Corrosion of uncoated and alumina coated steel X20CrMoV12-1 in H2O–CO2–O2 and air at 600 °C

Future coal power plants will in case of oxyfuel combustion be operated with altered atmospheres. Hence, corrosion attack might become more severe and steels have to be protected. An alumina-sol was used to coat X20CrMoV12-1 (X20) with alumina to test the protection. Testing was performed at 600 °C in flowing H2O–CO2–O2 and static laboratory air for 1000 h. Oxidation under air is minor compared to exposure in oxyfuel atmosphere. In both cases a multilayered oxide (hematite, magnetite, spinel) was formed on uncoated steels. Carburization appeared on uncoated X20 in H2O–CO2–O2. The coating demonstrates a high protection.

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► A 400 nm thick transition alumina layer was able to diminish oxidation.
► The coating prevented carburization.
► Diffusion of alloying elements into the coating lead to formation of mixed oxides.
► Attack on bare and coated X20 at 600 °C was heavier in H2O–CO2–O2 than in air.