You searched for ACIDPROOF
1. acidproof
Syntax: cast acidproof <object>
This spell adds permanent protection against acid‑based attacks. Items not
protected against acid‑based attacks are vulnerable to decay in armor
quality. Blessed items have less of a chance to be affected by such
attacks. Containers and quest items are immune to acid.
Acid can destroy corpses, food, trash, armor, clothing, staves, wands,
scrolls, potions, pills, and drink containers.
If a piece of armor wasn't acidproof and the armor quality was damaged by
acid, the armor can be repaired with 'quest repair <item>' at a questmaster
for a price.