METHOD OF PRODUCING CORROSION-RESISTANT ELECTROCHEMICAL ZINC-NICKEL-COBALT COATING Russian patent published in 2020 - IPC C25D3/56 

FIELD: technological processes.

SUBSTANCE: invention relates to electroplating, in particular to processes of electrochemical deposition of coating Zn-Ni-Co, and can be used in production of structural corrosion-resistant materials for operation in aggressive media. Method involves electrodeposition of zinc-nickel-cobalt coating on steel surface subjected to preliminary mechanical treatment, degreasing, etching, removal of oxide films with subsequent washing in water, wherein electrodeposition is carried out using reverse mode from 125 to 155 cycles of electrolysis at cathode current density i_k=0.5–2.0 A/dm², anode current density i_a=4.0–5.0 A/dm², at duration of cathode polarization of one cycle τ_k=15–20 s and duration of anode polarization of one cycle τ_a=1.0 s, at temperature of electrolyte with graphite anode from 20 °C to 25 °C, pH from 4.5 to 5.5, wherein electrolyte additionally contains salt of sulfuric acid Na₂SO₄, as ZnSO₄ contains ZnSO₄⋅7H₂O, as NiSO₄ – NiSO₄⋅7H₂O, as CoSO₄ – CoSO₄⋅7H₂O with following ratio of components, g/l: ZnSO₄⋅7H₂O 60.0–72.0; NiSO₄⋅7H₂O 34.0–39.0; CoSO₄⋅7H₂O 19.7–33.7; Na₂SO₄ 60.0–72.0; glycine 52.5–70.0; water – rest.

EFFECT: reduction of corrosion current, which leads to increase of corrosion resistance and uniformity of microstructure of applied coating, intensification of process of electrochemical deposition and reduction of time of process, as well as improvement of environmental safety and reduction of economic costs of production.

1 cl, 16 ex