Electroplating: Process, Types and Applications
- Gavin Leo
In the industrial setting, it is common to subject materials to coating. Manufacturers do this to not only enhance the aesthetic appeal but also to add protection against extreme conditions and damage. Metals, concrete, and plastics can all undergo coating, but is the former that appears to be most common.
In this article, we will review one coating method – electroplating. Many manufacturers use this plating method for their surface treatment projects. Electroplating has many benefits that manufacturers find valuable. For instance, they can design a product with steel or zinc, and then apply a more expensive coating for protection or enhanced visual appeal.
Read on as we explore the electroplating process basics, factors for great metal surface finishing results, the limitations of the process, the applications of the surface finish, and much more.
What is Electroplating?
Electroplating is a coating technique based on the hydrolysis concept. Industries use the technique to plate a substrate with a thin layer of metal. Typically, the goal of electroplating is to decorate the substrate or protect it against elements. It involves coating a substrate or base metal with a more noble or superior metal using hydrolysis.
A good example is when one coats iron with chromium to promote corrosion resistance and enhance visual appeal. Machinery parts often have chromium coatings on them for these reasons.
Electrochemical deposition emerged in 1805 thanks to the efforts of Luigi V. Brugnatelli. He had a setup comprising of a battery, a gold solution, and a wire. He managed to transfer the shiny look of gold onto the metal.
A few decades later in the 1840s, the Italian’s works became extremely popular in Russia and Britain. Many other businesses emerged afterwards and patents exchanged hands. To date, electroplating is widely used across the world.
Electroplating Process
So, how does electroplating work? The setup of the electroplating process involves two electrodes – the cathode and the anode. These are the negative electrode and positive electrode respectively. An electric current and electrolyte solution complete the setup, as shown in the example involving copper sulfate below.
Each of these plays an instrumental role in making electroplating effective. Let’s analyze these 4 primary components in detail:
#1 Anode
A primary component in the electroplating circuit is the positive electrode, also called the anode. It is the metal that will cover the substrate once the process is complete.
#2 Cathode
This is the metal that is being electroplated. It is the negative electrode in this setup. Its other name is substrate.
#3 Solution
There’s also the electrolyte solution, where the electrodepositing process happens. The role of the aqueous solution in the electrolytic cell is to facilitate the electricity flow. The electrolyte solution typically contains metal salts, often in copper sulfate solution form. The metal salt component provides the metal ions required in the process.
#4 Power Source
The power source supplies the electric current to the electroplating circuit. This current gets into the plating solution via the positive electrode.
For a better understanding of electroplating, consider the gold coating scenario. In this case, the aim is to deposit a layer of gold onto a piece of jewelry. As expected, the metal jewelry or any other substrate will be at the negative electrode and the gold at the anode. The two electrodes remain immersed in the electrolyte. Next, the DC power supply is subjected to the anode, and oxidization starts.
With the current, the process can reduce dissolved metal cations and form a layer on the negative electrode. Gold metal ions are reduced to metal atoms during the chemical reaction. Gold atoms oxidize and dissolve into the electrolyte as they are deposited on the electrode in the form of a thin layer.
Electroplating vs Electroless Plating Process
Many people tend to confuse between electroplating and electroless plating processes. There is a difference between the two processes regarding the use of electric current. The electroplating process uses an electric current to enable the binding of metal particles.
Electroless plating does not use an electric current. It is based purely on the chemical composition of the components. Since plating metal this way does not require electric current, electroless plating works even for materials that have no electrical conductivity.
Types of Electroplating Methods
You can achieve electroplating through several approaches or methods. The most prominent ones are mass or barrel plating, line plating, rack plating, and continuous plating. Each of these methods has a different procedure and other elements, as captured in the table below.
Electroplating Material Options
Electroplating works for a wide range of metals and materials, but some are more commonly used than others. The most popular metals for plating solutions are:
Zinc plating
Gold Plating
Palladium plating
Silver plating
Nickel plating
Copper plating
Chrome plating
Factors Affecting The Electroplating Finishes
Electrochemical deposition is diverse and has many applications, but it may not always go according to plan. Several factors can determine how well plating occurs. Here are a few of them:
Bath Conditions
Bath conditions refer to the concentration in the bath. Bath concentration determines the quality of the finish. Under normal circumstances, a concentration increase in the bath leads to a concentration increase in the metal ions in the coating solution.
In other words, an increase in bath concentration promotes the deposition rate during the electroplating process.
Temperature
The temperature can affect the electroplating finish too. When the temperature is too low, small metallic crystals are likely to form. Higher bath temperature leads to the formation of larger crystals. Here’s why a high bath temperature is preferable:
Increased salt solubility in the electrolyte solution
Increased metal concentration and current densities
Improved electrical conductivity of the components for stronger bonds
Decreased hydrogen occlusion
Substrate Surface Finish
The substrate surface finish is an equally important factor to consider for the electroplating finish. Being an electrochemical process, electroplating is sensitive to the substrate surface condition.
Substrate surface preparation before electro-deposition is, therefore, necessary for the best surface finish results. Engineers use several approaches including belt polishing, metal surface blasting, buffing, and barrel tumbling. Other ways of preparing the substrate surface are spin texturing, diamond cutting, and polishing through the vibratory barrel method.
Plating Time
The effect of plating time on the electroplating finish is derived from Faraday’s Law of Electrolysis. According to the law;
Q=I × T
- Where Q is the quantity of charge flow,
- I is the current flow, and T is the flow time
Based on this relationship, the plating thickness is directly proportional to the plating time.
Current Distribution
The level of uniformity of the coating depends on the current distribution. There is a phenomenon whereby metal ions favor particular sites on the cathode during the production process.
That’s why you are likely to witness discontinuities on the positive electrode. Thus, current density and distribution parameters in electroplating can determine how uniform the surface finish becomes.
The Benefits of Electroplating
Electroplating is widely used because it offers a range of benefits. From making the component more attractive to enhancing durability, there is so much to expect from the process. Here is a brief coverage of the benefits of electroplating:
Substrate Material Protection
In the manufacturing industry and the context of this article, the substrate material is the material on which the coating is applied. Once the material has been electroplated, it hardens and lasts longer. With the extra metal layer, you can expect your substrate materials to perform better under rough conditions thanks to increased wear resistance.
Reduced Friction
Components such as electrical connectors can generate heat and wear out under friction. To reduce friction and thus manage this issue, manufacturers can apply a plated layer. Nickel electroplating is particularly popular for this application.
Improving Conductivity of Parts
If you have an electrical project, you can greatly enhance its electrical conductivity using superior surface finishing services. We highly recommend copper for electroplating because of its high electrical conductivity. These materials are also cost-effective so your project costs can be under control.
Improved Adhesion
If you are planning to add an outer coating such as paint on the metal, you want a surface treatment solution that promotes adhesion. That’s exactly what electroplating offers. Copper plating is particularly renowned for its adhesion qualities. With better adhesion, the surface becomes uniform with a high-quality appearance.
Enhanced Appearance
Specific benefits of the electroplating method may vary from industry to industry, but one of the primary benefits of the process is the resulting visual appeal. Electro-deposition through gold plating and others result in a smooth, even, and bright metal object. The improved surface qualities can make the product or component visually appealing.
The Limitations of Electroplating
Electroplating is an intricate process that involves the molecular behavior of metals. Therefore and like any other engineering process, it has its limitations as discussed next:
Substrate Material Compatibility
Incompatibility of materials is a serious limitation in electroplating. Note that the solid substrate can be any material. However, there are ways of bypassing the incompatibility challenge. Engineers have electroplated fabric and other organic materials.
As long as the conductivity condition is met, electroplating can take place. The substrate can be made conductive first. This can be achieved through coating with a conductive layer.
Uniformity Challenges
Electroplated surfaces are notorious for being uneven. The shape of the substrate may affect the amount of deposition achieved. Some areas will have more coating than others due to the relationship between distance, resistance, and current.
The design engineer, aware of this surface uniformity fact, should build the product with the coating thickness at every place of the component/product in mind.
High Costs
Three categories of costs matter in the electroplating process: Labor costs, equipment costs, and base material costs. These factors can make the costs among the different electroplating methods vary. Generally, electroplating can be lengthy and uneconomical, particularly for small parts.
Environmental
Electroplating shops can produce cyanide, heavy metals, and other toxic air pollutants. Volatile organic compounds (VOC) may also emanate from degreasing solutions used in the facilities.
Non-compliant shops may also produce hexavalent chromium and other heavy metals. These pollutants can have adverse effects on the environment and human health. For instance, experts link cyanide with heart and nervous system issues.
Applications of Electroplating
Whether your business is looking to improve the durability of products or enhance protection against corrosion, our electroplating services come in handy. Electroplating is widely used in different industries. Here, we discuss a few of those electroplating applications concerning the most popular industries.
Aerospace
The strength-to-weight ratio is a critical parameter for materials in the aerospace industry. Titanium is a common material in the industry due to its high strength-to-weight ratio. Nickel is also commonly used in this industry.
Nickel electroplating helps make other materials highly resistant to wear and corrosion. Copper electroplating is also popular because the material has high heat resistance.
Automotive
The automotive industry products are prone to harsh conditions. Due to this, automotive makers employ electroplating to enhance the effectiveness of their products.
Electroplating is particularly crucial in enhancing corrosion-resistant qualities. To counter the rust problem, manufacturers may apply the zinc-nickel plating. Other types of electroplating solutions are also applicable to handle unique material challenges in the industry.
Medical and Dental
The medical and dental industry has been using electroplating techniques for decades. A common area is in implants. Regular electroplating materials in this industry are titanium and gold.
Medics cite the wear resistance, corrosion resistance, and biocompatibility of these materials as the standout benefits. Joints and dental implants based on these materials are dependable.
Prototyping
Engineers use electroplating to build prototypes for their electroplating products. They want to be sure that the substrate and coating material will perform as expected. Through low-cost prototyping, they discover design errors and increase the longevity of the plating material.
Why Choose Electroplating Services in Aria Manufacturing Limited
Choosing the right partner for electroplating services can remove any uncertainty from your surface treatment projects. Such a partner has the right team to help you realize all the benefits of electroplating.
Aria Manufacturing Limited is the provider you are looking for. We boast of many years of experience, offering diverse metal electroplating solutions for countless applications in different industries. With us, you can be sure of getting the ideal recommendation for a plating method. We take careful consideration of the different metals available, among other factors.
Our services are customer-centric coupled with quality and affordability. Contact our team and ask for an instant quote today and more on electroplating.