I m not even sure there s a way to do it ... Some of my alu parts have some pitting. I can polish it on surface, but unless removing a lot ( too much ) of material, there s still a dark oxydation . I don t really mind the pitting , it s a part of history, but I ve never been able to find a way to remove the dark. It s easy with steel , using electrolysis or Evapo Rust, but what about alu ? There may be a chemical product ... Acid, caustic, voodoo ritual, whatever I DON T want to use mechanical action, it would damage too much. I d just like "clean pitting" Thanks. Picture of a outboard engine, I didn t have one of the car parts, sorry.
Citric acid (which is lemon juice) is being used to save the wreck of the WWII Dornier bomber which has been on the seabed, and is mostly made of aluminium alloy. I dont know if that will apply to your situation, but would be worth trying a little area to see if it works.
The dark spots you see is probably not aluminum oxide, it is either clear or white. Wash it good with a detergent and water and see what you can get off. The detergent is alkaline and will both clean and attack the aluminum removing the oxides and some of the aluminum. You can use a non metal brush to help get down in the pits to remove what is there. Don't use anything that is a very strong caustic solution because it will eat the aluminum.
Is it polishing compound in pits? Use hot water. Either dishwasher if small or hot water pressure washer.
on a out-of the way/sight spot try easy off oven cleaner. it will take the anodizing of,maybe it will help with this. good luck and let us know what you find works.
Oven cleaner is extremely basic (lye is the main ingredient). It may darken your aluminum. I have had good results with Napa Aluminum Brightener - apply for 30-40 seconds and wash off, it will leave a dark slimy film on the aluminum but will scrub off without much effort. Here's a vintage inverse cylinder lubricator I cleaned up with it; Before After
I thought about oven cleaner and other lye based products, but yes it will darken. Same thing for sulfuric acid IIRC ( from car battery ) I m aware there s still some compound on the picture. It was not the point. This is easy to remove. I ll try citric acid. gwhite : your part is clean, but has still dark spots. That s exactly what I want to remove. BTW it s a really nice object ! Thanks all for the suggestions.
Keep us posted, I'd like to get rid of the dark spots too - but am too afraid to try anything abrasive.
Use chrome wire wheel cleaner - mequiar's or eagle 1 - has muriatic acid in it - will turn the aluminum to new look