Table of Contents

metal plating for cnc machined parts

A Detailed Guide to Metal Plating: Working Principle, Types and Techniques

Product designers and manufacturers utilize various metal finishes for custom parts. Most of these finishes enhance products’ physical appeal while others improve functionality. Metal plating offers a distinct combination of properties that make custom products more suitable for the intended application.

Metal plating is a practical post-production finishing option and a critical aspect of modern technology, which makes it ideal for various applications and compatible with different metals.

This guide delves into the surface plating surface finish process and its working principles, exploring this technique’s fundamental elements and how to achieve the best outcomes!

What Is Metal Plating?

custom gold plating automotive wheel
Custom Gold Plating Automotive Wheel

Metal plating is a surface finishing treatment that involves depositing metals such as nickel, copper, gold, or other metals on the substrate or workpiece. It is commonly used to coat metal and other materials to make them aesthetically appealing and protect them from corrosive elements by forming a thin layer of metal over them.

This finish can be achieved with electroplating or electroless plating. Metal plating offers extensive benefits, including reduced chances of corrosion, decreased friction, improved conductivity, improved surface roughness, better paint adhesion, solderability, and strength.

Step-by-Step Guide to Metal Plating Process

principle of metal plating
Principle of Metal Plating

Metal plating custom products involve a series of pretreatment and post-treatment steps. While there are different metal plating techniques, we will explore the basic procedures of electroplating in this section:

STEP I: Pretreatment

The pretreatment ensures the removal of all contaminants on the metal surface that may complicate the plating process. This step involves cleaning, rinsing, and other pretreatment that help remove harmful contaminants from the plating surface. Although some base materials require only one cleaning, others may require two or more to ensure the removal of all contaminants.

STEP II: Determine the Effectiveness of the Cleaning

The ideal plating technique depends on the requirements of your custom parts. Also, it determines how clean your plating surface should be before the process occurs. For instance, you need to remove only bulk soil and dirt with some CAD plating techniques, while others require removing oil and grease. Therefore, you can check your substrate’s cleanliness with a water break test, reflectivity, or wipe test to ensure the surface of the base material is free from any residue.

STEP III: Prepare the Plating Station

Since the focus is on electroplating, you need a tank, a rectifier or other source of direct current, an anode, a cathode, and a compatible plating solution to prepare a plating station for your products.

STEP IV: Plating

Metal deposition begins once you turn on the electrical current. However, to achieve a thicker finish, you must expose the plating surface to the current longer. Temperature, immersion durations, voltage levels, etc., are variables to consider when plating substrates.

STEP V: Post-treatment

Post-treatment cleaning is critical after creating the preferred deposition on the products. More so, electrolytic polishing effectively improves manufactured components’ corrosion-resistant properties.

STEP VI: Waste Disposal

The metal plating finish creates heavy metals, which are often harmful due to their extreme toxicity levels. Therefore, pretreating the plating wastewater before disposal is an efficient disposal method.

Common Metal Plating Techniques for Custom Parts

common metal plating techniques for custom parts
Common Metal Plating Techniques for Custom Parts

There are various metal plating techniques, each with unique procedures and outcomes. Below are typical metal plating techniques used in different industries:

Electroplating

Electroplating is a standard metal plating technique that involves using electric currents in an electrolyte solution to melt charged metal particles (dissolve ions) on the surface of a workpiece. The positive (charged) metal ions bond with the workpiece while the workpiece has a negative charge on the circuit. The dissolved metal particles stay on the material’s surface when the workpiece is dipped in the chemical solution.

Electroplating improves the mechanical, chemical, and physical attributes of a workpiece. This plating method forms a thin, uniform, quick, and smooth protective layer of desired metal or alloy on a workpiece, improving its aesthetic and functionality.

Immersion plating

The metal immersion plating technique involves submerging a metal workpiece into a chemical compound containing metal ions of a noble metal. The noble metal’s ion is often stable; hence, a natural pull occurs, displacing the metal’s ion from the initial metal to create a thin layer of noble metal ions. However, this process can be more time-consuming than the electroplating process, and it works well with only noble metals such as silver, platinum, and gold.

Electroless

The electroless (autocatalytic) plating is a cost-efficient and straightforward alternative to electroplating. Since it doesn’t need any external electric current, it is often called autocatalytic or chemical plating. Electroless plating utilizes a reducing chemical bath to form metals like nickel, copper, silver, and gold on the surface of several materials. Since electroless plating is a chemical process that doesn’t require electricity or machinery, it creates catalytic reduction to the path.

Electroless plating is ideal for complex surface components with good corrosion resistance. Therefore, manufacturers in the oil and marine industries use this metal plating technique to finish components for their applications. Standard components like pumps or valves typically exposed to corrosive elements and environments are finished with electroless plating technology.

Carburizing

This type of metal plating solidifies the surface of metal components while allowing the base metal to maintain its softness. Carburizing or surface hardening forms a thinner, solid metal coating called the surface case.

Since carburizing makes element contents harder, product designers often carburize parts machined to their final form harder. This metal plating technique helps make metal components and machinery used in industries more corrosion-resistant.

Plasma Spray Coating

Plasma spray coating involves spraying melted or heat-softened material on a workpiece’s surface to achieve the desired coating. This technique is typically effective and flexible because it uses a sophisticated spray coating technology that facilitates spraying various materials, including cermet, ceramic, and metal. Jet engine protection and restoring worn parts are typical plasma spray coating technology applications. It offers excellent resistance to oxidation, wear, heat, abrasion, and electricity.

Physical Vapor Deposition (PVD)

This metal plating type is a thin film preparation technique that physically melts the surface of a material source (solid or liquid) molecules, gaseous atoms, or into ionized into ions under vacuum conditions. A coating with a particular function is deposited on the substrate’s surface with a low-pressure plasma or gas.

Sputtering deposition, vacuum evaporation, ion plating, arc plasma plating, etc, are essential PVD technologies that manufacturers use. PVD coatings have an extensive application range and provide strong adhesion, rapid deposition, and excellent diffraction.

Standard Metal Plating Finishes

standard metal plating finishes
Standard Metal Plating Finishes

Product designers employ several standard industrial plating finishes to achieve the desired results. Below are the commonly used metal plating types:

Copper plating

copper plating tube
Copper Plating Tube

Copper is a cost-efficient plating material famous for its high conductivity. Copper plating is ideal for electronic components like circuit boards. Product designers commonly use it due to its low material cost and high plating efficiency.

Chrome plating

at machining plating chrome
AT-Machining Plating Chrome

Chrome plating (Alodine finish) uses chromic to create a coating layer on metal components with chromic acid and trivalent chromium baths. Manufacturers employ chromium plating primarily for aesthetic enhancement of their products.

Besides, chromium plating finishes increase the corrosion resistance property of substrates because it increases the material’s hardness. Iron and steel parts are often plated with chromium due to their high compatibility, which can restore tolerance on worn-out parts. Parts finished with chrome plating are perfect for industrial applications.

Tin plating

This plating type involves depositing. Tin plating is a cost-effective electroplating process since the material is cheaper and readily available than other metals such as platinum, gold, or palladium.

Gold plating

Gold metal plating is widely embraced in the electronics and jewelry industry due to its oxidation resistance and high electrical conductivity. This plating type effectively transfers the remarkable properties of gold to metals such as silver and copper. Similarly, gold plating helps to enhance the conductivity of electronic components such as electrical connectors.

Rhodium plating

This alternative metal plating finish creates a thin rhodium coating on the surface of products such as jewelry. This plating type is also referred to as rhodium flashing or rhodium dip. It enhances a piece of jewelry’s light reflection, luster, and durability.

Nickel plating

electroless nickel plating cnc parts
Electroless nickel plating CNC Parts

Nickel plating is another commonly used and valuable electroless plating technique. It helps to develop a protective layer on household products, including shower fixtures, doorknobs, and cutleries. Electroless nickel plating improves the aesthetics and wear resistance properties of plated components. Although it is best suited for plating copper and aluminum components, it is compatible with other metals, acting as a basic plating for chromium

Silver plating

silver plating parts
Silver Plating Parts

This industrial finish is similar to gold plating because it improves the plated material’s aesthetic appeal. It is an ideal choice for applications where electrical conductivity is a critical factor. Most manufacturers often employ this metal finish type as an alternative to gold plating due to its cost-effectiveness. Moreover, it is ideal for plating copper products.

Zinc Plating

zinc plating cnc machined part
Zinc Plating CNC Machined Part

Zinc is another cost-effective material commonly used in metal plating. It forms galvanized metal on metal substrates. Manufacturers plate zinc on metal substrate through molten bath dipping and spraying. In this process, the substrate is the cathode, while the metallic zinc is the anode in a soluble zinc salt electrolytic bath. This plating type offers better control over coating thickness and uniformity since it creates a relatively ductile coating on plated metal.

Cadmium Plating

This metal is a metallic silver tender coating with high malleability, chemical resistance, corrosion resistance, and ease of solderability. Due to its combination of desirable material properties, manufacturers often deposit cadmium on various base metals, including iron, aluminum, steel, and copper. The cadmium plating process is suitable for components such as military parachute buckles, bolts, and screws for submarines.

Benefits and Limitations of Metal Plating

benefits and limitations of metal plating
Benefits and Limitations of Metal Plating

Manufacturers and product designers capitalize on the extensive benefits of metal plating to optimize their various designs. Here are some of the expected benefits of metal plating finishes:

  • Metal plating increases a substrate material’s hardness and strength.
  • It is a cost-effective finishing method.
  • Metal plating increases the aesthetic appeal of a workpiece’s material.
  • Various metal plating finishes work well with several materials.
  • Metal plating finishes create a protective barrier on custom products to protect them from environmental factors like UV light, corrosion, or corrosive applications.

Despite the enormous benefits of this post-processing technique, manufacturers experience certain limitations, such as:

  • The metal plating process can take time and compromise the specifications of machined parts.
  • These plating finishes can crack and chip in certain environments because of wear.
  • Personnel overseeing the electroplating process may suffer from hexavalent chromium exposure if proper precautions aren’t taken.
  • Most engineers and designers often resort to hiring a third-party electroplating manufacturer due to the potential dangers and required expertise.

Applications of Metal Plating Finishes

silver plating in medical
Silver Plating in Medical

Manufacturers across various industries adopt different metal plating finishes to best meet their products’ requirements. In this section, we will explore the applications of metal plating finishes in different sectors:

Automotive

In the automotive industry, parts engineers and manufacturers depend on electroplating to create customized parts for concept vehicles. Automotive electroplating enables most vehicle restoration industries and customization businesses to apply chrome, nickel, and other finishes on motorcycle and vehicle parts. Additionally, vehicle manufacturers finish car parts with black oxide coating since it works best for machined parts and is durable.

Aerospace

Electroplating offers desirable properties in the aerospace sector. Manufacturers electroplate aircraft parts to achieve a sacrificial coating, reducing corrosion and increasing their lifespan. Metal plating processes add an extra metal layer to aircraft components to enhance their functionality because they are often exposed to substantial temperature changes and various environmental elements.

Jewelry

Electroplating is a standard metal plating technique in the jewelry industry. Product designers and manufacturers rely on electroplating processes to achieve the desired cosmetic metal finishes, durability, and luster for pendants, rings, bracelets, and other accessories.

Medical

Manufacturers in the medical sector utilize metal plating finishes to improve the toughness of the surface of medical components like dental instruments, protecting them from degradation. Electroplating helps make medical implants compatible with sterilization procedures.

Power

In the power sector, manufacturers electroplate solar components to increase their electrical conductivity. They also electroplate wires with nickel, silver, and other compatible metals. Solar cell contacts and antennas are other metal-plated components in the power industry.

Expert Tips for Successful Metal Plating

electroplatings color reference
Electroplatings Color Reference

Metal plating applies to various industries, from aerospace to jewelry. While properly finished metal surfaces offer a wide range of benefits, such as improved aesthetics, functionality, and durability, they also demand careful consideration and expertise to attain the desired results. Here are factors to consider when plating a substrate:

Pre-Plate Material Condition

Before plating on a material’s surface, it must be in a plating-ready condition to prevent complications. The quality of a surface finish depends on its adherence to the base material, and the smallest buildups can influence the success of the metal coating. For instance, the plated deposit may fail to adhere to a substrate’s surface if it has contaminants like heat treatment scales, oil buildups, oxides, and other residues.

As a result, you can remove these contaminants with pretreatment procedures, which include deoxidizers, acid pickles, alkaline presoaks, vapor blasting, chemical descalers, etc. However, experts recommend bead last finish due to its effectiveness in preparing a plating surface.

Choose the Right Metal Plating Technique and Plating Metals

Various metal plating techniques offer distinct advantages and are compatible with different applications. While immersion plating involves the chemical deposition of the plating material on the substrate, electroplating passes an electric charge through an electrolytic solution to deposit the plating metal on the workpiece surface. Electroless plating is ideal for plating workpieces with complex geometry or non-conductive surfaces and doesn’t require an electric current. Therefore, it is important to examine the product application, type of base metal, and the suitable plating material.

Choosing a plating material is as essential as the plating technique because it determines the finished product’s durability, functionality, and appearance. Experts recommend choosing the appropriate material based on the product’s application and working environment. While chrome plating offers good corrosion resistance, gold plating is known for its excellent electrical conductivity. Nevertheless, low-quality plating materials should be avoided to avoid poor adhesion, inadequate base metal protection, and defects.

Thickness Tolerance

The plating layer’s thickness is a critical factor that influences the quality and functionality of the final product. Corrosion can occur if a plating layer is too thin, and cracking or peeling can occur if it is too thick. Hence, experts advise using specialized tools such as a thickness gauge to monitor the plating thickness throughout the process. However, below are essential tips for achieving the desired maximum and minimum thickness range:

  • In most cases of metal plating, electroplating develops even coating. Hence, tight thickness tolerance will not be an issue.
  • Specify a surface area of the workpiece that needs to remain within a tight metal plating thickness. It is essential to consider geometric parameters such as corners, recesses, etc.
  • Electrolytic plating causes finishes to settle on a plating surface’s region more than others. For instance, plating deposits get thinner within inches of a recessed area. Therefore, using a tight tolerance for flat and simple shapes may be inadvisable.
  • Experts recommend creating checkpoints to determine the plating tolerance requirements. Ensure such checkpoints are positioned on the surfaces where they are ideal.

Conclusion

Metal plating is a post-production process that improves all products’ aesthetics, functionality, and longevity. This technology offers enhanced aesthetic appeal and benefits through various methods and can exploit the properties of different types of metal. If properly executed, metal plating finishes offer superior-quality and durable plated products that exceed the client’s specifications.

at machining surface finishing services
AT-Machining Surface Finishing Services

AT-Machining is the ideal metal finishing solution expert whenever you need professional assistance finishing your custom products with the desired metal coating. Our experienced and expert engineers and product designers offer cost-effective surface finish solutions for many industries. Trust us to work with you to give your products the high-quality and satisfactory finishes they require. Contact AT-Machining today to discuss the details of your project with an expert. Let’s ensure your experience is seamless as you elevate your products!

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