Method for oxalating the galvanized surface of sheet metal
AssigneeUsinor
InventorsJacques Petitjean, Genevieve Klam
Life of this patent
Estimating the term…
Abstract
A method for forming a zinc oxalate coating on the surface of a strip or sheet of metal covered with a zinc or zinc alloy coating other than zinc/iron coatings, with the aid of an aqueous solution consisting of oxalic acid having a concentration of between 5.10−3 and 0.1 mole/l, and at least one compound and/or ion of an oxidant zinc metal having a concentration of between 10−6 and 10−2 mole/l, and possibly a wetting agent. The inventive method enables sheet metal to be treated at very high speeds without using large amounts of oxidant. It facilitates management of treatment baths. The invention can be used in the lubrication of sheet metal, especially for die stamping.
Claims10
Method for forming a zinc oxalate layer on the surface of a metal strip or sheet coated with a layer of zinc or zinc alloy, with the exception of zinc-iron alloys, by means of an aqueous oxalation solution containing oxalic acid, characterized in that said solution is an aqueous solution of oxalic acid in a concentration between 5×10−3 and 0.1 mole/L incorporating at least one compound and/or one ion of a zinc oxidizing metal in a concentration of between 10−6 and 10−2 mole/L, and possibly a wetting agent.
Method according to any of the preceding claims, characterized in that at least one ion is chosen from the group comprised of Ni2+, Co2+, Cu2+, Fe2+, Fe3+, Mo3+, Sn2+, Sn4+.
Method according any of the preceding claims, characterized in that said solution is applied to said galvanized surface without electrical polarization of said sheet.
Method according any of the preceding claims, characterized in that the GSM of said zinc oxalate layer is between 0.05 and 3 g/m2.
Dependencies are inferred from the claim text.