Anomalous Coating of Iron Microparticles by Ni–Co Layers in the 3D Stirred Heterogeneous System: Impedance Study

Abstract

A high level controlled electrochemical metal plating of the homogeneous, uniform, and adhesive Ni–Co nano-/microlayer on an Fe microparticle powder substrate in the stirred heterogeneous system (SHS) is reported. The influence of the volume fraction of suspended powder particles on the partial current efficiency of the electrolytic coating process is evaluated using electrochemical impedance spectroscopy. The role of both the solid Fe powder microparticles and the electrochemical deposition of binary coating on the particle surface of the charge-transfer mechanism through SHS is discussed. The equivalent circuit on the porous electrode model is proposed and, adopting this approach, some calculations and simulations of the experimental data are done. The optimal volume fraction of solid particles in the charge transfer of our SHS is suggested. The formation of permanent aggregates of powder microparticles during the electrolysis is proved. Scanning electron microscopy, optical microscopy, atomic absorption spectroscopy, and energy dispersive X-ray spectroscopy are used to characterize the coating on the microparticle surface.