BigPatents India

An aluminum alloy substrate is pretreated with an aqueous solution containing an organophosphorus compound, preferably a vinylphosphonic acid-acrylic acid copolymer, before coating the substrate with a polymer. Passing the substrate through the solution contaminates it with aluminum and other elements. The pretreatment solution is rejuvenated by removing aluminum with a cation exchange resin that preferably contains a styrene-divinyl benzene copolymer functionalized with sulfonate groups. Rinsing the substrate contaminates the rinse water with the copolymer. The rinse water is concentrated by reverse osmosis or membrane ultrafiltration and retured to the pretreatment solution. Drawing Sheets. 01 Total Pages: 12 (FIG.01)