Gold is one of few metals which doesn’t tarnish, oxidize (rust) or corrode, and as such, it has become a popular metal for jewelry; its durability and everlasting color and shine make it a romantic symbol of everlasting affection.
For other applications, such as circuit boards and electronics, gold is a popular choice because of its excellent conductivity, and its ability to protect underlying layers of base metals from corrosion and tarnishing. Unfortunately, gold’s many uses, as well as its aesthetic value, make it an expensive choice, and its price is hardly stable, making solid gold an unnecessarily pricey option for most applications.
Fortunately, gold plating offers all of the advantages of solid gold, at a fraction of the price.
Gold is one of the most common metals used in both decorative and functional electroplating. A thin layer of gold is deposited onto the surface of another material, typically a base metal like nickel or copper Gold Filled.
Different electroplating methods can be used, depending on the desired results and the type of plating used. For some applications, the gold plating is functional, and needs to be pure and processed a certain way; for others, the gold plating is purely decorative, and can come in a variety of colors and degrees of purity, such as for jewelry.
Plating for jewelry is typically only microns thick, and applied to a base metal such as silver, copper, zinc or nickel. When silver is plated with gold, the silver atoms migrate into the gold layer over time, causing it to change color and tarnish. Barrier layers of metals such as copper or nickel – which also migrate into gold, but much more slowly – are typically used to prevent this process. Nickel is used as a base layer for chrome, because it provides depth and brightness to the finish, and it is used in the same way for gold plating.
Decorative gold plating results in a piece that has the look of solid gold, but which is harder, more durable, and a fraction of the price.
Gold-filled jewelry (also called rolled gold, or rolled gold plate) is another, slightly more durable alternative to gold plating. A base metal, such as brass, is used to construct the piece, and a layer of gold is then applied which is bonded to the base metal with heat and pressure.
This layer is exponentially thicker than typical plating, and lasts for decades.
Almost any metal – silver, copper, brass, etc. – can be used as a substrate for functional gold electroplating. Gold used in these applications needs to be as pure as possible, and its color should be similar to 24-carat decorative gold; otherwise, the conductivity and reflectivity of the plating will be hindered. Just as with decorative gold plating, a barrier layer is often used for functional electroplating to prevent tarnish.
Sound systems, laser reflectors, and circuit boards are just some of the delicate applications for which gold plating is often utilized. Functional gold plating allows the consumer to take advantage of the positive qualities of gold, such as its corrosion resistance, while preserving the advantages of the substrate, and avoiding the cost and softness of solid gold.
Amanda Wood is Managing Director of South Australian Metal Finishing company A Class Metal Finishers Pty Ltd.
A Class is a leading provider of electroplating, metal polishing and other metal surface treatment services.