The Kinetics of the Coherent Stage of Hydroxide Corrosion on Li ₂ O-Covered LiH

The capability to model LiOH growth on vacuum-baked LiH is a necessary precursor to making kinetic predictions of undesirable hydrogen outgassing from corroded LiH materials when placed in sealed-system applications. In this work, LiH samples with initial LiOH surface corrosion layers less than 1.1 μm were outgassed by vacuum baking at high temperature to convert LiOH to Li2O. Diffuse-reflectance infrared Fourier transform (DRIFT) spectroscopy was used to measure the subsequent LiOH regrowth during exposure to 25–375 ppm of H2O vapor at room temperature. Logarithmic kinetics best model the growth of this coherent hydroxide corrosion layer (up to 1.5 μm) on previously vacuum-baked LiH samples. The logarithmic kinetics are attributed to the dissociation of H2O on the corrosion layer and the establishment of a H+/OH– electric field across the thickening LiOH corrosion layer. A time-dependent model of LiOH corrosion growth as a function of both initial LiOH thickness before vacuum baking and moisture partial pressures during re-exposure was developed to help researchers better assess the unwanted hydrogen outgassing potential from LiH/LiD materials.