Patent ID: 8349092

Claim:
A process comprising: applying an aqueous, acidic phosphating solution comprising dissolved contents to a metallic surface, said metallic surface comprising at least 5% by weight of at least one of aluminum or an aluminum alloy, wherein the dissolved contents in the phosphating solution comprise: having a combined sodium and potassium content in the range of 0.3 to 1.8 g/L as sodium, the potassium content being converted to sodium on a molar basis; zinc in a concentration range of 0.2 to 4 g/L; phosphate in a concentration range of 4 to 65 g/L, calculated as PO 4 ; free fluoride in a concentration range of 0.03 to 0.5 g/L; total fluoride in the concentration range of 0.1 to 5 g/L; silver in the concentration range of 0.001 to 0.080 g/L; wherein a zinc-containing phosphate film is deposited on the metallic surface and has a coating weight in the range of 0.5 to 10 g/m 2 , whereby free acid in the phosphating solution is maintained in the range of 1.6 to 2.8 points as measured by FA-KCl, wherein the process is conducted without a precipitation tank, whereby precipitation products from an Al—F complex are scarcely deposited on the metallic surface so that there is no significant deterioration of corrosion resistance by the precipitation products, wherein the content based on hydroxylamine is virtually none, and wherein no copper is added.