Electroplating is a versatile finishing process that’s been around since the early 1800s. Simply put, it’s used for applying a metal coating to a substrate using direct electric current. Various plating methods are available today including barrel, vibratory, reel to reel, spotted bed electrode, among others. The process is employed in the manufacture of many commercial, retail and defense products. It’s used to coat anything from jewelry and silverware to mission critical electronic components such as contacts and connectors used in the medical or aerospace markets. Let’s take a closer look at the process, and its compelling history.
How Does Electroplating Work?
The basic electroplating process requires just a few ingredients: two electrodes, one positive and one negative, an electrolyte or solution, and a direct current electrical source. The anode, or positively charged electrode, can be made of the metal being plated or an inert conductive metal. The cathode, or negatively charged electrode, is the object that will be plated. The electrolyte is a solution of a metal salt that will be used for the coating. When electrical current is passed through the solution, the salt ions are separated from the metal ions (positively charged). The positively charged ions, or cations, are attracted to the negatively charged cathode. If the anode is made of the metal to be plated, it too is a source of cations. The cations build up on the cathode until the desired thickness of metal is achieved. For barrel plating, the “danglers” inside the unit meet the parts to be plated and make up the cathode. For vibratory plating, the “buttons” on the bottom of the unit serve the same purpose.
History of Electroplating
This electrochemical process was invented in 1805 by chemist and inventor Luigi Valentino Brugnatelli. He used a voltaic pile, the first “true” battery, as a source of continuous electricity. The voltaic pile, created five years earlier by Alessandro Volta, was connected by wire to a solution of dissolved gold. A wire was connected to the metal object, which then grounded the circuit. This caused the gold to attach to the surface, producing a desirable, polished finished.
Development of the process slowed down soon afterward. History tells us that the French Academy of Sciences suppressed many of Brugnatelli’s inventions. However, by 1839, scientists in Britain and Russia developed their own electroplating methods. The process then made a significant leap in 1844. At that time, John Stephen Woolrich invented the Woolrich Electric Generator. It was quickly introduced into the process, making it more efficient and attractive for commercial use. Besides being an inventor, Woolrich was credited as a chemist, magneto-plater and gilder, offering his plating and gilding services in a retail setting in England. The electroplating process has been evolving ever since.
Modern day plating specifications call for very specific parameters and tight tolerances, especially for critical applications such as aerospace, medical and electronic applications. For these applications, metal salt concentrations and electrodes are carefully controlled. Precious metal thicknesses need to be precise, which requires bath chemistries to be maintained and deposition rates calculated. Although it started as a rather simple process, electroplating has evolved into a very exacting science.
Illustration Source: The Electro-Plating and Electro-Refining of Metals Arnold Philip, 1911. D. Van Nostrand Company. Fig. 108: "Nickel-plating by Dynamo-electricity"