Effects of Electroplating Characteristics on the Coating Properties

Electroplating parameters that can be listed as bath temperature, pH of the bath, current density, surfactant addition or type, coating thickness must be controlled during the deposition process since they determine the properties of the coating. However, it is difficult to manage the effects of this high number of parameters including their interaction effects. At this point, fractional factorial design that is a statistical method steps in that have the advantage of evaluating the influences and the complex variable interactions of parameters with a plausible number of experiments. In the design low and high values must be attributed to the parameters before the experiments and these values are selected according to the solution used. There are suitable plating conditions (written in handbooks) for each bath without particle addition and low – high values can be chosen between these ranges or just below or above them. For instance, the temperature range is 40-60°C, current density range is 2-7 A/dm2 and pH range is 3.5-4.0 for nickel electroplating [36]. Besides the coating property, the electroplating parameters influence the hydrogen evolution reaction that is a side reaction that takes place at the cathode and may lead to morphological problems on the coated surface. The aim of this chapter is to provide information about how the parameters affect the amount of particles in the deposit. Because the reason of adding the particles to the bath is to improve the matrix properties by the particles emerged. So the more particles present and disperse in the coating, the more they will contribute to the coating property. Another important effect is the internal stress that led to departure of the deposit.