Hot Corrosion Behavior of Ti45Al8.5Nb Alloy: Effect of Anodization and Pre-oxidation

The hot corrosion behavior of Ti45Al8.5Nb alloy was studied in the salt of Na2SO4 and/or NaCl at 700 °C. To improve the hot corrosion resistance, Ti45Al8.5Nb alloy was anodized in fluorine-containing solution and pre-oxidized in air. Results showed that the combination of anodization and pre-oxidation can efficiently enhance the hot corrosion resistance of Ti45Al8.5Nb alloy contaminated with Na2SO4 or Na2SO4 + NaCl deposits. This is because anodization and pre-oxidation result in the formation of compact Al2O3 layer which can act as a diffusion barrier to prevent sulfur, chlorine, and oxygen from attacking the alloy, therefore providing good resistance against hot corrosion. When exposed to NaCl deposit, however, no obvious improvement was achieved on the hot corrosion behavior no matter the alloy was anodized or further pre-oxidized in air.