Newly Developed Nickel-Boron Composite Surface Coatings with Pd Particles: Structural, Mechanical and Corrosion Properties

Ni-B and Ni-B-Pd composite coatings have been electrodeposited from an aqueous electrolyte using direct current. The Ni-B composite coating has been observed to be dense, smooth, and shows a globular, cluster of grains type morphology. On the other hand, the Ni-B-Pd composite coating is observed to be porous, highly rough and shows stacked crystal type morphology. The addition of palladium has significantly improved the crystallite size of the coating. From DSC analysis, it is observed that the Ni-B-Pd composite coating is thermodynamically more stable than the Ni-B composite coating. In spite of larger grain size and higher roughness the Ni-B-Pd coating is observed to exhibit higher hardness (≈40% higher) and elastic modulus (≈70% higher) than that of the Ni-B composite coating. Also, it has been observed to possess better protective property (almost three times) than that of the Ni-B composite coating.