Electroplating is a process that is used to cover a metal object with a layer of some other substance by using an electrical current to bond the two. In brush plating, a brush saturated with the plating material is used to paint the material onto the object to be plated. Plating can be done to increase the strength of a metal part, to resize a part, or for aesthetic reasons. Brush plating is more precise than other methods of electroplating.
A piece of stainless steel that is covered with a cloth is used as the brush. The uncovered end of the steel is attached to the positive node of a power source with a fairly small electrical current, and the other node of the power source is attached to the item to be plated. Like an artist painting a canvas, the operator dips the cloth end of the brush into a vat of the plating solution, soaking the brush. He or she then paints the material onto the item to be plated. The current running through both the brush and item bonds the plating to the item.
Often, the goal of plating a metal part is to protect the metal from damage or corrosion. For example, parts of a pump that will be exposed to water may be plated to keep them from rusting. In some cases, plating is done for purely aesthetic reasons, such as when gold is plated onto a less expensive metal to make jewelry. Plating can also be used to resize parts that have worn down or were manufactured in the wrong size. Brush plating is especially good for resizing because the person doing the plating can apply different amounts of plating material to different areas of the same part.
Aside from the precision possible with brush plating, several other characteristics make it preferable to tank plating, which is a method of plating by immersing the metal in a tank of plating material and then passing an electrical current through it. Brush plating has a bond strength of about 14,000 pounds per square inch (about 984 kilograms per square centimeter),which is more than double the bond strength of tank plating. Brush plating can also be used when tank plating would be impractical, for example when a part cannot be removed from the machine or when the part is too large to fit in a standard tank.