Corrosion Evaluation and Material Selection of the Overhead System of H₂S Stripping Tower in Hydrogenation Unit

The operating condition of H₂S stripping tower was simulation, the general corrosion, pitting corrosion and stress corrosion cracking sensitivity of 20^#, 304L, 321 and 316L in wet H₂S environment were evaluated by immersion corrosion test, potentiostatic anodic polarization method and U-bent specimen test. The results showed that the corrosion resistance of 20^# steel was poor, and hydrogen blistering was easy to occure at low temperature. 304L, 321, 316L austenitic stainless steels and 2205 duplex steel had a low corrosion rate and much better corrosion resistance. The pitting resistance of 304L and 321 stainless steels was a bit poor compared with 316L and 2205 steels, and honeycomb localized corrosion caused by slight pitting appeared. The existence of H₂S observably enhanced the pitting sensitivity of austenitic stainless steels in the environment containing Cl^-. The welding samples of 304L, 321 and 316L stainless steels had a good resistance to stress corrosion cracking.