An investigation on the effect of surface morphology and crystalline texture on corrosion behavior, structural and magnetic properties of electrodeposited nanocrystalline nickel films

Abstract

In this work, nanocrystalline nickel films with different surface morphologies were electrodeposited from Watts bath using direct (DC), pulsed (PC), and pulsed reverse (PRC) current techniques. The effect of electrodeposition conditions on the evolution of microstructure, cathodic efficiency, crystallographic micro-texture, micro-hardness, magnetic and corrosion properties of nickel films were investigated. Ni films electrodeposited by PC method revealed the highest cathodic efficiency due to minimum amount of hydrogen evolution. All films electrodeposited by PC and PRC methods making the films nanocrystalline (NC) exhibited greater hardness values and smaller crystallite size compared to those deposited by DC method. A preferential crystallographic orientation or texture was found in Ni films depending upon the electrodeposition pulse shape, as the microstructure is polycrystalline in the DC electrodeposited films, while exhibits 〈111〉 and 〈100〉 crystallographic growth directions for PC and PRC methods, respectively. Magnetic properties of the nanocrystalline Ni films indicate the existence of strong magnetocrystalline anisotropy depending on the microstructure of the films. Corrosion evaluation results showed that the PC electrodeposited NC-Ni films are more corrosion resistive in 2mol/l NaOH solution, compared to those electrodeposited by PRC and DC methods. In contrast, in 0.5mol/l H2SO4 solution, corrosion resistance of the films is in descending order from PC to PRC and DC.