Abstract: Corrosion of dehydrogenation exhaust system was mainly concentrated in inlet pipes of cooler, casing head and outlet of cooler in styrene unit, with typical local corrosion morphology by CO2, such as pit corrosion, trench corrosion and platform corrosion. The corrosion mechanism was the galvanic corrosion caused by the different coverage of FeCO3 corrosion products on the metal surface. The operation results showed that the corrosion of CO2 was slight toward austenitic stainless steel equipment and pipeline, but serious for carbon steel equipment and pipeline and that the system process, temperature, material and pipeline structure provide the environment condition and promotion for the occurrence and development of carbon dioxide corrosion. In view of the process flow and corrosive environment of the system, the solutions of replacing the material and adding neutralizing corrosion inhibitor was put forward and the good results of anti-corrosion achieved.

Key words: styrene, dehydrogenation exhaust, CO2, corrosion, protection