This article will take an in-depth look at types of metal plating.
The article will bring more detail on topics such as:
This chapter provides an overview of metal plating, detailing its definition, the various techniques involved, and the materials used in these processes.
Metal plating is the process of applying a metallic layer over the surface or substrate of a metal object or component. This can involve techniques like electroplating, where metal ions are deposited onto the surface using an electric current.
Electroless plating, in contrast, involves depositing metal ions onto a substrate without the use of electrodes. Such methods are designed to boost the material's resistance to corrosion, each having its unique advantages.
Besides offering protection against environmental damage, metal plating can also enhance a part's aesthetic appeal. Coatings are generally classified as industrial or commercial.
Commercial decorative coatings are intended for everyday objects to improve their look and durability. Typical applications include tools, silverware, and jewelry. Meanwhile, industrial coatings fortify metal parts, improving their durability to withstand harsh environments and enhancing the strength and protection of machine and vehicle components.
These coatings augment the metal's solderability, increase strength, and reduce friction, thereby lowering wear. These processes can also influence metal conductivity, potentially altering its electrical current capacity. Additionally, applying a metal coating can make surfaces suitable for painting and improve magnetic properties.
Several processes are involved in metal plating, including:
The electroplating process entails the use of electrodeposition to apply a metallic coating on the workpiece. This is managed through electrolysis, transferring the metal layer from the anode (which holds the metal for plating) to the cathode (the item to be plated), both immersed in an electrolyte solution with an ongoing electric current facilitating the process.
In this process, the electric current propels negatively charged ions toward the anode and positively charged ions toward the cathode, resulting in a consistent metal layer on the object. By the end of the procedure, the workpiece is enveloped in a thin metallic layer, often of copper or nickel.
Predominantly used for metals due to the requirement for conductivity, electroplating can also be adapted for certain plastics using special autocatalytic pre-coating methods that apply a thin conductive layer, enabling the plating of metals like nickel and copper onto these substrates.
Electroplating and electroforming both use electrodeposition, but they differ in that electroforming requires a mold, which is removed afterwards to reveal the formed part.
While electroforming is intended to create standalone metal pieces, electroplating serves to coat a pre-existing workpiece of a different material.
Various metals, either alone or combined, are electroplated onto items. Manufacturers often use layers of metals like nickel and copper to enhance strength and conductivity. Common materials used in electroplating include:
A broad range of materials can be used as substrates, from stainless steel and other metals to plastics. Even organic items, such as soft ribbons or flowers, can undergo electroplating. Non-conductive materials like plastic, glass, and wood must be prepped with a conductive coating before electroplating, typically by applying a conductive spray or paint.
Electroless plating is a chemical method of applying metallic coatings without electric current. It involves immersing the object in a solution with a reducing agent and catalyst to convert metal ions into a metal deposit on the surface. This technique frequently applies to plastics, such as those used in printed electronics, providing both cosmetic and durability benefits.
Diverging from electroplating’s reliance on electric currents, electroless plating creates chemical reactions in the solution, provisioning metal deposition without electricity. The reducing agent, often sodium hypophosphite, releases hydrogen to oxidize and yield a negative charge on the item, allowing for uniform metal deposition, even in complex shape scenarios.
This method is pivotal in making non-conductive surfaces, like plastics, ready for subsequent electroplating or any applications needing electrical conductivity.
Electroless nickel plating is prevalent, though copper, gold, and silver can similarly be applied. Known as electroless plating, auto-catalytic plating or chemical plating operates without an external electrical power source.
The process relies on a reducing agent like sodium hypophosphite to emit hydrogen, which becomes oxidized and produces a negative charge on the workpiece. Electroless plating ensures comprehensive metal ion deposition on parts, even along edges and in cavities, which is often arduous using electroplating.
This approach also facilitates layering conductive metal over non-conductive objects, setting them up for future electroplating tasks.
Immersion plating involves dipping a base metal into a solution with ions of more noble metals, triggering a replacement reaction that deposits a metallic coating on the base metal. Here, a metal with lower oxidation displaces ions with higher oxidation from the solution.
Used to improve electrical properties and coat adhesion, immersion plating or dip plating operates without external current. When a lesser noble metal, like copper, is immersed in a solution with more noble metal ions, it dissolves, releasing electrons and allowing noble metals to coat the substrate. The deposition halts when fully covered. Gold immersion occurs between 80°C and 90°C, while silver between 50°C and 60°C.
Both plating styles bolster a component's strength and corrosion resistance while enhancing its appearance. They differ primarily in electric current usage: electroplating uses current, electroless plating doesn’t.
In electroplating, a rectifier or battery provides current to a submerged component, transforming chemical states and creating a sturdy layer. This complex method requires meticulous cleanliness and possibly hazardous equipment for multi-layer applications.
Conversely, electroless plating is simpler, involving removing contaminants with chemicals before immersing the piece in an anti-oxidation solution. It produces components with excellent resistance to corrosion and friction.
Electroless nickel plating omits complex systems and equipment and doesn't risk electric hazards due to its electricity-free approach.
This chapter explores the various metal plating techniques according to the specific metals employed, detailing their unique properties, applications, benefits, and limitations. Understanding the range of plating metals and processes is crucial for industries ranging from electronics manufacturing and automotive engineering to aerospace, jewelry, and consumer goods, ensuring optimal performance and longevity of plated products.
Electroless nickel plating is an advanced metal finishing technique used to apply a uniform nickel-phosphorus alloy coating onto metal or plastic substrates. This method enhances surface hardness, corrosion resistance, and wear properties. Unlike traditional electroplating, electroless nickel plating operates through an autocatalytic chemical deposition, eliminating the need for an external electrical current and thereby ensuring highly uniform coverage, even on complex geometries and internal surfaces.
The electroless nickel plating process incorporates several essential surface preparation and plating stages, including:
Electroless nickel coatings can be deposited at rates ranging from 5 microns per hour to 25 microns per hour. This process supports virtually unlimited coating thickness but, as thickness increases, minor surface flaws or imperfections may become amplified. Applications generally use one of five distinct coating grades, tailored for wear resistance, corrosion prevention, or for use as a solderable or bonding underlayer in electronics and precision engineering.
Electroless nickel plating is often specified for products requiring enhanced wear and corrosion protection, uniform coating on intricate parts, reliable electrical conductivity, and improved solderability—making it an industry standard for printed circuit boards (PCBs), connectors, hydraulics, and valves.
Zinc plating—also referred to as galvanization—is a cost-effective corrosion protection process that applies a zinc layer to steel and iron parts. This sacrificial zinc coating prevents oxidation and rusting, improving part lifespan in challenging environments. It is widely used in automotive, construction, HVAC, and fastener production due to its effective barrier properties and affordability.
Key zinc plating methods include:
Modern variations sometimes add small amounts of aluminum or nickel to the zinc bath to achieve specific coating characteristics, such as enhanced fluidity for complex shapes or improved corrosion resistance in marine and industrial atmospheres.
Cadmium plating offers exceptional sacrificial corrosion protection and natural lubricity. Due to these properties, it has historically been favored for aerospace, military, and marine hardware exposed to high-risk corrosion and frequent disassembly cycles. Its ability to perform effectively in saltwater environments makes it suitable for bolts, fasteners, and landing gear components.
Environmental and health regulations have decreased the prevalence of cadmium plating, with many aerospace OEMs transitioning to zinc-nickel alloy plating and similar substitutes to meet evolving industry requirements for toxic-free protective coatings.
Chrome plating, also known as chromium electroplating, is used for both decorative and industrial applications. It delivers a lustrous, mirror-like finish combined with significant hardness, wear resistance, and exceptional corrosion protection. Automotive, motorcycle, and furniture parts often receive decorative chrome plating to enhance aesthetics and prevent oxidation, while heavy chrome deposits are used in industrial applications such as hydraulic cylinders, piston rods, and tooling where metal performance and longevity are critical.
The process uses chromic acid baths, available in both hexavalent and trivalent chromium systems. Trivalent chromium plating has become more popular as an environmentally safer alternative with reduced toxicity and easier waste treatment.
Aluminum metal offers a broad range of alloys with diverse mechanical, thermal, and electrical properties, making it a compelling option for both substrate and plating material. Aluminum plating is valued in industries such as electronics, aerospace, and automotive for its light weight, formability, and cost-efficient corrosion protection. The 1000 series aluminum alloys exhibit outstanding electrical and thermal conductivity as well as natural corrosion resistance, whereas 7000 series alloys—zinc and magnesium-based—are prized for strength and durability in high-stress applications.
Despite its advantages, aluminum’s tendency to rapidly form an inert oxide layer poses challenges for achieving strong adhesion during plating. Issues such as inconsistent grain structure and potential for poor bonding require specialized surface treatments before application.
Plating processes for aluminum—including immersion plating, electroplating, and electroless plating—focus heavily on preparing the metal surface to mitigate oxide layer interference. The most common preparatory technique is zincation, which deposits a thin zinc immersion layer to facilitate subsequent metal adhesion. This enables successful plating for electronics, automotive connectors, and EMI shielding housings.
Copper plating remains vital for industries prioritizing electrical and thermal conductivity, such as electronics, power transmission, printed circuit board (PCB) fabrication, and renewable energy systems. The process is valued for its cost-effectiveness, rapid plating rates, and ease of application to complex shapes. Copper underplating can improve the adhesion of subsequent metallic layers, making it foundational in multi-layer finishing systems, as well as being used as a decorative or functional surface in architectural hardware.
There are three main copper electroplating bath types:
Safety and process monitoring are critical for compliance due to regulatory scrutiny of certain chemicals involved in copper electroplating.
Gold plating utilizes electrolytic or chemical methods to deposit pure or alloyed gold onto other metals. It is valued for its exceptional resistance to oxidation, unmatched electrical conductivity, and naturally inert biocompatible surface. As a result, gold plating is highly sought after for fine jewelry, luxury watchmaking, electronic contacts, circuit board connectors, and medical devices.
For functional engineering applications, a nickel or copper strike is commonly used as an intermediate layer to improve adhesion and prevent tarnishing, particularly when plating over copper. The deposited gold layer’s thickness, purity, and bath chemistry are tailored for intended use, whether in high-reliability electronics, aerospace components, dental implements, or decorative objects.
Silver plating is preferred for its superior heat and electrical conductivity—often exceeding gold—and cost-effectiveness. Commonly used in power generation, switchgear, telecommunications, aerospace engineering, and high-temperature mechanical assemblies, silver also provides anti-galling properties to fasteners and bearings. Advanced silver plating techniques support multi-layer coatings for increased wear resistance, improved solderability, and enhanced durability in harsh environments.
Silver’s practical applications include plating on copper for power distribution bars or RF/microwave components, as well as on stainless steel for high-temperature lubricity in industrial and automotive assemblies. The process overcomes oxide film challenges on stainless substrates through pre-plating chemical etching or activation.
Although silver can tarnish due to sulfur compounds, its tarnish layer is readily removed and typically does not impair electrical contact quality. However, in high-humidity environments, measures such as anti-tarnish sealants or alternative coatings may be warranted to prevent flaking or cracking and maintain long-term performance.
Tin plating is widely adopted throughout the manufacturing sector for its non-toxic nature, superior solderability, and reliable corrosion protection. As a soft, silver-white metal, tin is ideal for plating electrical connectors, bus bars, battery terminals, and food-grade components such as cans and kitchenware. Tin's high ductility allows uniform coating even on complex or delicate parts, while its innate corrosion resistance extends the lifespan of plated surfaces. Tin plating is essential in electronics and food processing applications, providing robust protection and maintaining product integrity.
The tin plating process includes surface cleaning, electroplating with controlled current and bath composition, and optional post-treatments like passivation to improve stain or friction resistance. Adjusting the plating process—duration, temperature, and current density—affects layer thickness and functional performance, ensuring suitability for a wide variety of end-use environments.
Rhodium plating (rhodium electroplating) is valued in luxury goods and electronics for its dazzling white finish, outstanding scratch resistance, low friction, and superior resistance to tarnish. Most commonly used to coat white gold, platinum, or silver jewelry, rhodium plating provides a highly reflective, durable surface. The technology is also adopted for select electronic contacts and optical instruments, as well as art and decorative items where long-lasting luster and surface hardness are desired.
Rhodium’s naturally thin deposited layers eventually wear away due to abrasion with prolonged use. Routine maintenance—often every few years—restores the appearance and protective characteristics. With its high melting point and inertness, rhodium plating remains a premium solution for jewelry finish and specialized industrial optics.
Advances in surface engineering have made metal plating on plastic a practical technique for enabling electrical conductivity, shielding against electromagnetic interference (EMI/RFI), and augmenting surface durability and aesthetics of molded components. Both electroplating and electroless plating can be utilized to deposit metals such as copper, nickel, chromium, or even gold and silver onto plastic substrates, adding value in the electronics, automotive, and appliance industries.
Certain engineering plastics—especially thermoplastics like ABS, polycarbonate, and polyether ether ketone (PEEK)—are preferred for their heat resistance, dimensional stability, and compatibility with plating chemistries. Plating on plastic allows designers to achieve lightweight, corrosion-resistant, and visually appealing components that rival metal parts while reducing cost and weight.
Achieving strong metal adhesion on plastics involves several critical surface treatment steps. Typically, the process begins with chemical etching, often using chromic acid, to roughen and activate the surface. After thorough rinsing to remove all residues, the plastic is sensitized and activated with palladium and tin salt solutions to promote catalytic metal nucleation. Subsequent electroless copper or nickel plating establishes a conductive layer, enabling further thickening or decorative finish via conventional electrolytic metal plating. Strict quality control is required to maintain consistent thickness, adhesion, and coverage across all shapes and sizes.
| Plastics That Can Be Metal Plated | |
|---|---|
| Thermoplastics | Thermosets |
| Acrylic | Araldite |
| Acrylonitrile Butadiene Styrene (ABS) | Bakelite |
| Nylon | Epoxy |
| Polylactic Acid (PLA) | Faturan |
| Polybenzimidazole (PBI) | Furan Resin |
| Polycarbonate (PC) | Melamine Resin |
| Polyether Sulfone (PES) | Novolak |
| Polyoxymethylene (POM) | Phenol formaldehyde resin |
| Polyether ether Ketone (PEEK) | Polybenzoxazine |
| Polyetherimide (PEI) | Polyester |
| Polyethylene (PE) | Polyester resin |
| Polyphenylene oxide (PPO) | Polyhexahydrotrianzine |
| Polyphenylene sulfide (PPS) | Polyisocyanurate |
| Polypropylene (PP) | Silicone |
| Polystyrene (PS) | Urea-formaldehyde |
| Polyvinyl Chloride (PVC) | Vinyl ester resin |
| Polyvinylidene Fluoride (PVDF) | |
| Teflon (PTFE) | |
| Polyimide | |
When evaluating options for metal finishing, consider key factors such as environmental exposure (corrosive, marine, high-temperature), electrical or thermal conductivity requirements, expected wear and abrasion, decorative versus engineering needs, and industry compliance standards (e.g., RoHS, REACH). Consulting with experienced plating service providers or manufacturers can help identify the optimum plating system, ensuring reliable adhesion, long-term durability, and cost-effectiveness for your parts or products.
Whether for function, aesthetics, or compliance, tailored metal plating solutions deliver enhanced product performance and value for virtually every major industry.
This chapter will explore the various uses and advantages of metal plating.
The applications of metal plating are:
Many airplane parts undergo electroplating to apply a sacrificial coating that extends their service life by reducing corrosion rates. Aircraft components, which experience significant temperature fluctuations and environmental exposure, benefit from an extra metal layer added to the underlying metal substrate for enhanced protection.
This approach is intended to preserve the functionality of parts by minimizing wear and tear. In the aerospace industry, many fasteners and steel bolts are coated with chromium through electroplating to ensure durability and reliability.
Biodegradable objects such as branches, flowers, and insects are frequently transformed into long-lasting art pieces through metal plating. This technique enhances and preserves the fine details of items that would otherwise decompose. Additionally, digital designers sometimes use electroplating to create durable sculptures.
Designers can create 3D substrates using a desktop 3D printer and then apply electroplating in materials such as gold, silver, or copper to achieve the desired finish. This combination of 3D printing and electroplating results in cost-effective and straightforward manufacturing while maintaining the intended appearance of the final piece.
Electroplating is widely used in the automotive sector, with many leading car manufacturers employing it to produce chrome bumpers and various metal components. Additionally, it is used to craft custom parts for prototype vehicles.
Vehicle customization and restoration shops frequently use electroplating to apply chrome, nickel, and other finishes to various motorcycle and car components.
Electroplating plays a significant role in the jewelry industry. Jewelry designers and manufacturers use this technique to improve the durability, visual appeal, and color of various pieces, including bracelets, pendants, rings, and other items.
Jewelry labeled as silver or gold plated is often the result of electroplating. Different metals are combined to achieve distinctive finishes. For example, copper, silver, and gold are frequently blended to produce the popular rose gold hue.
Electroplating is utilized to add durable coatings to various dental and medical devices. Gold plating is particularly common for making dental inlays and supporting various dental procedures.
Implanted components, such as screws, plates, and artificial joints, are often electroplated to enhance their corrosion resistance and compatibility with pre-insertion sterilization. Additionally, surgical instruments and medical tools, including radiological equipment and forceps, are frequently subjected to electroplating.
Electroplating is commonly used to coat various solar and electrical components to enhance their conductivity. This process is routinely applied to the contacts of solar cells and various types of antennas. Wires, for instance, are often electroplated with nickel, silver, or other metals to improve their performance.
Gold plating is frequently employed, often in combination with other metals, to boost the durability of components. Gold is particularly valued for its ability to extend the lifespan of parts due to its excellent conductivity, malleability, and resistance to oxidation.
Traditional manufacturing methods for producing custom or low-volume metal parts can be both time-consuming and expensive, especially for prototyping. To address these challenges, engineers often combine electroplating with 3D printing to provide a more efficient and cost-effective solution.
Antennas require electrical conductivity to effectively transmit radio waves. While 3D-printed parts do not conduct electricity, they provide exceptional design flexibility and possess advantageous thermal and mechanical properties. By combining these 3D-printed components with electroplating, desired conductivity can be achieved. This approach offers an excellent solution for custom antennas used in research and development across defense, education, medicine, and automotive sectors.
The benefits of metal plating are:
Electroplating offers several advantages, including enhanced strength, conductivity, and longevity of components. Various professionals, such as manufacturers, artists, and engineers, leverage these benefits in different ways. Engineers often use electroplating to boost the durability and robustness of their designs.
Applying a metal coating, such as nickel or copper, can significantly increase the tensile strength of parts. This metallic layer enhances resistance to environmental factors like UV exposure, chemical contact, and corrosion, making the components more resilient in various applications.
Artists utilize electroplating to preserve natural elements prone to decay, such as leaves, transforming them into durable art pieces. In the medical field, electroplating is employed to create implants that resist corrosion and can be effectively sterilized.
Electroplating is also effective for adding decorative metal finishes to consumer products, figurines, sculptures, and art pieces. Additionally, manufacturers often choose electroplating for substrates to produce lightweight parts that are more cost-effective and easier to transport.
Moreover, electroplating enhances conductivity. Since metals are inherently conductive, electroplating improves the performance of electrical components, antennas, and other parts by increasing their electrical conductivity.
Despite its many advantages, electroplating comes with challenges, including hazardous conditions and process complexity. Workers involved in electroplating may be at risk of exposure to hexavalent chromium if safety measures are not strictly followed. Adequate ventilation is crucial to protect workers in these environments.
Structural plating is particularly challenging, requiring multiple baths, extended plating times, and precise metal compatibility. Due to the associated risks and the level of expertise needed, many designers and engineers choose to collaborate with specialized third-party electroplating manufacturers.
This article presented a discussion of the different types of processes of metal plating such as electroplating, electroless plating, and immersion plating. It also presented a discussion of the different types of metal plating based on the metal used, for example it presented on nickel plating, zinc plating, rhodium plating etc. each process of metal plating offers its own unique advantages as well as its drawbacks. For example electroplating requires the application of an electrical current from a power source while electroless plating does not require the passing of an electric current. The different types of metal plating based on the metal used offer different benefits and drawbacks, for example gold plating offers an advantage of no interaction with oxygen and high resistance to conductivity. When choosing a type of metal plating, one has to be aware of the requirements of the metal plating process as well as the properties of the metal that is going to be used for the coating.
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