The Complete Anodising Process Part 2: The Actual Anodising Process

In part two of our series The Complete Anodising Process, we explore the magic of anodising and its colourful possibilities – the actual anodising process. This includes anodising for a clear (natural) finish, and the range of colours available through Astro Anodising. We also address anodising for specific industries. If you didn’t manage to read part one in the series which addressed surface preparation and the importance of proper jigging as well as masking you can read it HERE.

Clear / Natural Anodising

Anodising is a versatile surface treatment that can enhance the appearance and properties of aluminium. When it comes to achieving a clear or natural finish, the anodising process starts with a fundamental transformation. The first step involves immersing the aluminium substrate in an electrolyte solution and passing an electric current through it. This process creates an oxide layer on the surface of the aluminium. For a clear finish, this oxide layer is typically quite thin, often in the range of 5 to 25 microns (µm).

The clear anodised finish offers several key benefits:

Corrosion Resistance: Firstly, it provides excellent corrosion resistance, protecting the underlying aluminium from environmental factors such as moisture and chemicals.

Protection and Durability: Secondly, it adds a layer of hardness to the aluminium, making it more durable and scratch-resistant. Anodising will not peel or flake because it is actually part of the metal. The surface is hardened and protected, unaffected by sunlight and virtually fade resistant, ensuring extended product life. This is particularly useful in applications where the material may be subject to wear and tear like aluminium frames used in architectural applications in coastal regions.

Aesthetic Appearance: Clear anodising doesn’t change the colour of the aluminium, maintaining its natural appearance while improving its surface properties. This makes it ideal for applications where aesthetics matter, such as architectural elements, automotive parts, and consumer electronics.

Pre-treatment Benefits: Natural anodising is an excellent pre-treatment for paint or powder coated finishes and is highly recommended for coastal applications due to its superior corrosion resistance.

It is important to note that there are a number of conversion coatings available for aluminium pre-treatment. At Astro Powder Coating, we use a chrome 6 pre-treatment process to both enhance adhesion properties and ensure corrosion resistance before the baking step. This reduces the necessity for anodising prior to powder coating.

Customisation through Colour

One of the most intriguing aspects of anodising is the ability to infuse aluminium with a wide range of vibrant colours. This is achieved by modifying the anodising process. Instead of the standard clear anodising, the oxide layer can be grown to a thicker, more controlled thickness, typically in the range of 10 to 25 microns. By doing so, the aluminium can be dyed in various colours during the anodising process.

The range of colours achievable through anodising is extensive and can include everything from bold primary colours to more subtle pastels. This customisability makes anodising an excellent choice for applications where aesthetics are a key consideration, such as architectural facades, automotive components, and consumer products. It is important to note that the coloured oxide layer retains the corrosion resistance and durability associated with clear anodising, ensuring the aluminium’s performance isn’t compromised.

Astro Aluminium’s Colour Range

With our large selection of colours and finishes and our capability to anodise work in sizes ranging from small parts or machined components right up to lengths of 7.5m, Astro Anodising offers the largest selection of colours available in South Africa. Our standard colours are available in either bright or matt options for components up to 3m in length with the exception of green, which is only available for components 500mm x 500mm in size.

Anodising White

Interestingly, you cannot anodise aluminium to produce a pure white colour. However, you can achieve a light or white appearance on anodised aluminium by a few different methods:

Clear Anodising: Clear anodising can make the aluminium appear silver or light grey. It doesn’t create a pure white colour but can provide a bright, reflective finish.

Powder Coating: If you require a true white colour, you might consider clear anodising first and then powder coating. Using this method we first anodise the aluminium to provide a durable and corrosion-resistant base, and then apply a white powder coat to achieve a pure white colour.

Industry Specificity in Aluminium Anodising

Aluminium anodising is not a one-size-fits-all process. Different industries have unique requirements that anodising can address.

Automotive

The automotive sector values anodised aluminium for decorative and functional purposes. Anodised trim, wheels, and interior components offer both a sleek appearance and durability, enhancing the overall look and performance of vehicles.

Building, Construction and Architectural

In the architectural field, anodised aluminium is a popular choice for building facades and interior applications due to its aesthetic appeal and weather resistance. The ability to customise colours allows architects and designers to achieve their vision while ensuring long-term durability. For example, our Aluminium Compensation Channel is a quality, cost-effective aluminium compensation channel designed for the easy installation of glass in interior environments and comes in a range of anodised colours.

Medical

The medical industry benefits from anodised aluminium in numerous ways. One notable application is in the production of prosthetics and mobility devices. Anodised aluminium components used in prosthetic limbs and mobility aids offer several advantages including light weight, durability and corrosion resistance.

Packaging

Anodised aluminium finds its place in the packaging industry due to its corrosion resistance and visual appeal. It is often used for premium packaging solutions for perfumes, cosmetics, and luxury goods. Anodised aluminium packaging not only protects the product but also adds a touch of elegance, making it an ideal choice for high-end brands.

Hospitality – Catering

In the hospitality and catering sector, anodised aluminium plays a role in creating durable and attractive kitchenware and equipment. Cookware, utensils, and food service equipment benefit from the corrosion-resistant, easy-to-clean surface of anodised aluminium, ensuring hygiene and long-lasting performance. Additionally, the ability to customise colours can align with a brand’s identity and aesthetic.

Advertising and Décor – Signage, Framing

The advertising and décor industries often use anodised aluminium for its visual appeal and durability. It is a popular choice for outdoor signage, where it withstands exposure to harsh weather conditions. Anodised aluminium framing is used for art, mirrors, and decorative elements due to its lightweight nature, corrosion resistance, and the option for custom colours, providing versatility in design.

Aerospace

In the aerospace industry, anodised aluminium is often used to protect components from the harsh conditions of high altitudes and extreme temperatures. The corrosion resistance and lightweight nature of anodised aluminium are key advantages in this context.

Renewable Energy

Anodised aluminium is used in the renewable energy sector, particularly in battery technology and hardware/component requirements. It is an essential component in the construction of aluminium-air batteries and anodised aluminium is widely used in solar panel frames and mounting systems. Anodising protects the aluminium components from chemical reactions and environmental factors, ensuring the longevity and efficiency of these energy storage solutions.

Consumer Electronics

Anodised aluminium is widely used in the manufacturing of smartphones, laptops, and other consumer electronics. The process not only enhances the appearance but also provides a durable, scratch-resistant surface that can withstand daily wear and tear.

Conclusion

The beauty of anodising lies in its versatility. The anodising process and the vibrant array of colours it offers provide a remarkable fusion of form and function. It’s not just about transforming the appearance of aluminium; it’s about enhancing its performance and protection.

Stay tuned for part 3 in our series, where we go beyond anodising to understand the importance of sealing, quality inspection, and packaging and handling – crucial steps in the post-anodising process which significantly impact the final quality, performance, and overall customer satisfaction of anodised products.