Pulse electrodeposition and characterization of Zn–Mn coatings deposited from additive-free chloride electrolytes

Zn–Mn coatings were deposited by means of pulse plating on steel substrates from additive-free chloride electrolytes. Theoretical aspects of the pulse plating of Zn–Mn alloys were considered for defining the optimal range of electrical and time parameters prior to deposition. The influence of the average and peak current densities as well as the time parameters—namely on- and off-time—on the deposit properties was investigated. In order to determine optimal deposition parameters, the composition, morphology, texture and crystallinity were characterized by means of scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and X-ray diffraction (XRD). Deposits obtained by applying a continuous current exhibited a rough surface with the presence of pores and cracks, a Mn content of 13 wt% and faradaic efficiencies of 65%. By comparison, homogeneous, compact and pore-free deposits containing up to 15 wt% Mn and with a monophasic ε 2 -ZnMn crystallography were obtained with efficiencies up to 90% using pulse plating. Graphical abstract