A preliminary report on the effects of long-term exposure of LiOH on pure nickel

A 'bread pan' capsule has been designed which allows large numbers of tensile specimens to be simultaneously exposed to molten LiOH, its vapor, and vacuum. Capsules and specimens fabricated from the pure nickel alloy Ni-200 were annealed for 401 hours and 2500 hours at 775 K. Examination of the exposed materials revealed that little outward damage in terms of visible attack, weight change, or loss of room temperature tensile properties occurred. In particular, the mechanical behavior of hydroxide-contaminated alloy was essentially identical to that receiving a simple thermal exposure in vacuum. Examination of the microstructures revealed that LiOH did produce some nonuniform, shallow intergranular corrosion in NI-200; however, the extent of the damage was insufficient to produce weakening or embrittlement.