High temperature corrosion of austenitic stainless steel in simulated rocket combustion gas

The corrosion at elevated temperature of austenitic stainless steel was investigated in simulated rocket combustion gas. The composition of rocket combustion gas was reviewed and selected only dominated species; hydrogen chloride and carbon dioxide. The experiment was set up in laboratory and the environment was prepared in order to observe effect of high temperature corrosion factors (humidity and environmental compositions). CO₂ was supplied by commercial and HCl was prepared by mixing concentrated hydrochloric acid and distilled water to intended concentration. The corrosion testing chamber made by ceramic tube was used for this investigation. The result shows that wet condition tends to accelerate corrosion product formation on stainless steel surface and decrease defensive capability of protective film. The corrosion by hydrogen chloride is relatively more aggressive than carbon dioxide. Hydrogen chloride attacks not only specimen's surface, but internal corrosion also. The protective film was destroyed and chloride ions can pass through such film in order to chemically react with specimen's surface. The corrosion products mainly composed of well-known ferrous oxide (Wütite (FeO) → Magnetite (Fe₃O₄) → Haematite (Fe₂O₃)) and Fe₂₁O₃₂ which resulted from oxy-chlorination reaction. Moreover, because of applied high temperature, precipitation of intermetallic compounds could be detected at the area and chromium depleted zone originated.