Method for the preparation of a coated metal sheet, comprising the application of an aqueous solution containing an amino acid, and associated use in order to improve corrosion resistance

A method for preparing a metal sheet comprising at least the steps of:

• providing a steel substrate, at least one face of which is coated with a metal coating comprising at least 40% by weight of zinc,
• applying on the outer surface of the metal coating an aqueous solution comprising an amino acid selected from among alanine, arginine, aspartic acid, cysteine, glutamine, lysine, methionine, proline, serine, threonine, and a mixture thereof, each amino acid being in a neutral or salt form,
• the aqueous solution being free of any compound comprising a metal from the group IIIB or from the group IVB, and
• the mass percentage as a dry extract of the amino acid in neutral or salt form or of the mixture of amino acids in the neutral or salt forms in the aqueous solution being greater than or equal to 75%.

A method for improving the resistance to corrosion of an outer surface of a metal coating coating at least one face of a steel substrate, comprising at least the steps of:

• providing a steel substrate having two faces, at least one of which is coated with a metal coating comprising at least 40% by weight of zinc,
• application on the outer surface of the metal coating of an aqueous solution comprising an amino acid selected from among alanine, arginine, aspartic acid, cysteine, glutamine, lysine, methionine, proline, serine, threonine, and a mixture thereof, each amino acid being in the neutral or salt form,
• the aqueous solution being free of any compound comprising a metal from the group BIB or from the group IVB, and
• the mass percentage in dry extract of the amino acid in the neutral or salt form or of the mixture of amino acids in the neutral or salt forms in the aqueous solution being greater than or equal to 75%.

A method for:

• improving the compatibility, with an adhesive, of at least one portion of an outer surface of a metal coating coating at least one face of a steel substrate,
• improving the resistance to corrosion of the outer surface of the metal coating coating at least one face of the steel substrate, and
• improving the tribological properties of the outer surface of the metal coating coating at least one face of the steel substrate,
• said method comprising at least the steps of:
• providing a steel substrate having two faces, at least one of which is coated with a metal coating comprising at least 40% by weight of zinc,
• applying on the outer surface of the metal coating an aqueous solution comprising an amino acid selected from among proline, threonine and a mixture thereof, the proline and the threonine being independently in a neutral or salt form, the aqueous solution being free of any compound comprising a metal from the group TIM or from the group IVB.