Abstract: A method for treating magnesium die castings sufficiently cleans the die castings and improves their paint adhesion and corrosion resistance by utilizing hydroxy acetic acid, among other constituents. The method includes cleaning the castings with an alkaline cleaning solution, rinsing with water, pickling the castings with an aqueous hydroxy acetic acid solution, rinsing with water again, and then contacting the castings with a chrome-free pretreatment. The alkaline cleaning and pickling steps appear to remove substantially all die casting impurities in order to adequately prepare the metal for application of the pretreatment. The chrome-free pretreatment may be an organofunctional silane solution or an aqueous polymeric system having hydroxyl and carboxylic functional groups along with a compound of a group IV-B element. The pretreatment is then painted or contacted with another decorative coating, with no rinsing step occurring between the pretreatment and painting steps.

Abstract: A method and composition for forming a zinc phosphate coating on a metal surface utilizes an aqueous solution of zinc, phosphate, nitrate, nickel, a compound containing a group IV-B element, and a fluosurfactant. The method involves contacting the metal surface with such a bath under process conditions such that a coating is formed on the metal surface. Preferably, the compound containing a group IV-B element is a fluoacid of titanium, zirconium, or hafnium. More preferably, the fluoacid is fluotitanic acid. The fluosurfactant may be any compatible fluosurfactant but preferably is an amine perfluoroalkyl sulfonate or a non-ionic, fluorinated alkyl polyoxethylene ethanol or a combination of both. The coating serves to improve the ability of the metal to retain a lubricant on its surface (for cold working of the metal), to improve corrosion resistance, and to improve paint adhesion.