Backfill materials - Corrosion
Backfill Materials. The type of backfill used in a groundbed depends on whether the cathodic protection system is sacial or impressed.. Chemical backfills: The chemical backfill used with galvanic anodes provides an environment which is conducive for anode dissolution. A typical mixture is 75% powdered gypsum (calcium sufate), 20% granular bentonite and 5% sodium sulfate.