Surface-treated steel sheet and method of producing same
AssigneeJfe Steel Corporation
InventorsTakashi UENO, Yusuke NAKAGAWA
Life of this patent
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Abstract
Provided is a surface-treated steel sheet that can be produced without using hexavalent chromium and is excellent in adhesion to BPA-free paint and BPA-free painting corrosion resistance. A surface-treated steel sheet comprises: a steel sheet; a metallic Cr layer disposed on a surface of the steel sheet on at least one side; and a Cr oxide layer disposed on the metallic Cr layer, wherein a contact angle of ethylene glycol is 50° or less, and a total atomic ratio of K, Na, Mg, and Ca adsorbed on a surface of the surface-treated steel sheet on the at least one side to Cr is 5.0% or less.
Claims16
A surface-treated steel sheet comprising:
- a steel sheet;
- a metallic Cr layer disposed on at least one surface of the steel sheet;
- and
- a Cr oxide layer disposed on the metallic Cr layer, the surface-treated steel sheet having:
- a contact angle of ethylene glycol of 50° or less, and
- a total atomic ratio of K, Na, Mg, and Ca adsorbed on a surface to Cr of 5.0% or less.
A method of producing a surface-treated steel sheet that includes:
- a steel sheet;
- a metallic Cr layer disposed on at least one surface of the steel sheet;
- and a Cr oxide layer disposed on the metallic Cr layer, the method comprising:
- an electrolyte preparation process of preparing an electrolyte containing trivalent chromium ions;
- a cathodic electrolysis treatment process of subjecting the steel sheet to cathodic electrolysis treatment in the electrolyte;
- an immersing process of immersing the steel sheet after the cathodic electrolysis treatment in the electrolyte for 1.0 second or more and 5.0 seconds or less electrolessly;
- and
- a water washing process of at least one water wash of the steel sheet after the cathodic electrolysis treatment,
- wherein, in the electrolyte preparation process, the electrolyte is prepared by:
- mixing a trivalent chromium ion source, a carboxylic acid compound, and water;
- and
- adjusting the pH to 4.0 to 7.0 and adjusting the temperature to 40° C. to 70° C., and
- in the water washing process,
- water having an electrical conductivity of 100 μS/m or less is used in at least the last water wash.
Dependencies are inferred from the claim text.