HOT-DIP Zn-ALLOY-PLATED STEEL SHEET Russian patent published in 2018 - IPC C23C28/00 C23C2/06 C23C2/26 C22C18/00 C22C18/04 

FIELD: technological processes.

SUBSTANCE: method comprises immersing a steel sheet in molten metal for coating by immersion in molten zinc alloy to form a hot-dip Zn-alloy-plated layer on a surface of steel sheet and contacting with an aqueous solution containing a vanadium compounds to cool the steel sheet and the hot-dip Zn-alloy-plated layer having an elevated temperature, and to form complex oxide coating film on the surface of the hot-dip Zn-alloy-plated layer. Surface temperature of the hot-dip Zn-alloy-plated layer, when the aqueous solution must contacting with the surface of the hot-dip Zn-alloy-plated layer, is equal to or greater than 100 °C, and is equal to or less than curing temperature of the hot-dip Zn-alloy-plated layer. Complex oxide coating film includes vanadium and the constituent component of the hot-dip Zn-alloy-plated layer and the entire surface of the coating film satisfies the following formula (1):

In formula (1): S[oxide] is the exhibited area by a peak having a center at approximately 1,022 eV ascribable to a Zn oxide in an intensity profile in XPS analysis of the surface of the complex oxide coating film; and S[hydroxide] is the area exhibited by a peak having a center at approximately 1,023 eV ascribable to a Zn hydroxide in an intensity profile in XPS analysis of the surface of the complex oxide coating film.

EFFECT: invention relates to the manufacture of a hot-dip Zn-alloy-plated steel sheet with an excellent darkening resistance.

4 cl, 7 dwg, 10 tbl