Effect of Current Density on Magnetic and Hardness Properties of Ni-Cu Alloy Coated on Al via Electrodeposition

Nickel (Ni)-rich single-phase nickel-copper (Ni-Cu) alloy coatings were produced on aluminum (Al) substrates by electrodeposition in stabilized citrate baths. Electrodeposition experiments were performed at four different current densities. Increasing the current density resulted in the metal deposition rate increasing faster than the hydrogen evolution rate; thus, the cathodic current efficiency increased. The crystal systems of the Ni-Cu alloys were face center cubic (fcc), with the (111) plane as the preferred crystal plane. Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) measurements showed that the Ni content in the coating increased with increasing current density. The Ni-Cu 40 sample had the most Ni content and showed a homogeneous and compact morphology. It was found that the higher the concentration of Ni in the solution, the smaller the grain size. Measurements recorded with a vibrating sample magnetometer (VSM) showed that the Ni-Cu 40 sample provided magnetic saturation, with the highest value being 0.108 emu/g. The microhardness method produced 404 HV on the Ni-Cu 40 sample. In conclusion, higher current densities were associated with a higher Ni composition and increased thickness, which were responsible for the increases in the magnetic properties and hardness.