Oven cleaner and drain cleaner contain the same active chemical, NaOH or sodium hydroxide. In aqueous solution, it easily removes anodizing and will also dissolve bare aluminum if left on. Brownells sells an anodize stripper that is basically NaOH powder. If you follow the instructions, you can safely remove anodized coating with little or no damage to the underlying metal because the chemical concentration is controlled.

WOB