Electrodeposition process optimization by response surface methodologies to obtain high-corrosion resistant Zn-Ni coatings

In the present work, (Zn-Ni) coatings were pulsed-plated over a mild-steel (MS) substrate from an acidic chloride electrolyte. The coating's morphology, topography, chemical composition, and phase composition were evaluated by scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive spectroscopy (EDS), x-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) techniques. Electrochemical methods such as electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests were conducted to assess the coating's corrosion behavior in brine solution. With the help of a Box-Behnken design, the coating's electrochemical performance was assessed under the effect of three electroplating variables: bath temperature (A), plating current density (B), and stirring rate (C). The statistical model found the optimum electroplating variables to be [A = 45 degrees C], [B = 100 mA.cm(-2)], and [C = 0 rpm], yielding corrosion rate and polarization resistance values of 0.61 (+/- 0.10 mm.year(-1)) and 445.52 (+/- 20.23 Omega), respectively.