High temperature corrosion testing of engineering alloys in contact with molten chlorides

A test method is proposed for high temperature corrosion testing of engineering alloys in contact with molten chlorides. The proposed test method successfully generated rapid corrosion and allowed analysis of the corrosion mechanism and relative ranking of materials. The majority of the attack occurred in the vicinity of the salt-air interface, demonstrating that the bulk of the attack will occur in 'splash zones' in a similar manner to that observed in aqueous corrosion. Alloy 625 performed the best but all materials were severely attacked by molten LiCl-KCl. Alloy 625 corroded by a mixture of pitting and intergranular attack in this environment, with formation of a thinner porous two-layer scale layer containing primarily nickel and molybdenum oxides with some niobium particles. Corrosion was heaviest near the salt-air interface, which shifted over time, but the corrosion rates were similar above and below the salt surface. 310 stainless steel, alloy 625 and P91 corroded heavily in this model molten chloride environment at this temperature. The proposed test method displayed rapid corrosion in a short period of time and allowed detailed studies of the corrosion mechanism to be made.