The quickest and easiest way I've found to remove anodized finishes is to use lye solution. I've used it to remove anodizing from Ruger revolver grip frames and ejector housings down to base metal before final polishing.
Common household lye (sodium hydroxide) in the form of Draino brand drain cleaning product. It's in the form of lye crystals with bits of aluminum chips to make it "bubble" when clearing drains.
You gotta be CAREFUL using this stuff!! Wear eye and face protection (goggles, glasses, face shield), rubber gloves, and protective clothing. Lye will eat skin, organic materials, and can easily blind you. Work near a source or running tap water for quick rinsing and disposal of used lye.
Add lye crystals to a few cups of water in a stainless cooking pan.
Don't use plastics or rubber.... the lye will eat the container!
The solution will get hot as you mix the lye crystals (exothermic).
The concentration is not critcal. Use say, 1/2 can for about a quart of water.
Using wire coat hangers, dangle the part in the solution, and move it around. Be prepared for considerable bubbling and foaming. Depending on the concentration, the temperature, and the amount of anodizing, the lye will eat through to bare metal within a minute or two. Remove the part, rinse off in clean water, and examine. If there are any missed parts, re-immerse briefly.
Dispose of solution just like you would used drain cleaner. You can safely pour it down the drain.
CAUTION: The ly may be harmful for septic tanks (kill the bacteria) and cause drainage problems.
