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

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

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.

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.

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.

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Hazardous nature

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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.

Electroplating lets you combine the strength, electrical conductivity, abrasion and corrosion resistance, and appearance of certain metals with different materials that boast their own benefits, such as affordable and/or lightweight metals or plastics.

In this guide, you&#;ll learn why many engineers, researchers, and artists use electroplating and metal plating in every stage of manufacturing&#;from prototyping to mass production.

White Paper

Strength from Metal: Strategies and Use Cases for Electroplating SLA Parts

Read on to learn how engineers are adding metal to resin 3D prints, and why hybrid metal parts can open doors to a surprising range of applications, including (but not limited to) end-use strength and durability.

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What Is Electroplating?

Electroplating is the process of using electrodeposition to coat an object in a layer of metal(s). Engineers use controlled electrolysis to transfer the desired metal coating from an anode (a part containing the metal that will be used as the plating) to a cathode (the part to be plated).

The anode and cathode are placed in an electrolyte chemical bath and exposed to a continuous electrical charge. Electricity causes negatively charged ions (anions) to move to the anode and positively charged ions (cations) to transfer to the cathode, covering or plating the desired part in an even metal coating. Electroplating takes a substrate material (often a lighter and/or lower-cost material) and encapsulates the substrate in a thin shell of metal, such as nickel or copper.

Electroplating is most commonly applied to other metals, because of the basic requirement that the underlying material (the substrate) is conductive. Although less common, autocatalytic pre-coatings have been developed which produce an ultra-thin conductive interface, allowing a variety of metals - most notably copper and nickel alloys - to be plated onto plastic parts. 

Electroplating vs. Electroforming

Electroplating and electroforming are both performed using electrodeposition. The difference is that electroforming uses a mold that is removed after a part is formed. Electroforming is used to create solid metal pieces, whereas electroplating is used to cover an existing part (which is made of a different material) in metal.

Electroplating Material Options

You can electroplate a single metal onto an object, or a combination of metals. Many manufacturers choose to layer metals, such as copper and nickel, to maximize strength and conductivity. Materials commonly used in electroplating include:

• Brass
• Cadmium
• Chromium
• Copper
• Gold
• Iron
• Nickel
• Silver
• Titanium
• Zinc

Substrates can be made of almost any material, from stainless steel and other metals to plastics. Artisans have electroplated organic materials, such as flowers, as well as soft fabric ribbons. 

It&#;s important to note that non-conductive substrates such as plastic, wood, or glass must first be made conductive before they can be electroplated. This can be done by coating a non-conductive substrate in a layer of conductive paint or spray.

Electroplating (3D Printed) Plastic Parts

Thanks to scientific advances in materials and plastic manufacturing, lightweight and low cost plastic parts have replaced more expensive metal parts in a wide variety of applications serving various industries, from automobiles to plumbing pipes.

Although plastic boasts an array of advantages over metal, there are many applications where metal still reigns supreme. Try as you might, you&#;ll never get plastic to have the same opulent finish as copper. And while plastic might be more flexible material than the majority of metals, it&#;s not nearly as strong. This is where metal plating comes in.

3D printing offers unique advantages when combined with electroplating. Engineers often choose to 3D print substrates because of additive manufacturing&#;s design freedom. It is often cheaper to electroplate 3D printed parts than to cast, machine, or use other manufacturing methods, especially when it comes to prototyping.

Stereolithography (SLA) 3D printing is ideal for electroplating because it creates 3D printed parts with very smooth or finely textured surfaces that make the transition between the two materials&#;plastics and metals&#;seamless. It also creates watertight parts that won&#;t get damaged when submerged in the chemical bath required during the electroplating process.

From an engineering standpoint, the combination of 3D printing and electroplating offers unique tensile strength options for finished designs. As you can see in the chart above, the combination of these two manufacturing processes bridges the gap in tensile strength between the two material groups.

Metal plating can have a major impact on the mechanical performance of (3D printed) plastic parts. With a structural metal skin and a lightweight plastic core, parts can be produced with surprisingly high flexural strength characteristics.

In addition to improving mechanical behavior, electroplating can be used to protect plastic parts from environmental degradation. In applications where plastic parts are exposed to chemical attack or ultraviolet light, metal plating provides a permanent barrier that can extend the life of your parts from months to years.

When used as an aesthetic treatment, plating offers an easy way to create prototypes that both look and feel like metal. Depending on the plate thickness, electroplated plastic can be thin and light, or add noticeable weight to a part. Thicker electroplated coatings can even be texturized or polished to achieve a variety of metal finishes, from cast aluminum to mirrored chrome. More complex textures can be achieved by 3D printing a textured resin substrate.

Given the potential combinations of 3D printable materials, a variety of plating metals, and plate thickness ratios, it&#;s easy to see how electroplating gives engineers a new field of design options to consider.

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The Benefits of Electroplating

Electroplating offers many benefits, including increased strength, lifespan, and conductivity of parts. Engineers, manufacturers, and artists capitalize on these benefits in a variety of ways.

Engineers often use electroplating to increase the strength and durability of various designs. You can increase the tensile strength of various parts by coating them in metals such as copper and nickel. Place a metallic skin on parts and you can improve their resistance to environmental factors like chemical exposure and UV light for outdoor or corrosive applications.

Artists often use electroplating to preserve natural elements prone to decay, such as leaves, and turn them into more durable works of art. In the medical community, electroplating is used to make medical implants that are corrosion-resistant and can be properly sterilized.

Electroplating is an effective way to add cosmetic metal finishes to customer products, sculptures, figurines, and art pieces. Many manufacturers also choose to electroplate a substrate to create more lightweight parts that are easier and cheaper to move and ship.

Electroplating also offers the benefit of conductivity. Because metals are inherently conductive, electroplating is a great way to increase the conductivity of a part. Antennas, electrical components, and other parts can be electroplated to increase performance.

The Limitations of Electroplating

Though electroplating boasts plenty of benefits, its limitations lie in the complexity and hazardous nature of the process itself. Workers performing electroplating can suffer from hexavalent chromium exposure if they don&#;t take proper precautions. It is essential for workers to have a properly ventilated workspace. The U.S. Department of Labor Occupational Safety and Health Administration has published numerous documents outlining the risks involved in electroplating.

Although it is possible to electroplate resin parts yourself, amateur users may run into difficulty. The main reason is quality and capability. Laminate adhesion strength using DIY electroplating methods is usually lower than what is achieved by a professional plating service. Structural plating, which requires long plate times, multiple baths, and compatibility between metals, is quite difficult to execute reliably. Successful applications of in-house plating are typically simple and small, such as jewelry prototyping, and thin (single layer) RF copper coatings.

Because of the expertise required and the dangers involved, many engineers and designers choose to hire a third-party electroplating manufacturer specializing in this process. Luckily, several companies, such as RePliForm and Sharretts Plating, specialize in custom electroplating projects. Download our white paper for a list of electroplating services by region and job size.

The video above shows how to electroplate with easy-to-acquire tools, such as a cell charger and spare copper pipe. We recommend you wear a mask, gloves, and eye protection while electroplating and only work in a well-ventilated space.

The Many Applications of Electroplating

Numerous industries use electroplating to make everything from engagement rings to electrical antennas. Here are some common examples:

Aerospace

Many airplane components are electroplated to add a &#;sacrificial coating,&#; which increases the lifespan of parts by slowing down corrosion. Because aircraft components are subject to extreme temperature changes and environmental factors, an additional metal layer is added to a metal substrate so that the functionality of a part isn&#;t compromised by normal wear and tear.

Many steel bolts and fasteners designed for the aerospace industry are electroplated in chromium (or, more recently, zinc-nickel, due to changing restrictions).

Art and Home Decor

Type the word &#;electroplated&#; into Etsy, and you&#;ll be presented with a vast array of electroplated home decor and one-of-a-kind keepsakes. Artisans often turn biodegradable items, including flowers, branches, and even bugs, into durable and long-lasting pieces of art with this process. You can employ electroplating to show off and preserve fine details in items that would otherwise quickly decompose.

Electroplating is often used to create art, such as this copper-plated beetle and honeycomb. (image source)

Digital designers sometimes use electroplating to produce sculptures. Designers can 3D print a substrate using a desktop 3D printer and then electroplate the design in copper, silver, gold, or any metal of choice to achieve their desired finish. Combining 3D printing with electroplating in this manner produces pieces that are easier (and cheaper) to manufacture, while still having the same look and finish as a sculpture that is solid cast metal.

Automotive

Electroplating is very common in the automotive industry. Many major automotive companies use electroplating to create chrome bumpers and other metal parts.

Electroplating can also be used to create custom parts for concept vehicles as well. For example, VW teamed up with Autodesk to create hubcaps for their &#;Type 20&#; concept vehicle. The prototype hubcaps were 3D-printed and then electroplated. 

Restoration companies and vehicle customization businesses also use electroplating to apply nickel, chrome, and other finishes to various car and motorcycle parts.

Jewelry

Electroplating is perhaps most commonly associated with the jewelry industry and precious metals. Jewelry designers and manufacturers rely on this process to enhance the color, durability, and aesthetic appeal of rings, bracelets, pendants, and a wide range of other items.

When you see jewelry that is described as being &#;gold plated&#; or &#;silver plated,&#; there&#;s a high chance the piece you&#;re looking at was electroplated. Combinations of various metals are used to achieve uniquely hued finishes. For example, gold is often combined with copper and silver to create rose gold.

Medical and Dental

Power

Prototyping

Producing custom or low-volume metal parts for prototyping can be very costly and time-consuming with traditional manufacturing processes. As a result, engineers often combine electroplating with 3D printing for a low-cost and time-saving solution.

For example, Andreas Osterwalder of the Swiss Federal Institute of Technology in Lausanne (EPFL) has been able to speed up the prototyping process and reduce costs of advanced experimental setups by 3D printing new designs himself on his Formlabs resin 3D printer and working with Galvotec to have those parts electroplated.

RF and Microwave Products

Antennas need to have electrical conductivity to propagate radio waves. While plastic 3D printed parts don&#;t conduct electricity, they offer almost infinite design freedom and materials with good mechanical and thermal properties. These benefits can be combined with electroplating to achieve the desired conductivity, resulting in a great solution for custom antennas for research and development in the automotive, defense, medicine, and education.

Best Practices for Electroplating 3D Printed Parts

Electroplated composites are a means to a wide variety of ends. Because of its versatility, electroplating opens up countless possibilities across different industries. Want to learn more about electroplating 3D printed parts?

Download our white paper to learn how engineers are adding metal to resin 3D prints, and why hybrid metal parts can open doors to a surprising range of applications, including (but not limited to) enduse strength and durability. By the end of the white paper, you will learn new ways to apply electroplating, as well as design considerations and practical tips on using metal electroplating to amplify the performance of your SLA parts.

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