What is the anodising of aluminium？

Understanding the Anodising Process for Aluminium

Anodising aluminium is an electrochemical process that forms an oxide layer on its surface. This oxide layer provides protection against further oxidation and enhances both the appearance and performance of the aluminium.

Why do we anodise aluminium?

We anodise aluminium to enhance its natural properties, improving its resistance to corrosion, wear, and abrasion while enabling dyeing in various colours for better aesthetics. Anodising provides a durable, long-lasting finish, making it suitable for various applications, from architectural components to consumer electronics.

1. How long does anodized aluminum last?

The aluminium oxide layer formed during the anodising process significantly enhances the corrosion resistance of aluminium. The specific reasons are as follows:

• Density of the aluminium oxide layer: The aluminium oxide layer is highly dense, effectively isolating air, moisture, and other corrosive agents, preventing these substances from directly contacting the aluminium substrate, thereby delaying or preventing corrosion.
• Controllable thickness: By regulating the anodising time and current, different thicknesses of the aluminium oxide layer can be achieved. Generally, the thicker the layer, the better the corrosion resistance.

2.Does anodized make aluminum harder?

The aluminium oxide layer formed by anodising has a high hardness, significantly enhancing the wear resistance of the aluminium surface. Specific characteristics include:

• High hardness: The aluminium oxide layer’s hardness is comparable to corundum (Al₂O₃) and several times greater than the aluminium substrate, allowing anodised aluminium to last longer in high-wear environments. Anodising forms a thin layer of aluminium oxide on the surface, ranging from 5 to 30 microns, while hard anodised coatings can reach 25 to 150 microns.

• Scratch resistance: The surface of anodised aluminium is more difficult to scratch or wear, with a hardness of up to 250 to 500 kg/mm². This makes it suitable for components that require frequent handling or contact, such as mobile phone casings and hand tools.
• Heat resistance: The surface layer of hard anodised aluminium has a melting point of up to 2320 K, demonstrating excellent heat resistance.
• Corrosion resistance: After anodising, the material’s corrosion resistance is enhanced. Experiments have shown that the oxidised product remains non-corrosive in a NaCl salt spray with a concentration of ω=0.03 for several thousand hours. Therefore, the oxidised products can be used in high-concentration acids.

3. Does anodizing change the colour of aluminum?

Anodising not only enhances the physical properties of aluminium but also allows for dyeing treatment to improve its aesthetic appeal. The specific advantages are as follows:

• Diverse colour options: The aluminium oxide layer formed after anodising has excellent adsorption properties, allowing it to absorb various dyes and create a wide range of colours. This means that aluminium products not only serve functional purposes but also possess decorative qualities.

• Uniform surface treatment: The surface treatment of anodised aluminium is very uniform, with no issues of uneven colour or spotting, resulting in an excellent visual appearance.

4. Electrical insulation properties

The aluminium oxide layer has excellent electrical insulation properties, which makes anodised aluminium widely applicable in electronic products. Specific advantages include:

• High resistivity: The aluminium oxide layer has a very high resistivity, with a breakdown voltage of up to 2000 V, effectively preventing the flow of current. This makes it an ideal material choice for electronic components and circuit boards that require insulation.
• Stability: The electrical insulation properties of the aluminium oxide layer remain highly stable under various environmental conditions, providing reliable insulation over an extended period.

What is the downside of anodized aluminum

1. Higher cost

The anodising process for aluminium is relatively complex, resulting in higher costs. The specific reasons include:

• Equipment and processes: Anodising aluminium requires specialised equipment, such as electrolytic tanks, direct current power supplies, and temperature control systems. The procurement and maintenance costs of this equipment are relatively high.
• Complex process: The anodising of aluminium involves multiple stages, including pre-treatment (such as cleaning and acid etching), anodising, and post-treatment (such as dyeing and sealing). Each step requires strict control and monitoring, increasing the complexity of the process and the operational costs.
• Energy consumption: The anodising process for aluminium requires a significant amount of electrical energy, particularly in large-scale production, resulting in substantial energy costs.

2. Increased brittleness

Although the aluminium oxide layer formed by anodising is hard, it is also relatively brittle and prone to cracking. Specific issues include:

• Brittle material: Aluminium oxide is inherently a brittle material, and when subjected to external impacts or drastic temperature changes, it is prone to cracking or chipping. This poses a disadvantage for components that need to withstand impacts or vibrations.
• Thickness impact: The thicker the anodised aluminium layer, the more pronounced the brittleness becomes. In some applications, it is necessary to strike a balance between hardness and brittleness to avoid fragility issues caused by an excessively thick oxide layer.

3. High processing conditions requirements

The anodising process for aluminium requires strict control of multiple parameters, which adds to the complexity and difficulty of the operation. For applications that require high-performance aluminium products, we have a modern large-scale factory equipped with the latest machinery and technology. Our facility features eight anodising tanks in two sizes, capable of processing metals in various colours. The tanks for silver, black, grey, and gold have dimensions of 7 x 1.5 x 1.5 metres, while the tanks for red, green, blue, and orange measure 1.5 x 1.5 x 1.5 metres. Together, these facilities provide a total processing area of 418.5 square metres.

We guarantee to provide high-quality services, tailored to your specific specifications and requirements for customised components. This enables us to handle projects of various scales while ensuring efficient production and timely delivery. We have established a stable and reliable supply chain network, collaborating with excellent material suppliers to ensure that we consistently deliver high-quality products and services. We have built a strong reputation in the anodising of aluminium processes. Conoco’s anodising process for aluminium is undoubtedly an ideal choice. Specific challenges include:

• Electrolyte concentration: The concentration of the electrolyte directly affects the quality of the oxide layer formation. Concentrations that are either too high or too low can lead to unsatisfactory anodising results, necessitating precise formulation and regular monitoring.
• Current density: Controlling the current density is crucial for the uniformity and quality of the oxide layer. A current density that is too high may result in excessive oxidation, while a density that is too low can lead to an uneven or incomplete oxide layer.
• Temperature control: Fluctuations in temperature during the anodising process can affect the quality of the oxide layer. A precise temperature control system is required to maintain the stability of the electrolyte temperature.
• Time management: The duration of the anodising process needs to be adjusted according to specific requirements, as durations that are too long or too short can affect the performance of the oxide layer.

How long does anodized aluminum last?

The expected lifespan of anodised aluminium depends on several factors, including the usage environment, the thickness of the oxide layer, post-treatment methods, and regular maintenance. The following are some of the main factors that influence the expected lifespan of anodised aluminium:

Factors affecting the expected lifespan of anodised aluminium

1. Usage environment: In dry, indoor conditions, the lifespan of anodised aluminium can extend for several decades. In harsh environments with humidity, salt spray, or acidic and alkaline conditions, the lifespan of anodised aluminium may be shortened, but it typically still maintains good corrosion resistance and aesthetic appeal.
2. Oxide layer thickness: A thicker oxide layer provides better corrosion resistance and wear resistance, thereby extending the lifespan. Typically, the thickness of anodised layers in industrial standards ranges from 5 to 25 microns, while special applications may require thicker oxide layers.
3. Post-treatment methods: Sealing treatments (such as hot water sealing or chemical sealing) can significantly enhance the corrosion resistance and lifespan of the oxide layer. Sealing after dyeing can also improve the colour stability.
4. Regular maintenance: Periodic cleaning and upkeep can extend the lifespan of anodised aluminium by preventing the accumulation of contaminants and corrosion.

Typical expected lifespan

• Indoor applications: In indoor applications, the expected lifespan of anodised aluminium is typically over 20 years. For example, anodised aluminium window frames, door frames, and household appliance casings can remain in good condition for decades under normal usage and maintenance conditions.
• Outdoor applications: In more moderate outdoor environments, such as typical urban settings, the expected lifespan of anodised aluminium can also reach 10 to 20 years. If the anodised layer has undergone thorough sealing treatment, this lifespan can be further extended.
• Harsh environments: In highly corrosive environments, such as marine settings or industrial chemical environments, the lifespan of anodised aluminium may be reduced to 5 to 10 years, but it can still provide adequate protection.

Measures to extend the lifespan of anodised aluminium

1. Choose the appropriate anodising process: Select the suitable anodising process and oxide layer thickness based on the usage environment to maximise durability.
2. Perform sealing treatment: Conduct effective sealing treatment after anodising to prevent the pores in the oxide layer from absorbing contaminants and corrosive substances.
3. Regular cleaning: Maintain the cleanliness of the anodised aluminium surface to prevent the accumulation of dust, salts, and chemicals.
4. Avoid mechanical damage: Take care to avoid scratches and impacts on the anodised aluminium surface, as such damage can compromise the protective layer and reduce corrosion resistance.

Applications of anodised aluminium

• Architecture and decoration

Anodised aluminium is very common in the fields of architecture and decoration. It is often used for building curtain walls, door and window frames, exterior wall decorations, railings, and handrails.

• Automotive industry

In automobile manufacturing, anodised aluminium is widely used for body panels, wheels, engine components, and interior trim. Anodising not only enhances the corrosion resistance and wear resistance of aluminium but also improves its appearance, increasing the aesthetic appeal of the products.

• Household and consumer goods

Anodised aluminium is commonly used in cookware, lighting fixtures, sports equipment, and home decor items. Its corrosion resistance, wear resistance, and aesthetic qualities make these products more attractive and functional.

• Industrial equipment

In industrial equipment, anodised aluminium is applied to various mechanical components, storage tanks, piping, and drive systems. Anodising enhances the wear resistance, corrosion resistance, and hardness of the material, thereby extending the lifespan of the equipment.

Summary:

Anodising aluminium is an effective process that significantly enhances the corrosion resistance, hardness, and aesthetic appeal of aluminium products. Although the anodising process is complex and relatively costly, its excellent performance has led to widespread application in various industrial sectors. We base our operations on meeting customer expectations and values, continually strengthening production planning management, optimising production processes, enhancing supply chain collaboration, controlling production costs, and improving employee skills. We strive for continuous improvement and excellence while consistently increasing customer satisfaction.