Q. Can anodized aluminium cookware (Kitchen Aid) be kashered for Pesach?

A. Anodization is a process in which by applying an electrical charge on the aluminium vessels, one increases the thickness of the oxide layer on them, thereby making them harder, more durable, and less likely to corrode. This anodized aluminium is less reactive than non-anodized aluminum and far safer to use with food.
Horav Shlomo Miller’s Shlit”a opinion is that although in a sense the metal is oxidized and covered with rust, it does not interfere with the kashering process at all.
It does not compare with Shulchan Aruchs rule (O.H. 451: 3) that before kashering can be effective, all rust should be properly and completely removed. Mainly because no chametz was absorbed before the utensil became rusty so the rust cannot interfere with the removal. The fact that this oxide layer is a desired and needed part and parcel of the utensil itself, does not really matter, since even a factual rusty utensil that absorbed chametz after reaching that stage, can be kashered. We would then say “Kebolo Kach Polto,” in the manner it was absorbed, so it will be expelled.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a.