Rustyiron
Super Member
TSP mixture. It's a hardware store item.
There are other "recipes" for cleaning only. Just search TSP mixture for aluminum siding.
TSP - Trisodium Phosphate: The Painter's Degreasing Choice
A quality of a paint job depends on using a powerful degreaser, like TSP Trisodium Phosphate, to clean and etch the surface.
www.house-painting-info.com