Hot corrosion and protection of Ti2AlC against Na2SO4 salt in air

The hot corrosion behavior of Na2SO4-coated Ti2AlC was investigated by means of thermogravimetric analysis, X-ray diffraction, and scanning electron microscopy/energy dispersive spectroscopy. This carbide displays good hot corrosion resistance below the melting point of Na2SO4 while the corrosion attacks become virulent when the salt is molten. A protectively continuous Al2O3 layer forms and imparts good corrosion resistance, and consequently, the corrosion kinetics is generally parabolic at 850 °C. However, porous oxide scales fail to protect the Ti2AlC substrate at 900 and 1000 °C. The segregation of sulfur at the corrosion scale/substrate interface accelerates the corrosion of Ti2AlC. Furthermore, a convenient and efficient pre-oxidation method is proposed to improve the high-temperature hot corrosion resistance of Ti2AlC. An Al2O3 scale formed during pre-oxidation treatment can remarkably restrain the infiltration of the molten salt into the substrate and prevent the substrate from severe corrosion attacks.