Solution for reducing the blackening or tarnishing of a metal sheet and metal sheet
AssigneeArcelormittal Investigacion Y Desarrollo, S.L.
InventorsDaniel Chaleix, Christian Allely, Maxime Monnoyer, Pascale Feltin
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Abstract
The present invention provides an aqueous treatment solution containing sulfate ions SO42− in a concentration greater than or equal to 0.01 mol/l, to treat sheet metal including a steel substrate coated on at least one face with a coating including at least zinc and magnesium to reduce blackening or tarnishing of the sheet metal during storage. The present invention also provides a sheet metal treated with a solution of this type.
Claims30
A method to reduce blackening or tarnishing of a steel sheet during storage comprising the steps of:
- providing an aqueous treatment solution containing sulfate ions SO42− in a concentration greater than or equal to 0.01 mol/l;
- providing a steel sheet comprising a substrate of steel coated on at least one face with a coating comprising at least zinc and a stabilizing amount of magnesium;
- treating the steel sheet with the aqueous treatment solution to form a zinc hydroxysulfate/zinc sulfate-based temporary protection layer on the surface of the treated steel sheet;
- and
- stabilizing the zinc hydroxysulfate/zinc sulfate-based temporary protection layer with the stabilizing amount of magnesium in the coating to prevent the transformation of zinc hydroxysulfate to zinc carbonates in the presence of atmospheric CO2 to reduce blackening or tarnishing of the steel sheet during storage;
- and
- coiling and storing the treated steel sheet, wherein the treated steel sheet is not oiled prior to coiling and storing.
A method to reduce blackening or tarnishing of a steel sheet during storage comprising the steps of:
- providing an aqueous treatment solution containing sulfate ions SO42− in a concentration greater than or equal to 0.01 mol/l;
- providing a steel sheet comprising a substrate of steel coated on at least one face with a coating comprising at least zinc and a stabilizing amount of magnesium;
- treating the steel sheet with the aqueous treatment solution to form a zinc hydroxysulfate/zinc sulfate-based temporary protection layer on the surface of the treated steel sheet;
- and
- stabilizing the zinc hydroxysulfate/zinc sulfate-based temporary protection layer with the stabilizing amount of magnesium in the coating to prevent the transformation of zinc hydroxysulfate to zinc carbonates in the presence of atmospheric CO2 to reduce blackening or tarnishing of the steel sheet during storage;
- and
- storing steel sheet after treating the steel sheet with the aqueous treatment solution for at least 12 weeks,
- the treated steel sheet not being oiled prior to the step of storing.
Dependencies are inferred from the claim text.