Electroplating – A Brush Plating Overview
Many of us have cheap jewellery which has a fine coating of precious metal over a cheaper base metal, such as copper or brass. This fine outer coating is the result of electroplating. Basically, electroplating is an electrochemical reaction used to deposit a thin metal coating onto an electrically conductive object. As well as its use for producing cheap jewellery, electroplating has been used in the automotive industry since the early 1920s by way of chrome plating and is still in extensive use today.
The process of electroplating is also referred to as electro-deposition and is a fairly simple process. Firstly, a negative charge is placed on the object that will be electroplated, the object to be plated being referred to as the cathode. The positive charge is applied to a wand with swabbing on the end, referred to as the anode. The wand is then immersed in an electrolyte solution containing the dissolved metal that will be used to plate the object. Once the saturated swabbing comes into contact with the object to be plated it completes the circuit, the charged particles of dissolved metal bond to the cathode and you have your newly electroplated object.
With tank electroplating, controlling the thickness of the electroplated object is generally achieved by adjusting the time it spends in the tank. The longer it remains inside the tank, the thicker the electroplating layer becomes. To be able to control the thickness of the coating when brush plating a different technique is applied based on the volume of solution and surface area to be brush plated.
Before electroplating an object, it must be cleaned thoroughly. All scratches and other imperfections must be polished out of the object in order to obtain the desired result, often a smooth mirror finish surface. Recessed areas will be more difficult to polish and may plate less than other external surfaces, due to wand access, so a scratch may become more prominent, rather than being smoothed over by the plating process.
Brush plating is extremely Flexible and versatile. Due to the equipment needed, you can use this as a portable process in the workshop or out in the field. It is used on site to perform operations such as selectively plating nickel onto areas of the international space station, touching up defective cadmium on aircraft landing gear and repairing scores and pits in the valve stems at nuclear power plants.
