Corrosion behaviour of electrodeposited nanocrystalline Co and Co/ZrO₂ nanocomposite coatings

Abstract

Nanocrystalline Co and Co/nano-ZrO₂ composite coatings were electrodeposited from cobalt sulphate based solutions. Deposition rate, morphology, microstructure, microhardness and corrosion behaviour of the produced coatings were investigated. The results indicated that optimum electrolyte temperature for the best combination of deposition rate and microhardness was 45°C. Incorporation of nanoparticles was increased from 0 to 4·9 vol.-% by increasing of bath ZrO₂ concentration. Co/4·4 vol.-%ZrO₂ nanocomposite coating had the highest hardness value as compared to the composites containing higher or lower volume fractions of incorporated ZrO₂ particles. The polarisation tests in Hanks’ solution revealed that the corrosion potential shifted to more positive values, corrosion current density decreased and polarisation resistance increased by the incorporation of ceramic particles. Impedance tests also confirmed the polarisation results and improvement of pure cobalt corrosion resistance by codeposition of ZrO₂ nanoparticles.

Keywords:

• Electrodeposition
• Cobalt
• Co/ZrO₂ nanocomposite
• Corrosion behaviour