To strip the anodizing, I used a bath of drain cleaner. I forget the brand, but it came in a thick ziploc bag. It was a mix of sodium hydroxide (Lye) and potassium hydroxide. I wore rubber gloves - a MUST to do this part. Pour a little drain cleaner on and scrub with a toothbrush QUICKLY. The aluminum gets hot as the dickens real FAST. Scrub, rinse with water to cool off and repeat until the anodizing is gone. After you rinse the last time when your satisfied with the stripping, the aluminum will get a black oxide film on the surface. A quick scrub with Bar Keepers Friend kitchen cleanser removes the oxide layer. Rinse really well and dry. BKF is the only cleanser that works the best because it has oxalic acid in it. This is the key. Other cleansers may work, but will take longer.

Now I’ll sand the cast surfaces between fins and the cutouts to remove the factory CNC machine marks. with 220 grit abrasive and follow with finer grits until I can run a polishing wheel over the surfaces I want polished.