PROCESS OF PHOSPHATING METAL SURFACES USING NICKEL FREE PHOSPHATING SOLUTIONS

摘要

In a process of phosphating metal surfaces phosphating solutions are employed which are substantially free of nickel and contain 0.3 to 1.7 g/l Zn 0.2 to 4.0 g/l Mn 0.001 to 0.030, preferably 0.003 to 0.020 g/l Cu to 30 g/l phosphate (calculated as P2O5) in which by oxygen and/or other equivalent oxidizers the concentration of Fe(II) is kept below 0.1 g/l and which are adjusted to a pH value from 3.0 to 3,8. The weight ratio of Cu to P2O5 is preferably adjusted to 1 : (170 to 30,000) and Cu and P2O5 are preferably replenished in a weight ratio of 1 : (5 to 2000). The phosphating solutions should contain 0.3 to 1.0 g/l Zn if they are applied by spraying and should contain 0.9 to 1.7 g/l Zn if they are applied by spraying/ dipping operations or by a dipping operation. The process serves particularly for the pre-treatment of metal surfaces for a succeeding painting; particularly by electro-dipcoating, aid for the phosphating of steel, galvanized steel, zinc alloy-plated steel, aluminum and its alloys.