Corrosion behaviour of AlN ceramics in LiF-LiCl-LiBr-Li molten salt at 500 °C

Immersion tests of AlN in LiF-LiCl-LiBr-Li salt have been performed at 500 °C to study the corrosion behaviour of AlN. The results show that AlN initially corroded at a higher rate (2⋅10 −5 mg/(mm 2 ⋅h)) during 0−50 h than during 50−300 h (6⋅10 -6 mg/(mm 2 ⋅h)) because the formation of an alumina corrosion layer protected the AlN from further corrosion. The addition of metallic Li at low concentrations (<0.1 wt. %) to the molten salt inhibited the corrosion of AlN by preferentially depleting oxygen impurities, while Li at high concentrations (>0.1 wt. %) accelerated corrosion by reacting with YAG in AlN.