Exposure experiments of some metallic materials were carried out in the fluidized bed low-BTU coal gasification pilot-plant of Coal Mining Research Center. The test materials contains a carbon steel, chromium-molybdenum steels, stainless steels and superalloys along with the aluminum- or chromium-coated materials. These materials were attacked mainly with oxidation and sulfidation and the major factor of corrosion was sulfidation. It was found that the corrosion behavior of alloys was strongly dependent on the chromium content in the alloys. It was also found that alloys with lower chromium contents such as 2.25Cr-1Mo steel and SUS410 are hardly applicable for the coal gas atmosphere. SUS347 gave comparatively good results rather than the other austenitic stainless steels containing 18% chromium.
In superalloys the scaling losses of Hastelloy X, 50Ni-50Cr and S-816 were extremely low. Then it can be concluded that the chromiun content in the alloys should be increased more than 20% in order to give a good corrosion performance in the coal gas environment. It was also revealed that the chromium-coated material resulted in a high corrosion resistance, whilst the aluminum-coated alloys did not show sufficient resistance to high temperature corrosion. Aluminum as an alloying element also had little effect for the increased corrosion resistance.
