Electroplating is the process of applying a metallic coating to a metal or any conducting surface through an electrochemical process. It is an electro-deposition process aimed at producing an uniform, dense and adherent coating usually of alloys or metals, through the action of an electric current (Lou & Huang, 2006). The coating developed is usually for aesthetic or protective purposes or the enhancement of the surface. Aesthetics involves beauty. Electroplating may be used to coat a metal with shiny or precious and semi-precious metals such as silver or gold. The surface may be made up of conductors like metal or even non-conductors like plastics. Products developed through electroplating is widely used in many industries such as ship building, automobile, airspace, electronics, jewellery, toy industries, precision equipment such as watches and clocks as well as in defense equipment. The main part of the electroplating process is known as the electrolytic cell. The article being electroplated (the work) is placed as the negative electrode (cathode) of an electrolysis process cell. A direct electric current is passed through the electrolysis circuit. The article is then immersed in an aqueous solution that contains the metal to be used for electroplating in an oxidized form. An aqueous solution is one in which water is used as a solvent. This required metal (sacrificial anode or dissolvable anode), is either in the form of a complex ion or an aquated cation while the anode usually consists of the metal that is being plated. A complex ion is a group a group of cations whose water molecules have been replaced by an electron pair donor. The permanent anodes can only make the electrical circuit complete but cannot act as a source of fresh metal to replenish what has been extracted from the solution through deposition at the cathode. Permanent anodes are those anodes which do not get depleted in the electroplating process.
The anodes are usually made of carbon or platinum. The electrolyte is the electrical conductor through which current is carried by ions (and not free electrons as in metals). The electrolyte makes an electric circuit complete between two electrodes. After an electric current is applied, the positive ions of the electrolyte move towards the cathode while the negatively charged ions flow towards the anode. This migration of ions makes up the electric current on this end of the circuit while the migration of electrons through the anode past the wiring and the electric generator then back to the cathode makes up the external circuit current. The metallic ions of the electrolyte (salt) bear a positive charge and are, therefore, attracted to the cathode. When these ions reach the negatively charged work piece, it emits electrons to reduce the positively charged ions into a metallic form, while the metal atoms are deposited onto the negatively-charged work piece (article). This process is shown in the figure below
Figure 1: Electroplating process
In this case, as shown in figure 1 above, the electrolyte comprises of copper sulphate solution (CuSO4). The cathode the work piece to be plated which is negatively charged, thereby attracting positive (Cu2+) ions. The anode is made of copper metal which has a charge of (2+). Its ions are set free to move across the electrolyte to the cathode (object to be plated).
References
Lou, H. H., & Huang, Y. (2006). Electroplating. Encyclopedia of Chemical Processing, 4(2), 1-10.
