Precious Metal Electroplating

You may have wondered how manufacturers bond precious metals to other materials. A process known as precious metals plating is used to make the metal adhere to an underlying object, which is called a substrate. The plating of precious metals is a complex process that requires immersing the substrate into a special chemical solution containing dissolved ions of the precious metal and then introducing an electric current into the solution to deposit the metal onto the surface.

At Sharretts Plating Company, we can provide specialized precious metal plating services for a wide range of industrial purposes. Read on to learn more about the many uses of precious metals in electroplating and the vast array of precious metal compounds we can assist you with.

What Exactly Are Precious Metals?

Precious metals are naturally occurring chemical elements known for their rarity, high economic value and lustrous appearance. They are not as reactive as base metals, which are more common and less economically valuable, so they don't oxidize nearly as quickly. They're also relatively malleable. Their high economic value comes from their rarity and usefulness in various applications.

Precious metals are commonly used in the minting of bullion coins and the manufacturing of fine jewelry, but they have many industrial uses as well. Gold, silver and platinum are the most widely recognized precious metals. The platinum family also includes: 

• Rhodium
• Palladium
• Iridium
• Osmium 
• Ruthenium

Various alloys, especially those containing palladium, also have uses across a range of industries.

Precious Metal Use in Electroplating

Precious metals exhibit many properties that make them valuable for use in a wide variety of industrial electroplating processes. Many of these metals offer superior resistance against corrosion and wear and are highly ductile and conductive. Their inherent luminescence makes plating with these metals a popular option. Precious metal plating is typically more expensive than other metal types, although the superior quality can usually offset the relatively high cost over time.

The availability of a specific metal can also have an impact on the actual cost of precious metal plating services. The more readily available a metal is at a given time, the less expensive the services are likely to be.

Precious Metal Plating Services Available From Sharretts Plating Company

Sharretts Plating Company offers a wide range of precious metal plating services that have been perfected over more than eight decades of extensive research, design and implementation. Our services include the following.

Gold Plating

Typically viewed as the most effective plating solution, gold plating is usually the best choice when cost concerns are minimal. It is highly resistant to corrosion even in extreme environments, provides superior protection against high heat, and serves as an excellent conductor of electricity. The look of gold also contributes to its popularity.

Because of its conductivity, gold plating is popular in the electronics industry and is frequently used in the production of electrical components such as switches and connectors and as a semiconductor for circuit boards. Its heat resistance makes it useful in the aerospace industry as well. You also see gold used in various medical and dental applications, such as the production of false teeth and surgical tools.

Silver Plating

While silver is not as resistant to corrosion as gold, it still offers excellent protection from it as well as from acids and chemicals. It also provides outstanding thermal and electrical conductivity and a famously attractive appearance.

Silver is less expensive than gold, platinum and palladium, and is frequently used as an alternative to these other precious metals when seeking to reduce costs. It can also easily be alloyed with other metals. These characteristics make silver one of the most popular metal plating materials. It has uses in many different industries, including:

• Automotive
• Telecommunications
• Electronics 
• Electricity generation 

Before applying silver plating, it's essential to prepare the substrate by minimizing tensile stress and imperfections and applying an undercoating of copper, nickel or both. You must complete any required mechanical or thermal treatments before beginning the silver plating process. You might also choose to apply an anti-tarnish coating.

Platinum Plating

Platinum is an extremely rare metal and has a variety of useful characteristics. Although it is 15 times rarer than gold, it's present in about 20 percent of all consumer products.

It has an even higher melting temperature than gold, which enhances its durability and makes it ideal for aerospace and automotive applications. Its ability to absorb hydrogen also makes it especially useful in the auto industry. It resists corrosion and damage from contact with water, chemicals, acids and other substances extraordinarily well. Platinum is ductile, making it suitable for a range of complex uses. Other useful attributes include its: 

• Electrical conductivity
• Magnetizing capabilities
• Adhesion promotion capabilities

As mentioned earlier, the platinum family of metals includes rhodium, palladium, iridium, osmium and ruthenium.

Rhodium Plating

Another platinum-family metal, rhodium is extremely rare and highly valued for its durability. It's useful for a range of applications due to characteristics such as its resistance to oxidation, corrosion and acids, even under extreme heat or conditions with high levels of moisture. It's also exceptionally hard and dense and has a melting point even higher than that of platinum. It has low electrical resistance, low contact resistance and a silvery-white appearance.

Because of its ability to reduce nitrogen oxide levels in exhaust gases, manufacturing catalytic converters is the most common use of rhodium. The introduction of the three-way catalytic converter in the 1970s enabled the use of rhodium instead of platinum or palladium, increasing the demand for this precious metal. Today, approximately 80 percent of the rhodium used for industrial purposes goes toward the production of catalytic converters for automobiles. Other applications include: 

• Optic fibers
• Optical mirrors
• Thermocouple elements 
• Electrical contact material

Ruthenium Plating

Another precious and platinum-group metal used for electroplating is ruthenium. It is valued for its ability to enhance durability in a range of conditions. It's chemically inert, like all platinum-family metals, and is impervious to acids of any temperature or aqua regia, which is a combination of hydrochloric and nitric acid. Adding potassium chlorate to a solution that contains ruthenium, however, can spark oxidation. 

Manufacturers also often choose ruthenium when they want to gain a certain appearance. It naturally has a shiny gray-white color but, by modifying the plating bath, you can create a darker gray or black coating. Room-temperature ruthenium won't tarnish. Another attractive attribute of ruthenium is its cost. Although it is rare, it is relatively affordable, especially when compared to similar metals. 

Ruthenium is often used to produce wear-resistant electrical contacts and data storage products such as microchips, semiconductors and read elements for hard disc drives.

Palladium Plating

Those searching for a cost-effective alternative to gold plating may consider palladium plating, offering comparable corrosion resistance. It is more susceptible to stress than gold, however. 

Palladium has many characteristics that make it similar to other platinum family metals but has a lower density than the rest of the group. Palladium offers excellent resistance to corrosion and wear. It is more malleable than platinum but more susceptible to damage caused by strong acids and may discolor under high temperatures.

Palladium is known for semi-bright, silvery blue appearance and is often used in the automotive industry in the production of catalytic converters. You can also find palladium in various consumer electronics and medical devices. We’re also capable of performing precious metals plating using palladium alloys.

Palladium-Nickel Plating

One of the challenges in using pure palladium for plating is its susceptibility to cracking due to its high stress. Alloying palladium with nickel reduces this stress, which is especially useful in heavy wear situations. It also reduces porosity, provides excellent corrosion and heat resistance, and is readily solderable. 

Because of its low-contact resistance, it commonly sees use in the electronics industry for plating contacts and connectors. Palladium-nickel also serves as an ideal barrier between base metals.

A typical palladium-nickel alloy contains a palladium deposit of 70 to 80 percent. Manufacturers sometimes also apply a thin layer of gold on top of a palladium-nickel coating, which provides the look of gold at a much lower cost, along with the attributes of palladium-nickel. 

Palladium-Cobalt Plating

This relatively new precious metal plating process is gaining widespread acceptance for use in the manufacturing of electronic devices such as cell phones and laptop computer batteries. It also sees use in the production of semiconductors.

Alloying palladium with cobalt increases its hardness and its density, making it more durable. It also offers excellent corrosion resistance, electrical conductivity and low contact resistance. It has useful magnetic properties.

It sometimes serves as a lower-cost alternative to gold plating. In some situations, using a palladium-cobalt alloy instead of gold can reduce precious metal costs by 90 percent. 

Precious Metal Plating Processes

At SPC, we offer rack and barrel electroplating and follow best practices for all projects we undertake. Although the specifics differ depending on factors such as the metal used, the substrate material and the desired outcome, here's an overview of the processes we use for plating with precious metals.

Preparation for Plating

Before we plate an object, we ensure that it is adequately cleaned and prepared so that the outcome is optimal. First, we check that the substrate is free of defects or stress that could impact the quality of the plating. We then clean it using a variety of methods, including: 

• Preheating
• Polishing
• Ultrasonic cleaning
• Steam cleaning 
• Electro-cleaning

Depending on the materials used, we might apply other thermal or mechanical operations or treatments. Under some circumstances, we also apply an under-plating. If plating with silver, for example, we will apply an undercoating of copper, nickel or both. We might also use an anti-tarnish coating.

Electroplating

The electroplating process involves placing the substrate in a liquid electrolyte solution that contains dissolved ions of the metal to be plated and other chemicals. Passing a DC electric current through the precious metal electrolyte solution causes the metal ions to attach to the object's surface and form a metal coating. This phenomenon is known as electrodeposition. 

Plating may occur via the rack or barrel plating methods: 

• The rack method involves hanging the items on a rack using metal hooks, which you then submerse into the plating solution. The hooks provide the electrical current. 
• In the barrel process, we place the substrate in a barrel-shaped cage, which we submerge into the plating bath, where a slow tumbling movement initiates the plating.

Other factors to consider include the substrate used, the voltage applied, the length of the process and the temperature of the plating bath. All of these aspects influence the outcome of the process, including the thickness, color and quality of the plating. It's also crucial to ensure that the bath stays free of contaminants.

Finishing

After electrodeposition occurs, we may use other processes to finish the piece. Applying a heat treatment can remove excess trapped hydrogen. Rinsing, steam cleaning or other methods can remove any residue, after which we may heat dry the piece. If desired, we can also add secondary plating coatings.

Is Precious Metal Plating the Right Solution for Your Manufacturing Operation?

As a rule of thumb, the superior quality makes plating with precious metals the best choice for many industrial and manufacturing operations. However, if the cost is prohibitive for your company, you can often achieve comparable results with less-expensive metals, such as tin, nickel or copper. Alloys of these metals can also offer enhanced plating performance while still helping to minimize your costs. If you choose to use precious metal, however, its superior quality will make the larger upfront investment worthwhile over the long run.

Precious metals are known for various attractive and useful properties, including their conductivity, their ductileness, their luminescence and other qualities, and their chemical inertness and resistance to corrosion, heat and wear.

Although precious metals have many characteristics in common, they also have some variations in their properties. The qualities you want your plating to have will influence your decision of what type of metal to use:

• Gold is typically the best choice unless its cost is too high. It has excellent conductivity, corrosion resistance and heat resistance.
• Silver is less expensive than gold and offers excellent conductivity and resistance to chemicals and acids,. 
• Platinum has a high melting point and the ability to absorb hydrogen as well as excellent resistance to corrosion.
• Rhodium is exceptionally hard, dense and resistant to heat. It also resists corrosion well and has a low contact resistance.
• Ruthenium is valued for its durability and resistance to acids.
• Palladium is another popular alternative to gold and offers outstanding corrosion and wear resistance.
• Palladium-Nickel is less likely to crack than pure palladium, provides corrosion and heat resistance, has a low contact resistance and is readily solderable.
• Palladium-Cobalt is more durable than pure palladium and offers excellent corrosion resistance and electrical conductivity as well as low contact resistance. It's another suitable alternative to gold.