Gold plating solution has typically been composed of liquid electroplating compounds incorporating the dangerous chemical cyanide bonded to gold in the solution. Alternatives to this include using nitrides of gold that traditionally have proven difficult to synthesize, but now have been improved upon using methods of ion implantation. Barrel and brush mechanical plating are further alternatives to the electro-deposition method traditionally used to plate gold to a surface.
The method chosen for the plating process and which type of gold plating solution is used is determined by what the component that will be plated is to be used for. Gold will tarnish slowly in the presence of infused copper, silver, or nickel atoms that are used as substrates upon which it is plated. Because of this, for jewelry applications, elements that demonstrate the least tendency to migrate into and tarnish the gold, such as copper over silver, are immediately plated under the gold surface. With components used for electrical purposes, where durability is more important, nickel is used as an immediate substrate material to add physical strength to the plating.
Electroplating processes will vary greatly in speed, based both on the concentration of gold in the entire electrolyte compound and the actual chemical composition of the gold plating solution itself. A typical electroplating solution can deposit around one micron of gold on a surface per minute, with layers possible up to 100 microns in thickness. By contrast, forms of electroless gold plating that immerse the part in a nickel-based solution offers more uniform gold coatings with a much longer shelf-life, but a maximum thickness of 10 microns. Immersion solutions also have a much shorter lifespan than typical electroplating solutions, so electroless/immersion technology is typically used to plate fine electrical components. Though electroplating has usually required a conductive surface to plate gold, it is now possible for the plating process to be done on plastic by first etching the plastic and coating it with palladium metal.
Nitride-based gold compounds are another form of gold plating solution. Considered better for electronics applications because of reduced cost and better durability, gold nitride solutions replace the need for bonding gold to toxic elements, such as arsenic and cyanide, and metals such as nickel, cobalt, or iron. The nitrides are generated using an ion gun to implant nitrogen atoms in gold crystals under high vacuum. The resulting gold coating is harder than traditional industrial plating and doesn't possess any toxic elements that can damage the environment when the component is disposed of later. Research into additional types of gold plating solution continues to develop to eliminate the practice of using toxic metal alloys that can potentially pollute groundwater when old electrical components are disposed of in landfills.
