → FeCO3↓ + H2↑. At CO₂ concentrations of 20%–30% and temperatures above 90°C, the corrosion rate can reach 0.76 mm/year; this is the primary mechanism of corrosion. Reactions related to stress corrosion: Ethanolamine reacts irreversibly with CO₂ to form polyamine-based degradation products; at 120°C, CO₂ is released again. The carbonate ions generated continuously in the system, in a basic environment (pH 8–10.5), together with the residual stresses in the equipment, can cause carbonate stress corrosion cracking at the welds. The corrosion products are mainly FeCO₃ and Fe(OH)₂, with almost no iron sulfide present. The special effect of H₂S: When H₂S is present alongside CO₂, the overall corrosion rate of the system is lower than in an environment with only CO₂, and this corrosion rate decreases further as the H₂S concentration increases; H₂S has a significant inhibitory effect on the corrosion caused by CO₂.