Electroplating Explained - How It Works, Types, Benefits & ...

Electroplating is a common surface finishing process in the manufacturing industry to coat a material (substrate) with another metal. In recent years, the process has undergone many advances, making it much more accurate and capable of working with a wider range of materials.

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In this article, we will explore the modern electroplating process to understand what it is, how it works, its benefits and limitations.

What Is Electroplating?

Electroplating is a manufacturing process in which a thin layer of metal atoms is deposited to another material through electrolysis. The metal added is known as the deposition metal, and the underlying material or workpiece is known as the substrate material.

By adding a layer of the desired metal, we can improve several physical, mechanical and chemical properties of the substrate, such as its strength, heat conductivity, electrical conductivity, abrasion and corrosion resistance.

Improving these properties can allow us to combine different metals to achieve properties that perfectly suit different applications.

How Does the Electroplating Process Work?

The electroplating process works on the principle of the electrolytic cell.

In this process, two metal rods are placed in an electrolyte. The rods act as electrodes when connected to the opposite terminals of a battery or power supply to create a potential difference. The electric current causes the electrolyte bath to disintegrate into dissolved metal ions, and the positively charged metal ions deposit on the negative electrode (cathode).

These positively charged ions are part of the electrolyte. As they get deposited on the cathode, their concentration in the electrolyte reduces. By choosing a suitable element for the anode, we can replenish the concentration of the positive ions.

For instance, if we need to coat brass with copper, the brass becomes the substrate. Connecting it to the negative terminal makes it the cathode. We use an electrolyte, such as a copper sulfate solution, that gives positive copper ions upon disintegrating. On the other end, we use a copper anode to replenish the electrolyte&#;s positive ions.

We can control the plate thickness, rate of metal deposition, surface finish, colour and many other factors by manipulating the process parameters. For example, using pure copper plates will give a better appearance than regular copper rods available in the market.

Using this process, the material can be coated with one or more metals.

Types of Electroplating Methods

Over the years, the electroplating process setup has evolved to suit different applications. By choosing a method in line with the application, the efficiency of the operation can be increased significantly.

To choose the right one, we must first understand the different types. Overall, electroplating methods can be divided into four major types. These are:

1. Mass plating

2. Rack plating

3. Continuous plating

4. In-line plating

Mass Plating

Barrel plating

As the name suggests, mass plating is used for mass-production applications. The method can handle a large volume of products that require thin coatings of metal.

A common type of mass plating method is known as barrel plating. In this method, the material to be coated (substrate) is dipped in a barrel containing the metal salt (electrolyte) and the anode of the coating metal.

The barrel plating setup is highly economical for small parts that need a uniform coating. As the barrel rotates, all the parts are cleaned, descaled and uniformly coated to a greater extent compared to rack plating.

This method is not recommended for parts that require a detailed finish without scratches and entanglement.

Mass plating is generally used for small but robust parts such as nuts, bolts and screws.

Rack plating

Rack plating

When the parts are larger than those suitable for mass plating, the rack plating method is used. In rack plating, the parts are mounted on racks and immersed in the chemical electroplating bath.

The rack plating process reduces the damage to delicate or fragile parts and coats the interior contours and deep crevices of parts, unlike mass plating.

This process is, however, more expensive than mass plating. But it makes up for it by providing a plated layer of much higher quality than a mass-plated product.

Rack plating is typically best for large, fragile and complex parts that require a plating of gold, silver, tin, copper or nickel.

Continuous plating

The continuous plating process is performed on exceptionally long parts, such as metal tubes, wires and strips.

In the case of thin strips, this process is also known as the reel-to-reel plating process. In this process, a long product is passed through the chemical bath at a specified rate. The end product&#;s quality is controlled by manipulating the process parameters and the time spent in the bath.

The reel of the product to be coated is uncoiled at the initial station, and once it passes the electrolyte/anode and gets coated, it is recoiled for easier storage and transport. Then further operations can be performed to stamp it into the required shapes.

In-line plating

The in-line plating method uses an assembly line for the metal plating operation. The metal passes through the various stations and automated machinery facilitates the chemical reaction.

Line plating is generally used for coating copper, zinc, chromium and cadmium. A variety of substrates can be coated with these metals through line plating. This method is relatively cheaper than other methods because a lower amount of chemicals is needed per piece.

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Suitable Materials

Electroplating is a versatile process owing to the fact that it requires only one property in the substrate: electrical conductivity.

Since this property is exclusively available with metals (barring a few exceptions), we could initially use electroplating only for metals. But with the advent of conductive sprays and coatings, it is now possible to coat non-conducting materials such as plastic and wood too.

As a result, today, there are many more materials that can be electroplated. The substrate material can greatly vary depending on the application.

Silver or gold plating is often used to improve the appearance. To improve properties such as bacterial resistance and conductivity, copper plating is a favourite. Copper electroplating also offers increased malleability, lubricity and corrosion resistance.

Similarly, when we need to improve corrosion and wear resistance simultaneously, we go for nickel plating. Nickel also improves the appearance of the product.

Some other metals that are normally used for coating in electroplating are chromium, cadmium, zinc, iron and titanium.

But the substrate and the coating must be chosen carefully. Not all materials combine with each other. For example, steel cannot be plated with silver right away. It must first be plated with copper or nickel before silver plating.

Benefits

The first modern electroplating plant was set up in Hamburg in the late 19th century. The intention was to improve the appearance. But as science understood the mechanism and benefits of electroplating, its applications for non-decorative purposes became common.

Today, we understand the true breadth of electroplating benefits. Let&#;s list them down for a better overall understanding.

Improved physical properties (colour, lustre, conductivity, low weight)

Electroplating improves physical properties such as colour, lustre and conductivity.

Colour and lustre provide cosmetic upgrades that are necessary for many day-to-day products as well as art applications.

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Everyday appliances and kitchen products such as utensils, pans, cutlery, taps, kettles and other gadgets become much more attractive when coated with shinier metals such as copper, gold or silver. It also improves their functionality, as electroplated products are often easier to clean.

The appearance of artistic installations such as sculptures and figurines can also be improved by using electroplating. As a result, electroplating also finds use in art restoration and preservation projects besides new art creation.

Functionality can also receive a boost in technical applications involving electrical components such as antennas and integrated circuits. Although metals are already conductive, coating them with a better conductor improves the overall conductivity of the part while keeping costs low.

Costs are also reduced by the fact that non-metals can be used for electrical applications after electroplating. Besides having lower costs, non-metals also weigh less, which reduces the cost and difficulty related to the transport and storage of products.

Improved mechanical properties (tensile strength, bending strength, abrasion resistance, surface finish)

Electroplating also improves mechanical properties such as tensile strength, wear resistance and durability, depending on the application.

The small increase in tensile strength is enough to bridge the gap between the SLA resins of 3D printing (plastics) and metal alloys. The distinct strength characteristics allow the use of electroplated materials in applications where previously metals would have had to be used.

The metal skin on a plastic product, besides making the product lighter, also imparts excellent flexural strength characteristics.

We can also improve the surface finish using electroplating. This makes the products easier to handle and reduces friction.

All these improvements increase the short-term performance while also lengthening the lifespan of the products.

Improved Chemical Properties (Corrosion, Chemical, UV and Radiation Resistance)

The chemical properties of a material can also be enhanced by using electroplating. Properties such as corrosion resistance, resistance to chemicals and UV light are crucial in certain applications such as medical implants.

Typically, medical implants depend on precious metal coatings of gold, silver, platinum and copper for their corrosion protection, electrical conductivity, heat dissipation, non-toxic and antibacterial nature.

Chemical and corrosion-resistant products are also required for harsh service environments where the product is exposed to chemicals, moisture and seawater.

Limitations

Electroplating has certain disadvantages that prevent its use in some cases. Let&#;s evaluate these to get a complete picture.

Complex process

The process is far from simple and can be difficult to carry out reliably. A process would have to be set with predetermined parameters to obtain parts of a consistent quality. Mistakes in preparation and pretreatment can lead to defects, poor quality and capability of finished parts.

Electroplating cannot be used for all material combinations, as they may not combine well with the plating solution.

Long plating time

The plating time can be excessively long in some cases. The metal deposition rate can be increased by either increasing the power supply or the concentration of the electrolyte or both. But this will cause uneven deposition, which can be a dealbreaker in some cases.

The benefits are limited to the surface

By its nature, electroplating is only limited to the surface. Once the surface layer is scratched off, the product can lose some or all of the benefits provided by the process.

Hazardous nature

The process releases gases due to the reduction at the cathode. If these gases are of a hazardous nature, they pose considerable risks for personnel in the vicinity.

Hexavalent chromium exposure from chrome plating is an apt example of how hazardous the electroplating process can be.

Wrapping It Up

Electroplating is nothing short of an engineering wonder. In the past, we could only use it on metals, but that is no longer the case. Today, we can electroplate plastics, ceramics and even organic materials such as leaves and flowers.

However, it still remains a very difficult process to execute consistently. This is why engineers and designers should turn to electroplating service providers for their expertise. Fractory&#;s sales engineers have plenty of experience in planning and executing custom projects, so don&#;t hesitate to get in touch.

FAQ

How do I identify the positive and negative terminals of the power supply in the electroplating solution?

It is very important to maintain the right polarity during electroplating. If for some reason you are not able to identify the anode (positive electrode) from the cathode (negative electrode), remember that the bubbles are generated on the cathode during the reaction.

This tells us that the electrode with the bubble formation is connected to the negative terminal of the power supply.

What is the difference between electroplating and electropolishing?

Electropolishing is basically the reverse operation of plating. Instead of adding material, electrochemical polishing removes it. In the electropolishing process, the workpiece is the anode, contrary to electroplating, where the workpiece is the cathode. Thus, electropolishing is also known as the reverse plating process.

What is electroless plating?

Electroless plating works on the principle of an electrochemical cell. A chemical reaction causes the deposition of one material on another without the need for an electric current. The coating metal is usually a metal or a metal alloy and the substrate could be either a metal or non-metal such as plastic, ceramic, glass, etc.

What is electroforming?

The electroforming process refers to the use of electric current across a chemical bath to form solid models with intricate cavities. The process is similar to electroplating except that instead of a surface, we are building a solid article with a complex cavity.

It uses a template known as the mandrel. The mandrel is dipped in the electrolyte and the electrolytic reaction forms a layer of the deposition metal on the mandrel in the negative shape of the mandrel.

While electroplating may seem like advanced technology, it is actually a centuries-old process. The very first electroplating experiments occurred in the early 18th century , and the process was officially formalized by Brugnatelli in the first half of the 19th century. After Brugnatelli&#;s experiments, the electroplating process was adopted and developed across Europe. As manufacturing practices advanced over the next two centuries through the Industrial Revolution and two world wars, the electroplating process also evolved to keep up with demand, resulting in the process Sharretts Plating Company uses today.

Electroplating is also known as electrodeposition. As the name suggests, the process involves depositing material using an electric current. This process results in a thin layer of metal being deposited onto the surface of a workpiece called the substrate . Electroplating is primarily used to change the physical properties of an object. This process can be used to give objects increased wear resistance, corrosion protection or aesthetic appeal, as well as increased thickness.

Electroplating is a popular metal finishing and improving process used in a wide range of industries for various applications. Despite the popularity of electroplating, however, very few outside of the industry are familiar with the process, what it is and how it works. If you&#;re considering using electroplating in your next manufacturing process, you need to know how the process works and what material and process options are available to you.

ELECTROPLATING PROCESS

The electroplating process uses an electric current to dissolve metal and deposit it onto a surface. The process works using four primary components:

• Anode: The anode, or positively charged electrode, in the circuit is the metal that will form the plating.
• Cathode: The cathode in the electroplating circuit is the part that needs to be plated. It is also called the substrate. This part acts as the negatively charged electrode in the circuit.
• Solution: The electrodepositing reaction takes place in an electrolytic solution. This solution contains one or more metal salts, usually including copper sulfate, to facilitate the flow of electricity.
• Power source: Current is added to the circuit using a power source. This power source applies a current to the anode, introducing electricity to the system.

Once the anode and cathode are placed in solution and connected, the power supply supplies a direct current (DC) to the anode. This current causes the metal to oxidize, allowing metal atoms to dissolve in the electrolyte solution as positive ions. The current then causes the metal ions to move to the negatively charged substrate and deposit onto the piece in a thin layer of metal.

As an example, consider the process of plating gold onto metal jewelry. The gold plating metal is the anode in the circuit, while the metal jewelry is the cathode. Both are placed in solution and DC power is supplied to the gold, which dissolves in solution. The dissolved gold atoms then adhere to the surface of the base metal jewelry, creating a gold coating.

While this process is constant, three factors can impact the quality of the plating. These factors are the following:

• Bath conditions: Both the temperature and the chemical composition of the bath impact how effective the electroplating process is.
• Part placement: The distance the dissolved metal needs to travel will affect how effectively the substrate is plated, so the placement of the anode relative to the cathode is important.
• Electrical current: Both the voltage level and the application time of the electrical current plays a role in the efficacy of the electroplating process.

Learn about more factors that affect electroplating.

WHICH METALS ARE USED IN THE ELECTROPLATING PROCESS?

Plating can occur with individual metals or in various combinations (alloys) that can provide additional value to the electroplating process. Some of the most commonly used metals for electroplating include:

• Copper: Copper is often used for its conductivity and heat resistance. It is also commonly used to improve adhesion between layers of material.
• Zinc: Zinc is highly corrosion-resistant. Often, zinc is alloyed with other metals to enhance this property. For example, when alloyed with nickel, zinc is particularly resistant to atmospheric corrosion.
• Tin: This matte, bright metal is highly solderable and corrosion resistant as well as environmentally friendly. It is also inexpensive compared to other metals.
• Nickel: Nickel offers excellent wear resistance, which can be improved through heat treatment. Its alloys are also very valuable, offering elemental resistance, hardness and conductivity. Electroless nickel plating is also valued for its corrosion resistance, magnetism, low friction and hardness.
• Gold: This precious metal offers high corrosion, tarnish and wear resistance and is coveted for its conductivity and aesthetic appeal.
• Silver: Silver is not as corrosion resistant as gold, but it is highly ductile and malleable, has excellent resistance to contact wear and offers excellent aesthetics. It is also an alternative to gold in applications where thermal and electrical conductivity is needed.
• Palladium: This bright metal is often used instead of gold or platinum for its hardness, corrosion resistance and beautiful finish. When alloyed with nickel, this metal achieves excellent hardness and plating quality.

Price, substrate composition and desired result are key factors when determining the most appropriate electroplating material for your application.

There are several different plating techniques available, each of which can be used in various applications. Some of these types of electroplating are described in more detail below:

• Barrel plating: Barrel plating is a method used to plate large groups of small parts. In this process, parts are placed inside a barrel filled with an electrolyte solution. The electroplating process proceeds while the barrel is rotated, agitating the parts so that they receive consistently even finishes. Barrel plating is best used on small, durable parts, but offers a cheap, efficient and flexible solution.
• Rack electroplating: Rack or wiring plating is a good option if you need to plate large groups of parts. In this method, parts are placed on a wire rack, allowing each part to come into physical contact with the electrical power source. Though more expensive, this option is optimal for more delicate parts that cannot undergo barrel plating. It is important to note that rack plating is more difficult for parts that are sensitive to electricity or have an irregular shape.
• Electroless plating: Electroless plating, also known as autocatalytic plating, uses a similar process as electrodeposition but does not directly apply electricity to the part. Instead, the plating metal is dissolved and deposited using a chemical reaction in place of an electrical one. While this option is useful for parts that are incompatible with electrical currents, it is more costly and less productive than other options.

While these methods accomplish electrodeposition in different ways, they all use the same basic principles.

USES OF ELECTROPLATING

While electroplating is often used to improve the aesthetic appearance of a base material, this technique is used for several other purposes across multiple industries. These uses include the following:

• • Build thickness: Electroplating is often used to build up the thickness of a substrate through the progressive use of thin layers.

• Protect substrate: Electroplated layers serve as sacrificial metal coatings. This means that when a part is placed in a harmful environment, the plated layer breaks down before the base material, protecting the substrate from damage.
• Lend surface properties: Electroplating allows substrates to benefit from the properties of the metals they are plated with. For example, some metals protect against corrosion, improve electrical conductivity, reduce friction or prepare a surface for better paint adhesion. Different metals lend different properties.
• Improve appearance: Of course, electroplating is also commonly used to improve the aesthetic appearance of a substrate. This can mean plating the substrate with an aesthetically pleasing metal or simply applying a layer to improve surface uniformity and quality.

BENEFITS OF ELECTROPLATING

Electroplating offers a range of benefits for components. Some of the specific benefits of electroplating include the following:

• • Protective barrier: Electroplating creates a barrier on the substrate, protecting it against environmental conditions. In some cases, this barrier can protect against corrosion caused by the atmosphere. This property specifically benefits components because the parts last longer in more harsh conditions, meaning that they need less frequent replacement.
  • Enhanced appearance: Exterior pieces are often plated with thin layers of precious metals to make them more lustrous and attractive to look at. This plating lends aesthetic appeal without exorbitant costs, meaning that attractive parts can be sold at lower prices. Additionally, electroplating is often used to prevent tarnishing on silverware, improving longevity and aesthetic appearance over time.
  • Electrical conductivity: Silver and copper plating help improve electrical conductivity in parts, offering a cost-effective, efficient solution for improving conductivity in electronics and electrical components.

• Heat resistance: Several metals, including gold and zinc-nickel, are resistant to high temperatures, improving the ability of the substrate to resist heat damage. This, in turn, can improve the lifespan of plated parts.
• Improved hardness: Electroplating is often used to improve the strength and durability of substrate materials, making them less susceptible to damage from stress or rough use. This quality can help increase the lifespan of plated parts, reducing the need for replacement.

Some benefits offered are metal-specific. For example, nickel plating is useful for reducing friction, which helps to reduce wear and tear and improve part longevity. Zinc-nickel alloys, on the other hand, are used to prevent the formation of sharp protrusions during manufacturing, which can result in part damage. Copper is also specifically used as an undercoating in many applications, as it facilitates adhesion with additional metal coatings to improve the surface quality of the final part.

INDUSTRIES THAT USE ELECTROPLATING

Whether your company is looking for corrosion protection, improved durability or increased electrical conductivity, electroplating offers solutions. That&#;s why electroplating is widely used across a variety of industries. Listed below are some of the industries SPC serves and how they apply electroplating:

• • Automotive industry: Plating is commonly used in the automotive industry to prevent corrosion in harsh environmental conditions. Zinc-nickel plating solutions help prevent rust formation, while electroless nickel plating serves as a great alternative for chrome on catalytic converters and plastic parts.
  • Electronics industry: Electronics companies often use gold plating for its conductivity, applying it to semiconductors and connectors. Gold is also coveted for its corrosion resistance in this industry. Copper plating is another commonly used metal in this industry, used as an alternative to gold when the focus is on conductivity. Palladium alloys are also commonly used as protective coatings on electronic equipment and components.

• Medical industry: The medical equipment industry often uses metal electroplating to improve the biocompatibility of components, especially implants. Gold, silver and titanium are commonly used in this industry for their biocompatibility, corrosion resistance, hardness and wear resistance, all of which are essential for implants and joint replacements.
• Aerospace industry: The aerospace industry frequently uses titanium for aircraft manufacturing due to its high strength-to-weight ratio. Nickel plating is also commonly used in this industry to protect against corrosion and wear, while copper is used to improve heat resistance.
• Oil and gas industry: Corrosion protection is a primary concern of the oil and gas industry due to the nature of petrochemicals. Electroless nickel plating is often used in this industry to help protect piping and other components from corrosion, which helps improve the longevity of parts.

Many other industries, including the firearms, military and defense industries, also use electroplating in various applications. All of these industries favor electroplating for its functional capabilities, as well as its low cost and flexibility of application.

ELECTROPLATING EXAMPLES

There are many specific examples of electroplating applications across various industries. Some of these are detailed below:

• • Copper plating of semiconductors: Various metal plating options are used in the electronics industry. Copper plating is commonly used to increase the ability of semiconductors and circuits to conduct electricity.

• Nickel plating of hard drives: Nickel is a magnetic metal, which is an essential property for hard drives. Hard drives require magnetism to improve disc reading, so hard drives are commonly electroplated with nickel during the manufacturing process.
• Palladium plating of catalytic converters: Palladium plating is commonly used in the automotive industry, specifically on catalytic converters. Palladium absorbs excess hydrogen during the manufacturing process, an element that negatively impacts the functionality of catalytic converters. Plating with palladium absorbs this excess hydrogen, improving catalytic converter performance.
• Electroless nickel plating of aerospace components: Black electroless nickel plating is capable of absorbing light and energy. This is an essential quality in the manufacturing of various types of defense vehicles. Many defense and aerospace industry manufacturers choose to use this plating option to ensure compliance with industry standards, including the Department of Defense guidelines.

With our extensive experience in a range of industries, SPC can assist with these electroplating applications and more, offering a range of cost-effective plating services.

CHOOSE SPC

Determining your best manufacturing options is essential for your company&#;s efficiency. Electroplating serves as a functionally and financially beneficial option for a variety of applications, but you need to partner with the right plating company to see all the benefits. There are several factors that influence the results of electroplating. Sharretts Plating Company can help.

SPC has over nine decades of experience in the industry, developing a wide range of cost-effective plating and metal finishing processes to suit the needs of companies across numerous industries. We can help you determine the best plating method for your project, as well as the type of metal you&#;ll want to use. With SPC, you can trust us to provide experienced, customer-focused service from start to finish.

Contact SPC to learn more about the electroplating process and how it could benefit your business and request a free quote now!

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