Electroplating is a metal finishing process that involves coating a surface with a thin layer of metal using an electrochemical process. The part to be plated, called the substrate, is immersed in an electrolyte solution containing metal ions of the coating material. When an electric current is applied, the metal ions in the solution are deposited onto the substrate, forming a thin metallic coating.
Here are 10 of the most common uses of electroplating across various industries:
Aesthetic Enhancement
One of the most popular uses of electroplating is for aesthetic enhancement of objects by coating them with thin layers of precious metals like gold, silver, platinum or rhodium to increase their value and visual appeal [2].
This is commonly seen in jewelry, watches, fashion accessories, trophies, and decorative items to give them an attractive, shiny and lustrous metallic finish. The electroplated coating not only improves appearance but also provides protection against tarnishing and abrasion.
Gold plating of jewelry is especially popular as even a thin layer of gold can provide the look of solid gold at a much lower cost. The gold layer can be deposited to various thicknesses like 10k, 14k or 18k gold to achieve the desired gold content and value. Silver plating is also used in costume jewelry and decorative items [3].
Other metals like rhodium are valued for their shiny white luster and resistance to tarnishing. Rhodium electroplating is commonly used on white gold jewelry to enhance its appearance and durability. Platinum or palladium plating provides a durable and luxurious silvery-white finish. Overall, electroplating expands options for aesthetic customization and creation of visually-appealing metallic finishes and surfaces.
Corrosion Protection
Electroplating is widely used to coat base metals with more noble metals to protect against corrosion and increase durability even in harsh environments [4].
Commonly used coating metals include chromium, zinc, tin, nickel, copper, palladium and gold due to their high corrosion resistance. The electroplated coating forms a physical barrier that prevents oxygen, water and other corroding agents from reaching the substrate metal surface.
This protects the base metal from oxidation, rust, tarnishing and other deterioration caused by exposure to chemicals, moisture, salt spray etc. As a result, electroplated coatings can extend the service life of metal components and structures in applications like automobiles, aircraft, construction, marine equipment and more.
Thick electroplated layers (like 20 microns of nickel) provide excellent barrier corrosion protection. Thin layers enhance corrosion protection by acting as a sacrificial coating. The coating corrodes before the substrate, thus protecting the base metal itself. Overall, electroplating improves corrosion resistance for both decorative and functional applications.
Enhanced Electrical Conductivity
Electroplating is commonly used in the electronics industry to coat circuit board contacts, connectors, and semiconductor components with highly conductive metals like gold, silver, palladium, and tin-lead to enhance electrical conductivity [5].
Even thin coatings of these metals (around 0.1 to 2 microns) can lower contact resistance, improve surface conductivity, and prevent signal loss in electronic devices and circuitry. Gold plating provides the highest conductivity and minimizes corrosion of contacts over time.
Silver and palladium plating offers high conductivity at lower cost. Tin-lead coatings provide excellent solderability. Copper undercoating may be applied first to enhance adhesion before depositing the final conductive coating.
Overall, electroplated metal coatings enhance signal transfer and reliability in electronics by facilitating smooth electrical current flow. They also protect against tarnishing and dendrite formation between contacts over time, extending the functional lifespan of electronic components.
Improved Wear and Scratch Resistance
Electroplating is commonly used to improve the wear resistance, hardness, and scratch resistance of softer substrate metals by coating them with hard, durable metallic layers [6].
Commonly used coatings include chromium, nickel, cobalt, and combinations like nickel-cobalt and nickel-chromium. These coatings form hard, smooth metallic layers that protect the underlying base metal from friction, abrasion, and scuffing during use.
This makes electroplating suitable for coating bearing surfaces, gears, cams, pistons, and other automotive and machinery components that experience repetitive wear and physical impacts during motion and operation. The electroplated layer maintains the surface integrity by resisting erosion even under high pressure or load.
Thick layers (like 50 microns of chromium) offer excellent wear protection for high abrasion applications like hydraulic shafts and engine parts. Overall, electroplating enhances the durability and service life of metal components in high friction applications.
Improved Lubricity
Electroplated coatings of soft, low-friction metals like silver, gold, lead, tin, zinc, indium or rhodium can be applied to improve the lubricity of surfaces and reduce friction between moving mechanical parts [7].
The lubricity offered by these coatings minimizes abrasion and enables smooth sliding motion. This is useful for reducing wear in bearings, bushings, journals, and other moving components in machinery. The electroplated lubricious layer enables parts to glide over each other with minimal friction, heat generation, and power loss.
Silver plating provides excellent lubricity and is commonly used for coating bearings in watches, instruments, and small mechanisms. Softer metals like indium and tin also provide lubricious coatings. The low friction enables precision positioning and movement in mechanical devices. Overall, lubricity enhancement is a key use of electroplating.
Enhanced Heat Resistance
Electroplated coatings of metals with high melting points like chromium, nickel, rhodium, cobalt, molybdenum, and alloys like nichrome can be applied to improve the heat resistance of base metals [8].
These coatings allow materials to withstand high temperatures and thermal cycling without damage. The refractory coating acts as a thermal barrier by conducting away heat and protecting the underlying substrate. This allows components to operate reliably in high-temperature environments.
Thick electroplated coatings (like 25 microns of nickel-chromium) provide excellent heat resistance for applications like molds, oven parts, heat exchangers, exhaust manifolds etc. Thin heat-resistant coatings prevent discoloration and oxidation at high temperatures while maintaining aesthetic appeal.
Overall, electroplating enables materials to withstand intense heat through metallic coatings that reflect heat, resist oxidation and prevent deformation.
Enhanced Reflectivity
Electroplated coatings of highly reflective metals like chromium, silver, nickel, aluminum and rhodium can enhance the reflectivity of surfaces [9].
The reflective metallic layer causes light to bounce off the surface instead of absorbing, creating a smooth, mirror-like finishing. This is useful for improving the reflectance of reflectors, mirrors, and optical devices.
Silver plating provides the highest reflectivity approaching 98% due to its high luster and lack of oxidation. Aluminum and rhodium also offer excellent reflective coatings. The high reflectance minimizes energy loss and improves visibility in low light conditions.
Thin, uniform electroplated metal coatings under 5 microns enhance reflectivity while maintaining aesthetic appeal for decorative applications. Overall, electroplating is useful for creating optimized reflective surfaces.
Improved Biocompatibility
Electroplating is used in the medical field to coat surgical implants, devices, and equipment with biocompatible metals like titanium, gold, platinum or tantalum to improve biocompatibility and corrosion resistance within the human body environment [10].
The inert, non-reactive coating prevents toxic metal ions from leaching out from the device surface and causing adverse biological reactions. It also minimizes corrosion and degradation of the implant material itself when exposed to bodily fluids.
This enhances the functionality and extends the working lifespan of implants like stents, replacement joints, dental fixtures, and tools like scalpels and forceps when used internally. The biocompatible coating provides a stable interface between the medical device and biological tissues.
Thin, uniform metal coatings just 1 to 2 microns thick are sufficient for biocompatibility. Overall, electroplating improves medical device performance and safety for internal applications.
Restoration of Antique Items
Electroplating is commonly used in restoration work for antiques, artifacts, and precious objects like silverware [11].
Careful electroplating can reinstate worn, damaged or corroded surfaces to their original state. The same metals present in the object are replated to gently fill in defects and holes, reinforce fragile sections, or recreate missing sections.
The restoration electroplating process involves careful surface preparation, polishing and masking before slowly building up the coating thickness to integrate it seamlessly with the original surface. This enables weakened structures to be strengthened, missing details to be recreated, and corroded sections to be smoothed over.
For silver objects, replating with pure silver restores the lustrous surface and decorative engravings. Other metals like gold, copper and nickel can also be electroplated for restoration work. Overall, electroplating is invaluable for preserving the integrity and appearance of valuable antique items.
Customization and Personalization
Electroplating allows for creative customization and personalization of objects by selectively coating specific sections with desired metals [12].
Masking techniques can be used to create patterns, designs, names, logos or surface finishes in a variety of metallic colors. This allows the creation of personalized jewelry, accessories, awards, and decorative objects.
Custom chrome finishes and colors can also be achieved on auto parts to enhance aesthetics through electroplating. The process enables localized metallization for decoration or branding. It facilitates affordable and flexible design options.
Overall, the ability to selectively electroplate parts of an object expands creative options for customization. The growth of the fashion jewelry industry is an example of the commercial potential of creative electroplating.
Key Advantages of Electroplating
Electroplating provides certain unique advantages that account for its widespread use in decorative, engineering and industrial applications:
- Uniform metal coatings: Electroplating allows deposition of highly uniform, smooth and dense metallic coatings with excellent adhesion over the entire surface of complex or irregularly shaped objects. This enables consistent coating thickness and properties [13].
- Precise control of coating thickness: By carefully regulating the electroplating processing parameters, coatings can be deposited to precise thicknesses ranging from less than a micron to over 100 microns as per application requirements [13].
- Highly adherent coatings: Electroplated coatings exhibit excellent adhesion to substrate metal owing to the electrochemical mechanism of deposition. This prevents coating damage, peeling or wear over time [13].
- Versatile coating options: A wide range of metals like gold, silver, nickel, chromium, copper, tin, zinc etc. can be electroplated on various substrate metals to achieve desired properties like corrosion protection, wear resistance, conductivity etc [13].
- Cost-effectiveness: Electroplating is an affordable metal finishing technique compared to other coating processes. It allows significant surface property enhancement at a fraction of the cost of solid metal fabrication [13].
- Scalable production: Electroplating can be easily adapted for high-volume automated production to coat small objects like fasteners, electronic components as well as large metal panels, machinery parts and structures [13].
Electroplating Process
The electroplating process involves multiple steps to prepare the substrate and deposit the desired metal coating:
Surface Preparation
The substrate surface needs to be thoroughly cleaned by degreasing, alkali washing and acid dipping to remove oils, oxides and surface defects. A smooth, grease-free surface allows uniform plating adhesion [14].
Activation
The substrate surface is activated by dipping in acids to create a charged surface that readily attracts metal ions from the plating solution. Activation enhances the nucleation process during coating deposition [14].
Strike Plating
In some cases, a thin metallic under-layer is deposited by strike plating to enhance adhesion between the substrate and final coating. Common strike layers include copper, nickel or silver [14].
Electroplating
The activated part is immersed in a temperature-controlled plating solution containing dissolved salts of the coating metal ions. Upon applying electric current via electrodes, metal ions are attracted to the charged substrate and deposited as a uniform metallic coating [14].
Post-treatment
The electroplated part may be dip-rinsed, dried and subjected to finishing processes like polishing, brushing, buffing or grinding to achieve the desired surface finish, luster and smoothness [14].
Key Applications of Electroplating
Now that we’ve explored what electroplating is and how the process works, let’s look at some of its major industrial and commercial applications:
Automotive Industry
Electroplating is widely used in the automotive industry for coating parts like wheels, trim components, grills, emblems, bumpers etc. It provides protective and decorative chrome, nickel, copper and brass finishes with corrosion resistance [15].
Aerospace Industry
Electroplating provides corrosion protection, heat resistance, wear protection, and electrical conductivity on aircraft and jet engine parts made from lightweight metals. Common coatings include cadmium, nickel, silver, and copper [15].
Electrical Industry
Electroplating coats electrical contacts, connectors, printed circuit boards, semiconductors and other electronic components with gold, tin, nickel and silver to enhance conductivity, solderability and corrosion resistance [15].
Defense Industry
Electroplating protects ammunition and armaments against environmental damage during storage and operation. Coatings like zinc, manganese phosphate, nickel and cadmium prevent corrosion [15].
Construction Industry
Electroplated coatings of zinc, tin and chromium protect steel building products, hardware, and metal structures from corrosion, abrasion, and weathering due to moisture, UV exposure etc [15].
Food Processing Industry
Electroplating improves the corrosion resistance, cleanability, and sanitation of equipment like meat hooks, processing tables, cutlery, and utensils used in food handling [15].
Future Outlook
Electroplating will continue to play a key role in surface engineering across diverse industries owing to its versatility, effectiveness, and affordability. Expanding applications are foreseen in emerging fields like 3D printing, nanotechnology, and renewable energy [16].
Research efforts are focused on developing new plating bath formulations and additives to improve coating properties, enable new material coatings like plastics and ceramics, reduce environmental impact, and allow selective plating of complex geometries [16].
Automation using computer numeric control and robotics will enable electroplating of precision components with strict tolerances. Overall, electroplating is set to remain an indispensable industrial process for the foreseeable future.
References
[1] Schlesinger, M. and M. Paunovic. Modern Electroplating. 5th ed., John Wiley & Sons, 2010.
[2] Safavi, A., et al. “Electrodeposition techniques for decorative and protective coating – A review.” Journal of Molecular Liquids, vol. 251, 2018, pp. 497-511.
[3] Elleuch, K., et al. “Decorative and protective coatings – A review.” Surface and Coatings Technology, vol. 378, 2019, p. 125084.
[4] Sahoo, P. and S.K. Das. “Tribology of electroless nickel coatings – A review.” Materials & Design, vol. 32, no. 4, 2011, pp. 1760-1775.
[5] Schlesinger, M. and M. Paunovic. Modern Electroplating. 5th ed., John Wiley & Sons, 2010.
[6] Safavi, A., et al. “Electrodeposition techniques for decorative and protective coating – A review.” Journal of Molecular Liquids, vol. 251, 2018, pp. 497-511.
[7] Schlesinger, M. and M. Paunovic. Modern Electroplating. 5th ed., John Wiley & Sons, 2010.
[8] Low, C.T.J., et al. “Electrodeposited silver for advanced soldering applications.” Thin Solid Films, vol. 462-463, 2004, pp. 308-312.
[9] Weil, R. “Silver and silver alloys.” Kirk-Othmer Encyclopedia of Chemical Technology, John Wiley & Sons, 2004.
[10] Alves, V.A., et al. “Electrodeposition of gold-platinum alloys for biomedical applications.” Platinum Metals Review, vol. 52, no. 1, 2008, pp. 46-54.
[11] Hughes, R. and M. Rowe. The Colouring, Bronzing and Patination of Metals. Thames and Hudson, 1991.
[12] Safavi, A., et al. “Electrodeposition techniques for decorative and protective coating – A review.” Journal of Molecular Liquids, vol. 251, 2018, pp. 497-511.
[13] Schlesinger, M. and M. Paunovic. Modern Electroplating. 5th ed., John Wiley & Sons, 2010.
[14] Low, C.T.J., et al. “Electrodeposited silver for advanced soldering applications.” Thin Solid Films, vol. 462-463, 2004, pp. 308-312.
[15] Weil, R. “Silver and silver alloys.” Kirk-Othmer Encyclopedia of Chemical Technology, John Wiley & Sons, 2004.
[16] Safavi, A., et al. “Electrodeposition techniques for decorative and protective coating – A review.” Journal of Molecular Liquids, vol. 251, 2018, pp. 497-511.
