The effect of oxide layer thickness and morphology on KCl-induced corrosion at elevated temperatures

The increasing power demand combined with the growing interest in more complex fuels such as biomass and waste create continuously challenges for material designers. Instead of preventing corrosion with expensive high-alloyed materials, possibilities such as oxide layer manipulation/passivation should be studied more thoroughly to find alternative and more cost-efficient ways to design materials with improved capability to resist corrosion.The corrosion resistance of three pre-oxidized commercial steels; the low alloy ferritic 10CrMo9-10, the Nb-stabilized austenitic AISI347, and the high alloy austenitic Sanicro 28, was compared in tube furnace exposures in the presence of potassium chloride (KCl) for 168 hours at 550°C. Prior to the exposures, the samples were pre-oxidized for either 5 or 24 hours at 500°C. In terms of oxidation in the presence of a corrosive salt, the material’s ability to resist corrosion depended on the pre-oxidation conditions. The layer structure varied from steel to steel, resulting in a porous yet more continuous and better adhered oxide layers on the austenitic steels, contrary to a multi-layered oxide formed on the ferritic steel.