Nanocomposite Coatings Obtained by Electro-Co-Deposition of Inert Particles with Cobalt–a Review

The paper focuses on review investigations of electrodeposition processes of metallic coatings containing dispersed nanosized particles. The nanosized particles, suspended in the electrolyte by agitation and/or use of surfactants, can be electroco-deposited with the metal. The inclusion of nanosized particles can give (i) increased microhardness and corrosion resistance, (ii) modified growth to form a nanocrystalline metal deposit and (iii) a shift in the reduction potential of a metal ion. Many operating parameters influence the quantity of incorporated particles, including current density, bath agitation (or movement of work piece) and electrolyte composition. High incorporation rates of the dispersed particles have been achieved using (i) a high nanoparticle concentration in the electrolyte solution, (ii) smaller sized nanoparticles; (iii) a low concentration of electroactive species, (iv) ultrasonication during deposition and (v) pulsed current techniques. Compositional gradient coatings are possible having a controlled distribution of particles in the metal deposit and the theoretical models used to describe the phenomenon of particle co-deposition within a metal deposit are critically considered