Electrodeposition behavior of Mg with Zn from acidic sulfate solutions

Electrodeposition of Mg with Zn in acidic sulfate solutions with polyethylene glycol and octadecyl dimethyl benzyl ammonium chloride as additives was investigated by scanning electron microscopy, X-ray diffraction, and potentiodynamic polarization techniques. The results show that these two compounds act in a synergetic way to suppress Zn deposition markedly and facilitate Mg reduction. Zn–0.46%Mg coatings are produced under high cathodic current densities, which have lower corrosion potentials than Zn coatings and hydrogen evolution in neutral chloride solutions. Magnesium hydroxide may cause current oscillations at high cathodic polarizations in plating solutions without zinc salts due to its formation and peel-off. An “induced co-deposition” mechanism is proposed for Zn–Mg alloy electrodeposition.