Behaviour of alumina-coated 304L steel in a Waste-to-Energy plant

Pieces of 304L stainless steel, alumina-coated by plasma spraying, were placed during one week at about 1170 K in the furnace of the Waste-to-Energy plant of Limoges, France. The resistance against corrosion was only slightly improved compared to non-coated alloy. The origin of this unsatisfactory result lies in the cracking of the coating that occurred when the pieces were introduced in the furnace, due to the great difference in the Coefficient of Thermal Expansion (CTE) of alumina and 304L steel. However, the plasma-sprayed alumina coatings themselves appear as impervious enough to provide an efficient protection of this alloy against the very corrosive atmosphere of the incinerator.