This article aims to offer you an introduction into questions like “ what is electroplate” and “how does electroplating work”. Electroplating is the application of an electrochemical process to apply a thin metal coating, adhered to the surface of any conductive material or component.
The surface to be covered is set up as the cathode in an electrolytic or galvanic cell, and the metal that is applied is delivered either directly from the anode material, or from the electrolyte solution.
The purpose of this is to apply a decorative, corrosion protective or chemically active coating to alter the properties or reactions of the base part.
These processes are technically simple to perform at a basic level, but can pose a range of difficulties when high quality results are needed. However, the electroplating sector is becoming increasingly widespread and heavily used.
Most forms of electroplating operation are relatively low cost to establish, and often highly profitable. Various types and grades of subcontract suppliers are available in most markets, so when you need electroplated parts there are low friction routes to deliver high quality outcomes.
Electroplating is widely applied in diverse industries, for functional and cosmetic benefits. These include jewelry, medical equipment and implats, electronics, aero and road engine parts and many more fields.
There are also simple home-use solutions that can produce surprisingly good results in decorative applications like Gold plating.
Electroplating is a simple way to add appearance value or surface functionality to lower cost parts, boosting their vue through cosmetic or functional improvement.
Electroplating is used to improve:
- Applying Gold or Silver to base metals is an easy way to add the appearance of higher value
- Many types of electroplating offer protection against corrosion
- Special surface properties such as tensile strength or catalytic
Electroplating the application of a film of one metal onto another (or a conductive non-metal) by hydrolysis, for decorative and/or functional purposes.
Various metals are applied in basically the same process, to achieve these ends – and it is common for plating to be a multi stage process to achieve good adhesion and well integrated coatings.
Electroplating allows manufacturers to use low cost materials such as Carbon steel for the functional structure of components and then coat these to improve appearance, corrosion resistance and various other properties, as required.
What is Electroplating?
Electroplating uses current flow to apply metal atoms to a conductive surface. This is a crystalline application of metals by hydrolysis, as the part is added as an electrode in a cell, and the current flow in that cell is carried by the movement of metal ions through the electrolyte.
Electroforming is a form of electroplating that grows the entire part inside a mandel, by electrodeposition.
Major Electroplating Techniques
Two forms of electroplating cell are used their electrochemistry differs in detail, but they essentially function in the same way:
1) In the simplest and most common electrochemical plating cell, the source metal anode is connected to the positive terminal of a generally DC supply, and the cathode (metal part to receive plating) is connected to the negative.
Both terminals are then immersed in an electrolyte and the current is switched on. When power flows between the electrodes in an ionic current flow, the atoms of the source metal in the anode ionize and dissolve in the electrolyte solution.
The current is carried as charge on these ions, which are attracted to the cathode. These ionized and in-solution metal atoms are then deposited at the cathode by a reduction process, coating the surface. Control of the applied current defines how fast
2) In the less commonly used cell type, the metal ions are already present in the electrolyte and they are depleted as the current flows.
Current flow produces a reduction reaction of metal ions which are already dissolved into the electrolyte, deionizing and depositing metal atoms from the electrolyte and onto the anode surface.
In this form, the cell will generally have a Carbon anode, which will only slowly degrade. However, the metallic ions in the electrolyte will be depleted and the capacity of the cell will fade, making full depletion of the metal content in the electrolyte a diminishing-return process.
Electroplating Material Options
1) Rhodium plating is used for decorative purposes, as it makes jewelry lustrous white/silver and very hard wearing/scratch resistant.
2) Palladium plating is used as a capping layer on Copper and Copper alloy parts before Gold plating. Copper can diffuse directly through the Gold plating, where Palladium provides a barrier to this diffusion, making the Gold plate degrade less.
Selection of plating materials depends on the specifics of the application, intended properties of the plated surface and cost considerations. Here are some commonly used electroplating materials:
3) Gold plating results in excellent corrosion resistance, high electrical conductivity and cosmetic appeal in appearance.
It is commonly used in the electronics industry for plating printed circuit board tracks and connector parts, in jewelry to add appearance value to base metals, and in high end SKUs of devices such as tap ware.
4) Silver plating improves the appearance and corrosion properties of base metals, plus improving electrical conductivity. It is commonly used in the electronics industry, electrical contacts, and tableware/decorative metal goods.
5) Nickel plating offers excellent corrosion resistance, wear properties and it serves as the base layer for subsequent plating with higher cost metals. It is commonly used in the automotive industry, plumbing fixtures, and hardware as the base layer.
Nickel is often applied in electroless plating to improve surface properties before application of other metals by electroplating.
6) Copper plating gives good electrical conductivity and corrosion resistance, and is commonly used as a base layer for subsequent plating.
It is most widely used as the first adhesion layer in Chromium plating, and it is widely used for temporary corrosion resistance in steels, particularly for MIG welding wire.
7) Tin plating results in good corrosion resistance and solderability, so it is most commonly used in the electronics industry to plate the solder points of through hole and surface mount components.
It is also used as a cost reduced coating for printed circuit board Copper tracks.
8) Zinc plating is very widely used for its excellent corrosion resistance on steel parts and is commonly used in the construction and automotive sectors for rust protection.
Most steel roofing and steel car bodies are Zinc plated before painting, to significantly extend the corrosion resistance of these materials.
9) Chrome plating delivers corrosion resistance, wear resistance and cosmetic benefits. It is commonly used in the automotive industry, bathroom fixtures, and decorative items.
‘Hard’ Chromium plating is widely used as a surface hardness and abrasion resistance enhancement for a wide range of engineering parts that suffer chemical attack or abrasive conditions.
10) Cadmium plating was widely used for protection of steel parts, as it retains great ductility making it tolerant of post work without cracking.
Cadmium is considered highly toxic and it is now only used in machine parts for its particular properties in corrosion resistance, ductility and self lubricating characteristics.
The Benefits of Electroplating
Electroplating has various benefits and is a widely used process in many sectors:
- Electroplating applies a low reactivity surface coating layer on the surface of conductive parts, reducing oxidation and other chemical degradation. This prolongs the functional life of products ranging from spectacle frames to rocket combustion chambers.
- Improved aesthetics in the appearance of parts add appearance value. Many decorative applications, such as jewelry, automotive parts, and household appliances benefit from this – combined with touch resilience, as human skin is mildly corrosive.
- Improved electrical conductivity of materials adds functional value in electronic components and switchgear.
- Wear resistance is often improved by hard or self lubricating plating, making parts more durable in high-friction environments, such as engine components, bearings and gears.
The Limitations of Electroplating
While electroplating offers a range of useful and high value benefits, there are limitations to the processes.
Here are some of the limitations of electroplating:
- Only very thin layers of material can be deposited onto a substrate. Thicker coatings may require multiple plating cycles or other coating methods, which increases costs.
- Poor preparation and bad cell design can result in uneven application of plated metals, which can have serious functional and cosmetic consequences.
- Many electroplating processes use toxic chemicals and generate hazardous wastes, so processes must be performed with regard to operator safety and waste materials must be treated as very toxic. Good waste management and disposal practices are critical to minimizing the environmental impact.
- Non conductive materials can only be electroplated after a conductive surface has been added. For example plastics and ceramics cannot be electroplated directly, and may require an electroless metal layer, or a graphite coating, to provide a conductive substrate.
- Good quality electroplating can be expensive, especially for high-volume production or for plating with expensive metals like gold or platinum. The added cost for plated plastic parts often exceeds the component cost significantly.
- The substrate surface must be properly prepared before electroplating to ensure good adhesion and uniform coverage. Plating will amplify surface defects, so high grade mirror polish is required in order to achieve mirror finish in the post plated surface.
The Many Applications of Electroplating
Electroplating is among the most widely used technologies in the manufacture of products.
It has wide ranging uses across most industries:
Electroplating is widely used in the aerospace sector, for various purposes – the least of which is cosmetic:
- Aerospace components encounter harsh environments such as high altitude, extreme temperatures, and corrosive attack. Electroplating provides a protective layer on the surface of airframe and engine components, reducing corrosion and improving durability.
- Self lubrication and hard wearing surfaces are important in moving parts in gears, bearings and actuators and these result from electroplating.
- Electroplating with a high thermal conductivity material like copper or silver assist in dissipating heat from electronics.
- Electromagnetic interference (EMI) and radio frequency interference (RFI) shielding is highly critical in aerospace navigation and comms equipment. Conductive coatings facilitate these functions without adding much weight.
The aerospace sector makes high demands on material performance, and electroplated coatings are a reliable and effective way to meet these demands.
Art and Home Decor
Decorative coatings on a wide range of art and home decor components rely on Gold and Chromium plating.
The automotive sector makes heavy use of electroplating:
- Decorative/corrosion protection applications use Chromium plating for weather facing and skin touch exposed parts, to make durable and stable cosmetic surfaces.
- Engine parts in critical areas are commonly electroplated to enhance corrosion or wear resistance.
- Exhaust components are commonly plated for extreme corrosion resistance, allowing use of lower cost base metals for the structure. In particular, much research effort is applied to the use of plated precious metals in catalytic converters, to provide the catalyst reaction without use of such large quantities of expensive materials.
Jewelry makes extensive use of electroplating in Silver, Gold and Rhodium, to add appearance value (and improved wear/corrosion properties) to lower value materials.
In some cases, there is a decision to make in jewelry production, choosing electroforming vs electroplating onto a pre-made part.
Medical and Dental
Electroplating of elastomeric casts is used in making dies for casting polymer and ceramic parts. It is also used for applying biologically inert coatings to implants.
Electroplating is widely used in the manufacture of switchgear, to reduce ablation rates due to arcing and corrosion induced by high current applications. Power transmission systems and components are widely exposed to open air environments, so electroplating is used to provide environmental protection by steel plating exposed structures.
Prototyping of parts can often require electroplating, for cosmetic and functional purposes. Where prototype parts are metal, they can be directly electroplated.
Plastic parts either require conductive additives in the 3D print material or a conductive coating to be applied. Such a coating can be, for example, electroless Nickel plating – but adequate results can also be achieved using graphite application, where the prototypes are not subject to heavy use.
Get Aesthetic Metal Parts With Kemal’s Finishing Services
The Kaemal team is highly experienced in the manufacture of metal parts by various processes (CNC machining, casting, forging etc.) and we have deep knowledge in the perfecting of such parts with decorative and functional plating.
Whether your need is black Chromium plating on plastics, Gold plating on brass, hard Chromium on bearings and actuator parts or other, more obscure requirements, we will be pleased to hear from you and we are ready to explore how our services and your needs converge.