Koch Chemie Reactive Rust Remover Rrr is the pH 7.5 iron / fallout / rust remover from the German manufacturer. Additives help clean and also keep the product from drying out quickly on the surface (a constant thing to watch with any iron fallout remover).
Rrr sprays on like a gel, will dwell for around 5 minutes depending on environment, reacts purple, and rinses off relatively easily with pressure.
As with any unfinished metal like polished aluminum, you need to be careful as it WILL mark the surface. Use on such surfaces if the presence of brake dust or fallout REQUIRES you to decon the surface before you polish the area. ONLY.