Part 4. Phase transformations within the heat-insulating layer of aluminum electrolysis cells

The heat insulating layer of an aluminum electrolyzer is shown to become gradually impregnated with sodium and fluoride compounds. Vermiculite, while subjected to deep dehydration, enters into reaction with electrolysis products, which resulted in damage to the refractory chamotte layer. The saturation with gaseous compounds proceeds along the cleavage plane of vermiculite. Sodium tetrafluoraluminate is shown to form under the electrolyzer’s service conditions. Alongside the pure fluorides, complex fluorides of variable composition have been identified. Fluorides and metallic aluminum have been shown to form by condensation and disproportionation of lower fluorides. Electric corrosion is suggested as a factor affecting the structural integrity of the electrolyzer’s casing.