Gold has always been inherently valuable to mankind, as it is one of few metals which never rusts or corrodes. The seemingly eternal nature of gold makes it extremely popular as a material for jewellery, as it is not only durable but symbolizes a romance that will last indefinitely.
In terms of functionality, it’s also useful for electronics applications, because it is almost unsurpassed in terms of electrical conductivity. In either case, the high and constantly fluctuating price, as well as its softness, causes consumers to try and find alternatives to solid-gold pieces. The most common alternative to solid gold is gold plating.
Many different metals are used in the electroplating process, one of the most common of which is gold. Gold plating is the process of depositing a thin layer of gold onto the surface of another material via the process of electroplating. There are several varieties of gold plating, and different processes are used depending on the intended purpose.
Some plating, such as that used for electronics applications, is functional; other plating, such as plating on jewelry, is purely decorative.
In jewelry-making it’s typically applied to the surface of items that are made of a non-precious base metal, such as silver, nickel, copper or zinc. The unfortunate drawback to gold-plated silver is that silver atoms tend to migrate into the gold, over the months and years, causing it to change color and eventually tarnish. To prevent this, barrier layers of copper and nickel are often used between the silver and gold.
Nickel protects the substrate and increases surface hardness, while also providing depth to the reflectivity gold. Decorative gold plating is a great way to achieve the beautiful look of real gold, without the price tag of solid gold.
Another decorative gold application is gold-filled jewelry, also called rolled or rolled gold plate. Gold-filled jewelry is composed of a base metal, such as brass, coated with a layer of gold that is then bonded to the base metal with the application of heat and pressure.
For functional gold electroplating (electronics or industrial uses), most metal substrates can be used. Silver, copper, brass, aluminum and alloys are all commonly-used substrates for functional gold plating. The gold used for functional applications needs to be as pure as possible, to ensure good conductivity, good reflectivity and high corrosion resistance.
A nickel barrier layer is often applied to functional gold electroplating, similar to decorative gold plating, to prevent tarnishing of the gold. Its color is typically quite yellow, similar to 24-karat solid gold. Functional gold plating is used for radio and electronic components, sound systems, laser reflectors, circuit boards, and other applications in which high electrical conductivity and corrosion resistance are necessary.
In this way, the properties of both the substrate and the gold are combined; for example, the hardness and conductivity of the substrate, with the corrosion and tarnish resistance of the gold.