Characterisation of coelectrodeposited Ni–Al composite coating

Abstract

Ni–Al composite coating was prepared by coelectrodeposition technique in Watt’s bath containing dispersed Al particles to be codeposited. Pure Ni coating was also prepared as a comparison. Morphology and composition studies showed that Al particles were uniformly distributed in the Ni matrix. Microhardness measurements and microstructure studies revealed that the incorporation of Al particles lowers the microhardness of Ni coating due to the high ductility of Al and weak bonds between Al and Ni. The results of potentiodynamic polarisation tests demonstrated that the corrosion resistance of Ni–Al composite coating is lower than that of pure Ni. The microstructure and corrosion path studies revealed that the lower corrosion resistance of Ni–Al composite coating is resulted from weak bonds between Al particles and Ni matrix and formation of active–passive cells on the surface of the coating.

Keywords:

• Ni–Al composite coating
• Coelectrodeposition
• Microhardness
• Corrosion resistance