Hard Anodising vs. Natural Anodising: Key Differences & Applications
Aluminium is widely used in various industries due to its lightweight, corrosion resistance, and versatility. However, to further enhance its properties, anodising is applied as a protective and functional surface treatment. Two of the most common anodising processes are Natural Anodising and Hard Anodising, each with distinct characteristics suited for different applications.
This article explores the differences between hard anodising and natural anodising, their benefits, and their ideal applications to help you choose the right anodising process for your needs.
What is Natural Anodising?
Natural anodising, also known as standard anodising or Type II anodising, is an electrochemical process that creates a thin oxide layer on the surface of aluminium. This layer enhances corrosion resistance, improves aesthetics, and allows for colour anodising, making it ideal for applications requiring both protection and visual appeal.
Key Features of Natural Anodising:
✔ Typical coating thickness: 5–25 microns
✔ Enhances corrosion resistance
✔ Can be dyed in a range of colours
✔ Lightweight, with minimal impact on dimensions
✔ Ideal for decorative and functional applications
Applications of Natural Anodising:
Architectural Components – Window frames, cladding, decorative aluminium panels
Consumer Electronics – Laptop casings, smartphone bodies, and home appliances
Automotive & Motorsport – Interior trims, branding plates, and lightweight components
General Engineering – Components requiring moderate protection with aesthetic finishes
What is Hard Anodising?
Hard anodising, also known as Type III anodising, is a more advanced and intensive anodising process that produces a thicker, denser, and harder oxide layer on aluminium. This process takes place at a lower temperature and higher voltage, creating a surface that is highly resistant to wear, corrosion, and extreme environmental conditions.
Key Features of Hard Anodising:
✔ Typical coating thickness: 25–100 microns
✔ Exceptional wear and abrasion resistance
✔ Increased surface hardness, comparable to hardened steel
✔ Superior corrosion resistance, even in extreme environments
✔ Typically results in a dark grey or black finish (limited colour options)
Applications of Hard Anodising:
Aerospace & Defence – Hydraulic cylinders, landing gear components, and precision-engineered parts
Motorsport & Automotive – Brake calipers, engine components, and suspension parts
Medical & Pharmaceutical – Surgical instruments and sterilisation trays
Industrial & Engineering – Gears, valves, and parts subject to mechanical wear
Food Processing & Marine – Cookware, food-grade equipment, and corrosion-resistant parts
Key Differences Between Hard Anodising & Natural Anodising
| Feature | Natural Anodising (Type II) | Hard Anodising (Type III) |
|---|---|---|
| Thickness | 5–25 microns | 25–100 microns |
| Wear Resistance | Moderate | High (Comparable to hardened steel) |
| Corrosion Resistance | Good | Excellent (Ideal for extreme environments) |
| Aesthetic Options | Wide range of colours available | Limited (Dark grey to black) |
| Surface Hardness | Moderate | Very High |
| Applications | Decorative and light-duty functional parts | Heavy-duty, high-wear industrial parts |
Choosing the Right Anodising Process
When selecting between natural anodising and hard anodising, it is essential to consider the operating environment, functional demands, and aesthetic requirements.
Choose Natural Anodising if:
✅ The primary need is corrosion protection with an attractive finish.
✅ The component requires colour anodising for branding or aesthetic appeal.
✅ The application does not involve extreme mechanical wear.
✅ The lightweight properties of aluminium must be maintained.
Choose Hard Anodising if:
✅ The part will be exposed to abrasion, friction, or mechanical wear.
✅ The application requires maximum corrosion protection, such as marine or aerospace environments.
✅ Surface hardness and durability are critical.
✅ The part must perform under high temperatures or chemical exposure.
Conclusion
Both hard anodising and natural anodising play essential roles in enhancing the performance, lifespan, and appearance of aluminium components. The right choice depends on the specific needs of your application—whether it's aesthetic appeal and moderate protection (natural anodising) or superior durability and wear resistance (hard anodising).
At RMC Anodising Ltd, we specialise in both hard and natural anodising, offering tailored solutions to meet industry standards and customer specifications. Contact us today to discuss your anodising requirements!
