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What is Electroless Plating?

Dale Marshall
Dale Marshall

Electroless plating is a method of bonding a thin, uniform coat of metal onto a workpiece without having to use electricity to form the plate. Many differences set electroless apart from traditional plating methods, but two stand out. First, electroless plating is the first method that achieves results at least as good as those achieved by electroplating methods, which require an electric current to form the plate. Second, since no current is required, the workpiece itself can be of either conductive or non-conductive materials. Thus, while electroplating is restricted to metal workpieces, workpieces of any type, including rubber, fiberglass and plastic, can be plated using the electroless process.

Both traditional electroplating and electroless plating involve submerging the workpiece in a chemical bath. In electroplating, the plating metal — typically chrome, nickel or copper — is either present in the bath as dissolved salts, or as the anode itself in an electric circuit. The workpiece is attached to the anode and submerged in the bath, which is heated and agitated. When the current is activated, the metal ions migrate to the workpiece, also called the cathode, and bond with it. A notable drawback to electroplating is that the metal doesn’t plate in a uniformly thick coat, but tends to concentrate in certain places and avoid others, based both on the workpiece’s geometry and the placement of the anodes in the bath.

Man with a drill
Man with a drill

The electroless process has several similarities to electroplating. The metal is suspended in the chemical bath, and when a reducing agent is added, the chemical reaction begins, imparting a negative charge to the workpiece and attracting the positively-charged metal ions. The metal bonds to the workpiece, regardless of geometry, resulting in a plate of uniform thickness. Both are used to produce a bright, hard shiny surface on the workpiece.

Electroless plating offers several advantages over electroplating for a number of applications, both in the process and the final result. The electroless chemical bath doesn’t require agitation or electricity, relying instead on a chemical reaction for the deposition of the metal on the workpiece. Electroless plating enhances the level of corrosion protection because the end product is usually less porous than that of electroplating, especially in the case of irregularly shaped workpieces where electroplating might not adequately plate depressions or bumps in the surface. One of the major advantages of electroless is that it can be performed on non-conductive materials such as plastic or rubber, which allows manufacturers to construct items, such as automotive trim, plumbing brightwork, and toys, of less costly materials and then plate them.

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