Metal finishing refers to a range of techniques that are used to enhance elements of a metal product and to achieve certain functional and aesthetic results.

What exactly is metal finishing, what are the different types of finishes for metal and what do you need to consider when selecting a metal finishing technique for your project?

What is metal finishing?

Metal finishing is a broad and all-encompassing term that refers to the process by which a variety of coatings, treatments, or processes are applied to the surface of a metal object. Metal finishing aims to improve the appearance, durability or performance of an object. It does this by enhancing the properties of a particular metal, helping to protect it from a range of factors such as corrosion and wear, as well as other environmental conditions. It can also be used to strengthen the substrate and increase resistance to wear, reduce the impact of friction, increase solderability, make a surface electrically conducive, or serve as a primer coat to aid paint adhesion.

Metal finishing can involve various techniques and methods, each of which has been developed to serve their different purposes and desired outcomes. Deciding on the best finishing technique for your project will depend on a range of factors. Understanding these factors as well as the strengths and weaknesses of potential finishes is essential before deciding on the right technique for your particular product.

How does metal finishing work?

There are several finishing methods used to achieve a specific desired result. These use different methods to achieve certain results, each of which differs in complexity, cost and outcomes. It’s important to understand the differences between these techniques to ensure you make the right choice of metal finishing technique for your project.

Some of the more commonly used methods include:

Plating

Plating involves depositing a thin layer of metal, such as chromium, nickel, or gold, onto the surface of a base metal through electrochemical processes. This can enhance the appearance, corrosion resistance, and conductivity of the metal.

Anodising

This is an electrochemical process used to create a protective oxide layer on the surface of aluminium. This layer strengthens the corrosion resistance of the metal and can also be dyed.

Painting & Coating

Applying paint or other coatings to metal surfaces can provide protection against corrosion, UV radiation, as well as other environmental factors. Both liquid painting and powder coating are commonly used methods for metal finishing.

Passivation

This is a chemical process that removes surface contaminants and forms a thin, protective oxide layer on stainless steel. This can improve corrosion resistance and enhance the appearance of the metal.

Galvanising

The galvanising process involves applying a layer of zinc to the surface of iron or steel using a hot-dip or electroplating process. As well as enhancing the appearance of the metal it can also improve corrosion resistance.

Buffing & Polishing

Buffing and polishing are mechanical techniques that use abrasion to smooth the surface of the metal to create a reflective finish and improve its appearance.

Chemical Treatments

A range of chemical treatments such as acid etching, chemical patination, and blackening can be used to achieve specific visual effects and to improve corrosion resistance.

Electropolishing

This is an electrochemical process that removes a thin layer of metal from the surface. This results in a finish that is not only corrosion-resistant but is also bright and smooth.

What are the different types of finishes for metal?

There is a range of different types of finishes for metal available, each of which has unique characteristics and advantages. Some of the most commonly used include:

Mirror Finish

As the name suggests, a mirror finish is highly reflective. It will be free of any visible defects and will usually be achieved through buffing and polishing processes. A mirror finish is often applied to decorative items and is used in architectural applications.

Brushed Finish

A brushed finish is recognisable due to the fine parallel line on the surface. It creates a distinctive look that is often used on appliances, furniture and on other products where a textured appearance is required.

Galvanised Finish

During the galvanisation process, a layer of zinc is applied to iron or steel to provide corrosion resistance. This resistance makes it highly suitable for outdoor structures, industrial equipment and fencing.

Antique Finish

An antique finish gives the metal surface an aged, weathered appearance and is often seen in decorative items, jewellery and other objects. It is achieved through chemical treatments or patination.

Powder Coating

By applying a powder coating to a metal surface you can achieve a durable and vibrant finish. It provides resistance against scratches, chipping and fading, making it ideal for outdoor furniture, vehicle parts and appliances.

PVD

Physical Vapour Deposition (PVD) deposits thin layers of material on the surface of the metal. This provides enhanced wear resistance and is available in a range of colour options. It’s used for a variety of applications including decorative items and cutting tools.

When to use different metal finishes

There is a range of finishes for metal available so it’s important to choose the right one for your purpose. This will usually depend on a number of factors, including the intended use of the finished products, the metal’s properties, how it will be used and the kind of conditions it’s likely to face.

When a metal product is exposed to moisture, harsh environments or chemicals, then corrosion resistance will be key. Usually, this will mean techniques such as galvanising, certain types of plating and anodising.

If you’re looking to create products that can withstand wear and which may be subject to frequent abrasion or fiction, then finishes such as PVD coatings and hard chrome plating may be suitable.

When maintaining effective electrical conductivity is essential, then finishes such as gold or tin plating should be used. These techniques are typically used in electrical components and connectors.

It’s crucial that any items that will be used in high-temperature applications are given a finish that’s capable of withstanding heat without deteriorating. Typically, this will include ceramic coatings or heat-resistant paints.

How to choose the best industrial metal finishing technique

Choosing the right metal finishing technique requires careful consideration of several key factors to ensure optimal outcomes for your project. Each factor will play a significant role in determining the most suitable finishing approach, ultimately impacting the performance, appearance and durability of the finished product.

With a range of metal finishes available, what factors should you consider when making your decision?

Firstly, the type of metal you’re working with will be a pivotal factor in the decision-making process. Different metals possess distinct characteristics that impact how they will respond to different finishing processes. Lightweight aluminium will be used in applications where a balance is required between corrosion resistance and aesthetics. Stainless steel with its high corrosion resistance is a popular choice for environments where harsh chemicals or moisture are prevalent. Iron has a susceptibility to rust and will require finishes that provide robust corrosion protection.

The environment in which the finished product will be used will be a significant factor in the selection of finishing technique. Understanding different environmental factors such as moisture, corrosive chemical, extreme temperatures, abrasive conditions or UV radiation, will each require a different finish. Understanding the purpose of the finished object and the environment in which it will be used will be critical factors when it comes to deciding which metal finishing technique to use.

Different finishing techniques will also vary in cost, ranging from more affordable options such as powder coating to more complex processes such as PVD coating. While more complex finishes may provide you with exceptional results, they may not always be economically viable for some projects.

The scale of your project will also influence the choice of finishing technique. Some processes will be better suited for larger, mass-production projects due to their efficiency, while more meticulous techniques are most appropriate for small-batch and custom projects. In some instances, there may be specific regulations and standards that will determine your choice of finishing technique.

Which metal finishing option is best for you?

Your choice of metal finish will depend on your specific project, your requirements and your priorities. Different finishes for metal will produce different benefits and finishing techniques.

Decorative Items

If your ultimate aim is to enhance the visual appeal of decorative items such as jewellery, furniture or architectural elements, then your focus should be on techniques that enhance this aesthetic appeal.

Mirror polishing will produce a glossy, reflective surface. Brush textures introduce fine parallel lines across the surface, adding depth and texture to your pieces. For a weathered, vintage look then chemical treatments to produce an antique patina may be suitable.

Outdoor Products

When you are creating products for outdoor use, your choice of finish should achieve durability and enhanced corrosion resistance.

Galvanising a product with a protective zinc layer shields against corrosion. It can be an excellent choice for outdoor structures and utility equipment.

Powder coating provides a resilient layer that safeguards against environmental stressors, making it particularly suitable for outdoor furniture and playground equipment.

Electronics

With items used for electronic purposes reliable electrical conductivity and functionality are vital.

Gold or tin plating will frequently be used on connectors, circuitry, and other electronic components. As well as ensuring excellent conductivity they also prevent corrosion, helping to maintain the integrity of electronic connections.

Tools & Machinery

Tools and machinery require finishes that can withstand wear and tear. The aim of any finish is to ensure optimal performance and extend its lifespan.

PVD coating gives the surface a thin, hard layer that provides exceptional wear resistance. This increases durability, making it a good choice for cutting tools, moulds and industrial equipment.

Hard chrome plating provides unmatched hardness and wear resistance. This enhances longevity and improves performance for tools that are subjected to intense abrasion and friction.

High-Temperature Applications

Products that are exposed to high temperatures demand finishes that can endure without deteriorating.

Ceramic coatings can provide excellent heat resistance. They are commonly used in industrial applications, for vehicle parts, and for aerospace components.

Deciding on your choice of metal finish should take into account the intended purpose of the product, as well as the environment in which it will be used. Whether you’re looking for an improved appearance, enhanced corrosion resistance, electrical conductivity, or durability, there is a metal finishing technique that can achieve your desired results.

Metal Finishing Machinery & Advice from Sparx Machine Tools

At Sparx, we are proud to be the UK supplier for brands such as Kuhlmeyer and Baileigh, offering a great choice of metal finishing machinery. If you have any questions about our range of products, would like to discuss your requirements or metal finishing in general, our team would be happy to help.