**3.1. Definition of Co-deposition process**

Co-deposition is a process of incorporating fine particles of metallic, non-metallic compounds, or polymers from an electrolytic or an electroless bath in the electroplated layer to improve material properties such as: hardness, wear-resistance, corrosion-resistance, tribological control, lubrication, tensile, and fracture strength [32].

Co-deposition of particles into metal deposit is governed by physical dispersion of parti‐ cles in the electrolyte and electrophoretic migration of particles [33]. Among different models presented for co-deposition mechanism of solid particles into a metal matrix, Guglielmi's model is the most adopted one. It has also been examined with different co-deposition systems such as: Ni−SiC, Ni−TiO2, Ni- Al2O3, Cu- Al2O3, Cr-C, Zn-Ni particles, Co-SiC, and Ni-MoS2 [33, 34]
