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Gold electroplating involves bonding a thin layer of gold to an object using an electrolyte solution containing dissolved gold compounds and catalyst chemicals. The object is connected to the cathode and anodes, made of metal, are immersed in the solution. The process takes a few minutes and thicker layers may take longer. To prevent the base metal from migrating through the gold layer, copper or silver items are often electroplated with another metal first.
Gold electroplating is a process in which an electric current is used to bond an extremely thin coating of gold to an object made of another metal. Circuit elements called cathodes and anodes and an acidic solution called an electrolyte solution, containing dissolved gold compounds and catalyst chemicals, are used to create the coating, which can be a few microns thick. A tank of inert material such as glass or plastic is used to contain the solution.
The electroplating process begins with the preparation of the electrolytic solution. For gold plating, the chemical bath will mainly consist of water, acidified by the addition of phosphoric acid. Gold, in the form of gold chloride, is added to the solution. Catalysts such as potassium cyanide can also be used. They aid in the transfer of the gold ions to the object being plated and increase the conductivity of the solution which is important, as it is the current flow through the solution that creates the reaction which bonds the gold to the target object.
The object to be plated is connected to part of an electrical circuit, called the cathode. The cathode is analogous to the positive terminal of a battery. As the gold salt compounds in the electrolyte solution deposit gold on the target object, they lose electrons which form the electric current.
The other end of the circuit is called the anode and is made of metal. The anode is analogous to the negative terminal of a battery and current flows from the anode into the electrolyte solution. For many types of electroplating, the anode consists of the same metal deposited on the target object. For electroplating gold, the anodes are usually stainless steel, graphite, specially treated titanium, or a metal called columbium, although other metals may sometimes be used. The cathode with the target object and the anode are immersed in the electrolyte solution and current is introduced.
Gold plating usually only takes a few minutes. Thicker layers of gold may take longer. As a gold-plated object ages, atoms of the underlying metal can gradually mix and migrate through the gold layer to the surface, a process that can take many years. Copper and silver are notorious for this phenomenon. For this reason, copper or silver items that are to be electroplated with gold are often electroplated with another metal first, such as nickel, which prevents the base metal from migrating into and through the gold layer at the surface.
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