Magnetic field-induced codeposition of (Ni-Co) alloy coatings for better corrosion protection

This paper explores the benefit of induced magnetic field (B) in the co-deposition of (Ni-Co) alloy coatings for better corrosion protection. The phenomenon of magnetohydrodynamic (MHD) convection has been used as the tool to deposit (Ni-Co) alloy coatings of high corrosion protection from an electrolytic bath having low [Co+2] ions. Experimental studies demonstrated that under optimal conditions of magnetic field intensity (B), magneto-electrodeposited (MED) coatings, developed under parallel (||) and perpendicular (perpendicular to) magnetic field, are respectively about 3 times and 11 times more corrosion resistant than conventionally electrodeposited (ED) alloy coatings, developed from the same bath. The properties of MED (Ni-Co) alloy coatings were found to be changed with the direction of the applied B. The reasons responsible for improved corrosion performance of MED (Ni-Co) alloy were explained through FESEM, EDX and XRD analyses. Attempt has been made to understand changed properties of MED alloy coatings in the light of magnetic field controlled diffusion of Co+2 ions and increase in its limiting current density (iL). The improved corrosion resistance of MED (Ni-Co) alloy coatings, compared to ED (Ni-Co) alloy coatings were attributed to its increased Co content, affected due to forced convection of magnetoelectrolysis, and experimental results are discussed.