**2.1. Current density**

Electrodeposition process consists of two steps that are nucleation, growth mechanisms and thickening of the primary layer. The nucleation is enhanced by high current density unlike the growth process [1]. Thus, smaller grain sizes are observed at higher current densities due to the increase in the nucleation rate [2]. On the other hand, high current density increases pH in the vicinity of the electrode during the reduction process that creates a competition between metal deposition and hydrogen gas [6] [3]. Hydrogen evolution contributes to the internal stress in the deposit [4][5]. Therefore, it is important to figure out the current density values at which hydrogen evolution does not occur together with metal deposition [4].

The current density also affects the particle content in the deposit. The particle (WC) content of the coating increases linearly with an increase in the current density from 0.1 to 0.5 A/dm2 regardless of the particle diameters [7]. On the other hand, Kuo [6] claims that the particle (MoS2) content in the deposit decreases when the current density increases from 4 to 8 A/ dm2. According to the results of Hu and Bai [41], increasing current density generally increased the particle content but the effect of current density depends on pH. Figure 1 shows that when the current density (B) is increased, the particle content is increasedwhen pH (C) is 1 and decreased when pH is 5 [41].

coatings are composed of an electrodeposited metal matrix and dispersed solid particles. The metal powders, metal alloy powders and metal oxide powders of Al, Co, Cu, In, Mg, Ni, Si, Sn, V, Zn and nitrides of Al, B, Si and C (graphite or diamond) and carbides of B, Bi, Si, W and MoS2 and organic materials such as polytetrafluoroethylene (PTFE) and polymer spheres are

The main application areas of the composite deposition are electronic, biomedical, telecom‐ munication, automotive, space and consumer applications where high strength, equiaxed

The electroplating parameters must be controlled during electrodeposition since they have significant effect on the coating properties, deposition efficiency and hydrogen evolution. Besides the current density, pH of the bath, bath temperature that places among the main electroplating parameters [36], there are more parameters including the type, the size, the concentration of the particles [37] and the addition of surfactants and their types [20]. The main properties of the coating can be listed as the corrosion resistance in TiO2 – nickel coating [38], tribological properties in MoS2 – nickel coating [4], mechanical properties in TiO2 – nickel coating [38], internal stress in MoS2 – nickel coating [9], texture in chromium – carbon deposit [39], particle content of the deposit [24] are severely affected by the electroplating parameters. The aim of this chapter is to emphasize on the electroplating parameters, their effects and interaction effect on the coating properties. Particle incorporation in the deposit is an important property that must be analysed since composite electroplating aroused in order to improve the matrix properties with particle addition. Another important property is the internal stress

Electrodeposition process consists of two steps that are nucleation, growth mechanisms and thickening of the primary layer. The nucleation is enhanced by high current density unlike the growth process [1]. Thus, smaller grain sizes are observed at higher current densities due to the increase in the nucleation rate [2]. On the other hand, high current density increases pH in the vicinity of the electrode during the reduction process that creates a competition between metal deposition and hydrogen gas [6] [3]. Hydrogen evolution contributes to the internal stress in the deposit [4][5]. Therefore, it is important to figure out the current density values

The current density also affects the particle content in the deposit. The particle (WC) content of the coating increases linearly with an increase in the current density from 0.1 to 0.5 A/dm2 regardless of the particle diameters [7]. On the other hand, Kuo [6] claims that the particle (MoS2) content in the deposit decreases when the current density increases from 4 to 8 A/ dm2. According to the results of Hu and Bai [41], increasing current density generally increased the particle content but the effect of current density depends on pH. Figure 1 shows that when

at which hydrogen evolution does not occur together with metal deposition [4].

used as the particles [40].

28 Electrodeposition of Composite Materials

micro-components are required.

**2. Electroplating parameters**

**2.1. Current density**

that must kept at minimum levels not to disrupt the deposit.

**Figure 1.** The effects and interaction effects of parameters on the atomic percent of phosphorus in the deposit. A: main effect of temperature, B: main effect of current density, BxC: current density – pH interaction effect, AxB: temperature – current density interaction effect [41]

**Figure 2.** Stress behaviour for sulfamate nickel electrolytes with three different chemistries [42]

Another effect of increasing current density from 0.15 to 5 A/dm2 is increasing the internal stress [8] since the stress stems from the residual stresses. However significant effect cannot be detected when the current density increased from 1.2 to 4.8 A/dm2 [9] because the effect of current density on the internal stress depends on the electroplating solution composition. Figure 2 shows the effect of changing only one component amount of the solution on the current density dependence of the internal stress [42]. Moreover the effect of the current density depends on pH.
