Hard Coat Anodizing: Tudo o que precisa de saber

Surface treatments are very crucial for the components manufactured. It not only helps with improving the smoothness of the components but also equips them with enhanced properties.

Anodizing is used for aluminum, and choosing hard coat anodizing can offer to enhance the aluminum properties in a seamless way. If you are also looking to learn about hard coat anodized components, read the guide below.

What is Hard Coat Anodizing (Type III)?

Anodizing is a process that is conducted electrochemically, creating layers of anodic oxide on the components. Most of the time, aluminum is anodized using hard coat anodizing. It adds more durability to the components and makes them suitable for use in different industries and applications.

Hard anodizing is composed of a dense coating that is created using aluminum oxide through the process of electrolysis. The process of hard anodizing makes the aluminum component coated with anodic oxide, creating a thick bond.

Hard anodizing makes the component equipped with electrical insulation, corrosion resistance, and surface hardness.

Material Used in Hardcoat Anodizing

The process of hard anodizing is conducted using various materials, but the two basic ones are as follows:

Electrolyte Tank: It is a tank in which the process of anodizing takes place; this tank is acid-resistant and has an acidic electrolyte solution.

Cathode: Cathode is made using lead or graphite sheets.

Hard Coat Anodizing of Aluminum Process

The process of hard coat anodizing of aluminum has different steps, and these are discussed below.

Pre-Treatment

The aluminum components on which anodizing has to be applied are first treated so that any impurities on the surface can be cleaned. It enhances the quality of the overall anodizing process. It even helps to clean the part of the aluminum, which is etched with acid, and creates a uniform surface.

Hard Anodizing the Metal

The component of aluminum is submerged in a solution present in the electrolyte tank. The tank has sulfuric acid in most cases, and the component is connected to the positive electrode, which works like an anode. The unreactive substance in the electrolyte tank is also placed, and it works like a cathode.

The pass of current in the solution in the tanks leads to the process of anodizing. The air bubbles move in the solution, and it cools down the sulfuric acid, which creates oxygen that allows hard coating foam to form on the component. An oxide layer is created on an aluminum surface.

The process of hard coat anodizing requires a high voltage of around 120V layer of oxide thickness, as there is an increase in the resistance to current. It impacts the deposition process and hence requires a raise in voltage. To control the layer thickness, factors like acid content, time period of the process, and temperature of the electricity can be controlled.

Post-Treatment

After the required layer of thickness is achieved, the component is removed from the electrolyte solution. It is then rinsed and sealed to make it corrosion-resistant. Some post-treatment processes, like dyeing and application of lubricating film, are also conducted.

Pros of Hardcoat Aluminum Anodizing

Hard coat aluminum anodizing has various benefits, and some of these are as follows:

• Hard coat anodizing creates a hard surface on the aluminum component, which makes it resistant to scratches and wear.
• The corrosion resistance improves as aluminum has an oxide layer. The aluminum component has a protective layer that protects the aluminum from chemicals, oxidation, moisture, etc.
• The durability and lifespan of the aluminum component increase when the hard coat anodizing is applied to the aluminum component. The layer of thickness can make the component withstand harsh conditions.
• The layer of anodizing makes the components wear-resistant as the surface hardness of metals is increased. These coatings make the component resistant to wear and abrasion.
• Anodized aluminum has seamless electrical insulation, which makes it electrically conductive.

Hard Coat vs. Regular Anodize of Aluminum

Hard coat anodizing and regular anodizing differ in various ways, and some of these differences are as follows:

Thickness

Hard coat anodizing forms a thicker layer than regular anodizing. Thus, the thickness of the surface makes aluminum durable.

Seal

Hard anodized aluminum is not sealed as it has a thicker surface. This makes the aluminum component durable.

Meanwhile, in regular anodizing, the aluminum has to go through the process of sealing, which protects the component against corrosion. It is less durable and hence can wear out quickly compared to hard-coat anodized aluminum.

Resistência à corrosão

The layer of oxide is hard and thick in the hard coat anodizing; it offers excellent corrosion resistance, creating a protective barrier. The component can withstand chemical and environmental exposure. Whereas regular anodizing also offers corrosion resistance, but is not as good as hard coat anodizing,

Hardness and Wear Resistance

Hard coat anodizing, as the name suggests, creates a hard layer of coating, making it more wear-resistant. Whereas in regular anodizing, the coating is not very hard, and hence the component lacks wear resistance compared to hard coat anodizing.

Appearance

The appearance of the hard anodizing varies based on the nature of the aluminum. Some of them create a black and darker gray color, whereas some are towards a blend of bronze and gray.

Considerações sobre os custos

Hard coat anodizing is expensive compared to regular one as the process takes longer and consumes more electricity to create a thick layer.

Standard Specifications of Hard Coat Anodize

The standards applicable to hard coat anodizing are as follows:

• AMS 2482 (PTFE Sealed)
• AMS 2469
• MIL-A-8625 Type III
• ASTM B580 Type A
• ISO 10074
• MIL-A-63576 (PTFE Sealed)

Applications for Hard Coat Anodizing

Hard coat anodizing is used in various applications and in different industries, and some of these are as follows:

Indústria automóvel

No automobile industry, hard coat anodizing enhances the performance of the components. It is used for engine blocks, suspension parts, and pistons. The components have a layer of protection against chemicals, wear, and heat, which improves their durability.

Indústria aeroespacial

The aerospace industry uses hard anodizing to enhance the wear resistance and hardness of aluminum parts. Components like engine parts and landing gear of aircraft require hard anodizing.

Defense Industry

Hard anodizing is used in the defense industry to improve corrosion resistance and durability in different parts of applications. Components like pistol frames, rifle receivers, and other parts of firearms are made using hard anodized coating.

Indústria eletrónica

Electronic devices require protection against environmental impact. The coating helps to keep the component working for a longer span. It creates a hard surface on connectors, heat sinks, and electrical enclosures.

Factors Affecting Hardcoat Anodizing Quality

The quality of hard coat anodizing can be affected by various factors, which are as follows:

• The composition of the alloy has a tendency to impact the hard coat anodizing quality, as every alloy reacts differently to it.
• Surface preparation before the hard coat anodizing is also crucial. If the process of pre-cleaning is not conducted properly, there is a chance that the quality of hard coat anodizing is impacted.
• In most cases, the anodized components are sealed after the anodizing process. If the components are not properly sealed, it may impact the quality of the anodizing.
• The skills of operators play a vital role in the anodizing quality, a highly skilled operator will always conduct the process in an adequate way.

Conclusão

Understanding the process of hard anodizing is very important so that you can always achieve optimal results. When it comes to having hands-on components equipped with hard coat anodizing, you can get in touch with us at DEK. We offer high-quality aluminum components that are manufactured using a hard coat and anodizing as a surface finish.

FAQs

What seals can be used for aluminum hard coats?

Seals like PTFE, nickel fluoride, and sodium dichromate are used for aluminum hard coating.

How long will hard anodized aluminum last?

Hard anodized aluminum is highly durable and may last for decades.

How to get maximum adhesion on aluminum hard coat？

To get maximum adhesion, dichromate and unsealed hard coats are chosen.

What is the coating thickness for aluminum hard coats?

The coating thickness of aluminum hard coats can range up to 120 micrometers.