WM Barr GKPA30220 Phosphoric Prep & Etch, Gallon Klean-Strip Phosphoric Prep & Etch does the job of three products: (1) Removes rust from iron and steel surfaces, 2) treats metal surfaces, including galvanized and aluminum, to allow better paint adhesion, and (3) etches concrete to allow paint or stains to penetrate and adhere. WM Barr GKPA30220 Phosphoric Prep & Etch, Gallon Features: Removes rust from metal surfaces and prevents flash rusting Etches masonry and concrete surfaces Helps insure good paint adhesion 1 gallon