RSM optimization of pulse electrodeposition of Zn-Ni-Al2O3 nanocomposites under ultrasound irradiation

In the present paper, Zn-Ni nano-Al2O3 containing coatings were pulse-plated on mild steel substrates in a chloride bath under ultrasound irradiation. A Box Behnken design of experiments was used for the statistical modeling and analysis of the alumina volume percent in the coating and coating microhardness as the response variables influenced by the effect of three process variables: peak current density (A), pulse frequency (B), and ultrasonic power (C). Quadratic models were developed and found to be mathematically appropriate to describe the significant effects and also to optimize the process. Moreover, scanning electron microscopy, energy dispersive spectroscopy technique, and X-ray diffraction analysis were employed to study the morphology, composition and phase composition of the coatings. The optimum level of parameters were found to be A = 16.6–17.1 A/dm2, B = 103–120 Hz, and C = 34–60 W giving an alumina content of 17.7–18.0 vol% and a microhardness of 753 to 774 HV. •Electroplated Zn-Ni-Al2O3 coatings produced with exceptional hardness properties.•An image processing method is used to estimate the vol% of co-deposited alumina.•Using a Box-Behnken methodology of optimization, Al2O3 co-deposition is maximized.•Surface morphology is highly affected by pulse plating and ultrasonic parameters.