Improvement in the liquid zinc corrosion resistance of high Nb-TiAl alloys by pre-oxidation in a SiO2-powder pack

The influence of pre-oxidation on the liquid zinc corrosion resistance of high Nb-TiAl alloys was investigated. The pre-oxidation was performed by heating the specimens, buried in silica powder and encapsulated in a silica tube under a vacuum of 1.3×10−3 Pa at 950°C for 12 h. Experimental results showed that the preoxidized sample exhibited much higher liquid zinc corrosion resistance than that for the comparative samples. This excellent liquid zinc corrosion resistance was attributed to the formation of high-quality oxide scale during peroxidation. The corrosion of all the samples in liquid zinc was caused by a localized breakdown in the oxide scales. The continuous and dense oxide scale formed during preoxidation substantially may prevent the liquid zinc from diffusing to the substrate, and its good continuity may also reduce the possibility of localized breakdown in the oxide scale.