Always use nitrile gloves and goggles at minimum when working with muriatic or Hydroxide-lye. I wouldn’t recommend caustic on aluminum at all it can react with aluminum and cause cancers to develop….on the metal. Either like the others have said don’t leave it on the the equipment. Where i normally see acid used is when there is transfer metal (normally aluminum) someone is trying to clear out not on the entire cylinder wall.Most sensible answer yet!