Superior protection by α-Al2O3/α-LiAlO2 double oxide scales against alkali carbonate corrosion

Ferritic alumina-forming alloys showed high corrosion resistance to molten carbonates by forming a protective alpha-LiAlO2 scale at their surface. In this work, four ferritic alumina-forming alloys were pre-oxidised before exposure to (Li,Na,K)2CO3-melt at 800 degrees C for 1000 h. Only outer transient alumina, such as gamma-alumina, reacts with the melt, forming LiAlO2. At the same time, the innermost alpha-Al2O3 scale remains intact. alpha-Al2O3, as well as alpha-LiAlO2, are slow-growing compressive stress-stabilised oxide scales. Thus, the combined presence of alpha-Al2O3/ alpha-LiAlO2 improves the corrosion protection of materials investigated in this study, compared to non-pre-oxidised ones, by forming a superior double oxide scale.

Automated summary

Ferritic alumina-forming alloys have high corrosion resistance to molten carbonates by forming a protective alpha-LiAlO2 scale on their surface. Pre-oxidized ferritic alumina-forming alloys were exposed to (Li,Na,K)2CO3 melt at 800 degrees C for 1000 hours. Only the outer transient alumina reacts with the melt, forming LiAlO2, while the innermost alpha-Al2O3 scale remains intact. The combined presence of alpha-Al2O3/ alpha-LiAlO2 improves the corrosion protection compared to non-pre-oxidized materials by forming a superior double oxide scale.