Magnetically Induced Codeposition of Ni-Cd Alloy Coatings for Better Corrosion Protection

The effects of applied magnetic field, B (both parallel and perpendicular) during process of electrodeposition of Ni-Cd alloy coating on mild steel from a newly proposed electrolytic bath have been studied by using X-ray diffraction (XRD), energy-dispersive X-ray (EDX), and scanning electron microscopy (SEM) analysis. Both parallel and perpendicular B reduced the corrosion rates (CRs); however, the effect is more pronounced in case of perpendicular B. Progressive decrease of CR with increase in the intensity of B showed that corrosion protection efficacy bears close relation with changed composition and crystallographic orientation of the coatings. Under optimal condition, Ni-Cd coating deposited at 0.8 T (perpendicular) was found to be 35 times less corrosive than the conventional Ni-Cd coating (B = 0 T) deposited from the same bath for same time. The effect of B on thickness, microhardness, surface morphology, composition, and crystallographic orientation, and hence, the corrosion resistance of the coatings were analyzed in the light of magnetohydrodynamic (MHD) effect.