Artisans have been creating precious metal surfaces using metal plating for centuries. Today, metal plating is used for both decorative and functional purposes. Read on to learn more about the history and process of metal plating and how artists, engineers, and designers have used throughout the years.
The History of Metal Plating
Metal plating evolved from earlier processes such as fire gilding and gold leafing, which used small amounts of gold to cover large surface areas. In gold leafing, paper thin sheets of gold are affixed to a surface such as wood or metal with a tacky glue, and are burnished onto the object, to create a lustrous gold appearance.
In fire gilding, thin plates or fine grains of gold are thrown onto hot mercury, which when stirred with an iron rod, are absorbed. The mixture is squeezed through a sheepskin to separate the heavier gold from the mercury, resulting in a buttery amalgam that can be spread onto the surface of a mercury-coated object. When heat is applied, the mercury burns away, resulting in a beautiful gold coating.
The Discovery of Electroplating
Similar to other ancient processes, metal plating deposits a thin layer of a precious metal across the surface of another metal. Today’s metal plating uses an electromagnetic or chemical process to fuse a precious metal to another, less expensive metal, most commonly silver, zinc, chrome, or brass. This technique is used to create electronic parts, as well as fine jewelry and other art objects.
Luigi Brugnatelli, an Italian chemist, first achieved modern electroplating in 1805. However, his successful attempt at plating silver with gold was kept secret by the French Academy of Sciences, and the technique remained unknown until it was rediscovered by independent Russian and English scientists decades later. Electroplating later became industrialized in the 1940s, resulting in the mass production of silver plated utensils, brushes, teapots, and more.
Although modern electroplating techniques were not developed until the 19th century, there is evidence that pre-Colombian metalsmiths working in ancient Peru gilded metal using electrochemical processes. A variety of sophisticated gilded relics were found in Sipán, which date back to 50 AD. These earliest examples of metal plating are attributed to the Moche people.
Metal Plating Process
Before metal is plated, it is first cleaned in a chemical bath, and sandblasted so that the metal plating can adhere to the rougher surface. The metal object is then hung on a copper wire support frame, which functions as an electrical current.
A vat is prepped for the object with electrically conductive water and chemicals, and lined with balls or bags of the plating metal. The plated object is connected to a positive electric terminal, while the copper support frame it rests on is connected to the negative terminal. As approximately six volts of electricity flow through the tank, the plating metal dissolves, and the metal ions travel through the tank to adhere to the surface of the negatively charged metal object.
Now the object is covered in a thin layer of the plating metal. Plating can take anywhere from a few minutes to several hours, depending on the thickness you wish to achieve. The plated object is finally soaked in another chemical bath and rinsed with hot water to remove residue and prevent rust. At MKM Jewelry, your premier silver, rhodium, and gold plating service in Los Angeles, our highly trained technicians have years of training with these processes.
An Alternate Process
Metal plating can also be achieved through an autocatalytic process, known as electroless plating or conversion coating plating. The plating process is set up similarly, but instead of using an external energy source, the metal’s reaction is triggered by a reducing agent, such as sodium hypophosphite. The trigger releases hydrogen, creating an electrical charge. This method does not require an electrical current but is more difficult to control.
Tools Used in Metal Plating
Metal plating requires an array of chemicals, which vary depending on the base metal and the plating metal. Since the metal plating process occurs within a vat that can be charged with an electrical current, additional vats are often needed for the chemical and water baths following the plating process.
At home metal plating kits are available, although the complexity of the process and the toxicity of the required chemicals make DIY metal plating a daunting task. When it comes to plating metal, it is best to leave it to the professionals, like MKM Jewelry. We offer gold plating services in Los Angeles for jewelry designers looking to cut costs and save money when testing new designs or creating fashion jewelry.
Types of Plating Styles
Metal plating can be performed in a variety of ways. Metal can be plated by hand in small batches by a trained technician, or can be done in a fully automated factory setting.
Other types of metal plating include barrel plating, which is primarily used for small parts that do not require great precision. In barrel plating, the plating process is performed within a large barrel, which accommodates high rinse and pull out rates.
Many fabricators may also choose to use the rack plating technique, in which the metal to be plated is hung on a rack, helping the craftsmen control the time flow of the metal plating process.
Common Plating Metals and Uses
Numerous types of metals can be used in metal plating, including chromium, cadmium, silver, gold, rhodium, brass, bronze, and zinc.
Metal plating is used for both artistic and industrial purposes. In fine jewelry, gold, rhodium, and silver plating are most commonly used to create genuine precious metal surfaces without the cost of producing items that are made entirely of solid gold or silver.
In the electronic parts industry, gold is also frequently used and highly valued for its corrosion resistant and conductive properties. Gold plated copper parts are frequently used in circuit boards and microchips. Electroplating is even used by NASA to gold plate thermally controlled spacecraft instruments due to the fact that gold reflects 99% of infrared wavelengths.
One of the most useful applications of metal plating is preventing corrosion. By plating corrosive metals with a more stable metal, such as gold, you can increase the longevity and durability of an object. Plated metals are tested for their ability to defy corrosion with a variety of environmental corrosion tests, which simulate the passing of time.
Acetic Acid Salt Spray Test
Specific environmental corrosion tests include the Acetic Acid Salt Spray Test, where metals are misted with an acetic acid to accelerate corrosion. The same test can also be performed with additional copper salts added.
In the Corrodkote Test, electroplated pieces are coated with kaolin, which contains aluminum chloride, copper nitrate, and ferric chloride, and then placed in a humidity chamber.
Electrochemical Corrosion Test
Technicians can also simulate corrosion in mere minutes with an electrochemical corrosion test, where an anodic material is placed in an electrolyte. Sulfur dioxide is also used to test for metal’s defense against corrosion.
Potential Tarnishing Issues
When gold is plated onto silver, the silver ions and gold ions leach together over time, resulting in a faded, tarnished surface. To prevent this, silver is usually plated first in nickel, before being plated in gold, to create a barrier between the gold and silver ions.
Copper and gold atoms are also liable for diffusion, so most copper electronic parts also use nickel as a barrier metal between the copper and gold. When you electroplate in this way, you can create a flawless, high quality metal plated surface.
Working with the Best
Metal plating is a fascinating process that produces beautiful effects with a myriad of uses — ranging from practical to aesthetic. MKM Jewelry offers professional gold plating services in Los Angeles to help you bring your jewelry and industrial designs to life. MKM Jewelry offers silver, gold, rose gold, and rhodium plating, so bring your pieces in for plating today.