Different Types of Anodizing Techniques


Aluminium is everywhere these days, isn’t it? From the sleek frame of your car to medical equipment and even an aircraft, you can find it in different industries. All thanks to its strength and conductivity. However, due to its highly reactive nature, it could end up being weak, which is why metal finishing techniques like Anodizing are used.

This process not only enhances Aluminum’s corrosion resistance but also makes it durable in challenging environments.

In this article, we are going to discuss all about Andozing and its types in detail.

Let’s get started!

What is Anodizing?

Anodizing is a surface treatment process applied to metals, primarily aluminium that involves creating a controlled oxide layer on the metal’s surface through an electrochemical reaction. This oxide layer provides enhanced corrosion resistance and improved durability, and it can be customized to achieve various colours and finishes.

Aluminium Anodizing is widely used to enhance the performance and aesthetics of metal parts and components in industries such as:

  • Aerospace
  • Automotive
  • Construction
  • Electronics

Types of Anodizing

It’s time to understand different types of Anodizing techniques that could be useful for various applications; let us discuss these types one by one:

Chromic Acid Anodizing (Type I):

Now, let’s take a closer look at Chromic Acid Anodizing (Type I). This process involves immersing aluminium parts in a solution of chromic acid and water, creating a chemical dance that results in the formation of a thin, dense, and highly corrosion-resistant oxide layer on the surface of the metal.


The oxide layer produced by chromic acid anodizing is very thin, typically around 0.00002 to 0.0001 inches (0.5 to 2.5 microns) thick. Given the thinner coating layer of Type I, it absorbs less colour during dyeing, resulting in a greyish hue.

A red color anodized aluminum parts texture design. CNC parts.

This characteristic restricts the decorative use of chromic acid anodizing. Nonetheless, it remains feasible to dye Type I coatings black, serving as a protective layer for optical component housings.


Type I anodizing is commonly used in the aerospace industry for components such as aircraft structures, engine parts, and fasteners. It provides a protective coating that meets stringent industry standards while maintaining the lightweight properties of aluminium.

Sulfuric Acid Anodizing (Type II):

Sulfuric acid anodizing, also known as Type II anodizing, involves immersing aluminium parts in a sulfuric acid electrolyte solution. A direct current is passed through the solution, causing an oxide layer to form on the aluminium surface. The thickness of the oxide layer can be controlled by adjusting factors such as voltage, time, and temperature.


Type II anodizing typically produces oxide layers ranging from 0.0002 to .001 inches thick. This oxide layer enhances corrosion resistance, improves surface hardness, and provides a base for colouring or further surface treatments.


The process can be tailored to achieve specific properties based on the application requirements.


Type II anodizing is widely used in various industries for decorative, functional, and protective purposes. It finds applications in architectural components, consumer goods, automotive parts, and electronic enclosures, where corrosion resistance, durability, and aesthetic appeal are important. The colour options available for this type of anodizing are black, gold, grey, brown, red, blue, and green.

Hard Anodizing (Type III):

Hard anodizing or Type III anodizing, or hard coat anodizing, is an electrochemical process that produces a thick and dense oxide layer on the surface of aluminium. In the process, aluminium parts are immersed in a sulfuric acid electrolyte solution at lower temperatures and higher voltages than standard anodizing processes.


Type III anodizing produces oxide layers that are typically thicker than those produced by Type II anodizing, ranging from 0.0002 to .001 inches thick. The resulting oxide layer is exceptionally hard, wear-resistant, and provides superior corrosion protection compared to other types of anodizing. It also offers excellent electrical insulation properties.


As Type III anodized coatings can be made quite thick, they are very useful for refurbishing wear coating. Hard anodizing is also commonly used in applications requiring extreme durability, wear resistance, and dimensional stability.

Anodized parts

It finds applications in military, aerospace, automotive, and industrial sectors for components such as pistons, cylinders, gears, and hydraulic systems where reliable performance under harsh conditions is critical.

Choosing the Right Anodizing Type for Your Applications  

Now that you have an idea about the main types of anodizing, it’s important to understand that choosing the right kind of anodizing is crucial for cost-saving and avoiding any safety hazards down the line. Let’s talk about some key considerations for this:

Consider Application Requirements

Determine the specific requirements of your application, including factors such as corrosion resistance, wear resistance, aesthetics, and electrical conductivity. For example, in marine applications where parts are exposed to saltwater, corrosion resistance is crucial. Hard anodizing (Type III) is often preferred due to its superior corrosion resistance and durability.

Take into account the environmental conditions to which the parts will be exposed, such as exposure to moisture etc.

Assess Material Compatibility

Consider the type of substrate material (e.g., aluminium alloy) and its compatibility with different anodizing processes. Certain alloys may require specific types of anodizing to achieve optimal results.

Review Regulatory Compliance

Ensure that the chosen anodizing process complies with relevant regulatory standards and industry specifications, especially for applications in sectors such as aerospace, automotive, and medical.

Compare Cost and Lead Time


Evaluate the cost-effectiveness and lead time associated with each anodizing process, considering factors such as material, labour, equipment, and turnaround time.

Consult with Anodizing Experts

Seek advice from experienced anodizing professionals or service providers like Dainsta, who can offer insights and recommendations based on their expertise and industry knowledge.

Parting Thoughts

In this article, we’ve discussed anodizing, exploring its various types and their applications. From Chromic Acid Anodizing (Type I) to Sulfuric Acid Anodizing (Type II) and Hard Anodizing (Type III), each process offers unique advantages tailored to specific industrial needs. Choosing the appropriate anodizing process is not just a matter of preference; it’s a critical decision that impacts cost, performance, and safety. Whether it’s ensuring corrosion resistance in marine applications or enhancing durability in automotive components, selecting the right anodizing or metal finishing types is important.

Looking for Anodizing services for your Aluminium parts Let Dainsta get you started!

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