A study of zinc–nickel alloy electrodeposition from an alkaline electrolyte

• I.A. Adudin, N.S. Grigoryan, A.N. Serov, T.A. Vagramyan, K.A. Orlova, M.A. Shelukhin and V.Kh. Aleshina

Federal State-Funded Educational Institution of Higher Education “D. Mendeleev University of Chemical Technology of Russia”, Miusskaya sq. 9, 125047 Moscow, Russian Federation

Abstract: An alkaline electrolyte with an amine-containing organic ligand (onwards L) for the electrodeposition of zinc–nickel alloy onto the surface of steel products with the aim of replacing the toxic cadmium-plating electrolyte has been developed. The electrolyte contains (mol/L): Zn²⁺ 0.07–0.14; Ni²⁺ 0.03–0.06; L (aliphatic amine-containing ligand) 0.1–0.2, pH 13–14, t = 22°С. The alloy composition remains constant at various mole ratios of Ni/L in the electrolyte in a wide range of current densities. A coating containing 12–14% Ni can be obtained from the electrolyte with a molar ratios Ni/L 0.6 and Ni/Zn 0.4. Such ratio produces a coating with the highest corrosion resistance while preserving the electrochemical character of protection of the steel base. The nickel content in the coating increases with an increase in the electrolyte temperature. In heated solutions with the total metal content of 0.2 mol/L, the increase of Ni/L ratio in the electrolyte significantly increases the nickel content in the coating. In cold solutions such an increase is insignificant. At the total metal concentration of 0.1 mol/L the increase of the molar ratio Ni/L does not lead to such an apparent increase of nickel content in the coating. It has been determined that the developed zinc–nickel coatings in terms of protective ability and corrosion resistance are significantly superior to zinc coatings, and are comparable to cadmium coatings.

Keywords: electrodeposition, zinc–nickel alloy, Zn–Ni, alkaline electrolyte, corrosion protection, electroplating technology, surface treatment

Int. J. Corros. Scale Inhib., 2021, 10, no. 2, 580-591 PDF (551 K)
doi: 10.17675/2305-6894-2021-10-2-6

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