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.