Corrosion of ISG fibers in alkaline solutions

Abstract

AbstractThe corrosion behavior of glass fibers synthesized from the International Simple Glass (ISG) reference ingot, an international High‐Level Waste (HLW) borosilicate glass standard, is reported. Bundles of glass fibers were submerged in 120 mL of four different solutions of initial pH values (pHi) of 9.5, 10.5, 11.5, and 12.5 for static corrosion testing. While all the experiments reached a residual corrosion rate after ~50 days, which remained approximately constant for the duration of the pHi 9.5‐11.5 experiments, the pHi 12.5 experiment underwent a Stage II→III dissolution transition after 57 days. This transition was preceded by a decrease in the Al concentration in solution followed by an increase in B and Si concentration in the leachate. Zeolite NaP2 was observed to form on these fibers via scanning electron microscopy and X‐ray diffraction—the crystallinity of the fibers was estimated to be ~40%‐45% (relative to amorphous component) after the Stage II→III transition. Transmission electron microscopy cross‐sectional imaging of sampled fibers revealed several porous layers on the pHi 9.5‐11.5 samples, and a more aggressive alteration mechanism in the pHi 12.5 fibers. Potential markers that indicate a transition from Stage II→Stage III corrosion are shown to occur based on experimental observations.