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Alodine Finish: A Guide to Conversion Coatings for Precision Machined Parts

Views: 5     Author: Site Editor     Publish Time: 2023-03-06      Origin: Site

Alodine finish is an important step in the production process for precision machined parts, providing greater corrosion and wear protection and helping to enhance appearance.

Using a conversion coating process, this type of finish can serve as a key part of creating parts that meet the highest standards of quality.

From components used in automobiles to ultra-precise medical devices and aerospace technologies, this robust protective layer has become increasingly necessary to protect sensitive metals from harsh elements.

In this guide, Kaiao will explore how aluminum oxide finishes are applied and their benefits for precision mechanical parts.

Precision Machined Parts

What is Alodine?

Alodine is an important industrial process used to create a chromate conversion coating on metal.

When applied and cured properly, this chromium-based conversion coating protects the metal from corrosion, weather wear, and other harsh conditions.

More than just a protective finish, Alodine also provides a bonding foundation for further finishes such as painting or powder coating that require adhesion to the metal substrate being coated.

The chromate conversion process has been increasingly popular in aerospace manufacturing due to its combination of protective qualities and longevity.

How Does Alodine Finish Work?

If you need a metal to have more durability, you may want to consider using the Alodine finish.

This process works by having the interaction of chromium salt in an aqueous solution that is applied as a chemical bath.

Through this interaction, a chromate conversion coating forms on the surface of the metal, which is crucial for providing corrosion protection from harsh conditions, as well as increased lubricity and dyeing properties which can give it a unique look.

This finish also acts as a base for further finishes such as paint or powder coatings, making it valuable when your metal needs to look and hold up better.

What You Need to Know About Alodine Coating Types

Alodine coatings are usually applied to metal surfaces to provide corrosion protection and improved paint adhesion. If you're in the business of using these coatings, then it's important to understand the various types available.  

MIL-DTL-5541 Type 1

Type 1 is a chromate conversion coating that provides good corrosion resistance and forms a base for organic coating systems.

It is often used on aluminum alloys, magnesium alloys, and steel parts.

The coating is composed of hexavalent chromium, which can cause skin irritation if not handled correctly.

This type of alodine coating should be applied with caution due to its potential health hazards.

MIL-DTL-5541 Type 2

Type 2 is also a chromate conversion coating, but unlike Type 1, it does not contain any hexavalent chromium.

Instead, it is composed of trivalent chromium and other materials in order to create an environmentally friendly alternative to the more hazardous hexavalent chromium version.

This type of alodine coating can be used on aluminum alloys, titanium alloys, and steel parts without any health risks associated with handling it.

Main characteristics of Alodine finish

This section discusses the main characteristics of Alodine finish and why it might be the right choice for your products.

Thin Film Application

One of the biggest benefits of using an Alodine finish is that it creates a very thin film on the surface of your metal objects.

This allows for greater flexibility when it comes to product design since you won’t have to worry about adding any extra bulk or weight to your parts.

Additionally, this thin film helps protect against wear and tear more effectively than thicker coatings.

Application at Room Temperature

Applying an Alodine finish doesn’t require any special equipment or preparation.

It can be done quickly and easily at room temperature, meaning there’s no need for preheating or cooling down your pieces before applying the coating.

This makes it easy to use in mass production scenarios where time is of the essence.

Great Conductive Surface

An Alodine finish also provides great conductivity properties due to its low electrical resistance levels.

This means that you can use it on many different types of metals without worrying about potential electrical problems arising from poor conductivity.

Additionally, this low resistance level helps ensure that there will be no issues with shorting out when two components come into contact with one another after being coated with an Alodine finish.

Fast Application Process

Finally, applying an Alodine finish takes very little time compared to other coatings, which can take hours or even days depending on the size and complexity of the object in question.

This means that you can get your products ready quickly and efficiently without worrying about waiting too long for them to be finished and ready for sale or shipment.

Alodine vs. Anodizing

If you’re looking for a protective and decorative finish for your aluminum products, you may have encountered two popular options: alodining and anodizing.

But what’s the difference between them? Let’s break it down.


Alodine is a chemical conversion coating that helps protect aluminum from corrosion, pitting, oxidation, and other forms of deterioration caused by exposure to air or water.

It also provides a clean surface for painting and other finishes.  

Alodine is also known as “chemical film” or “iridite.”

The process involves dipping the aluminum in a chromic acid-based solution that creates an invisible chromate layer on its surface.

This layer acts as a barrier to prevent rusting, corrosion, and fading of paint colors over time.

Additionally, it can improve electrical conductivity when used on electrical components like circuit boards or wiring harnesses.


Anodizing is another type of finish applied to aluminum products to provide protection against oxidation and wear-and-tear.

Unlike Alodine, Anodizing requires electricity (hence its name) to create an oxide layer on the surface of the metal that acts as a protective barrier.

This extra layer is harder than paint alone, making it more resilient against scratches and dents over time.

Additionally, depending on the type of anodizing used, hardcoat or decorative.

It can also give aluminum surfaces a sleek look with various colors ranging from black to gold.  

Applications of Alodine finish

Alodine finish is a kind of conversion coating that is mainly used in aerospace to improve the corrosion resistance of aerospace parts.

It is primarily composed of chromium but can also have other compounds and additives.

Alodine finish gives aerospace parts an extra layer of protection from the natural elements, benefiting planes and other transportation machines as they travel through various types of weather and environments in the sky.

Not only does it provide aerospace parts with more durability and sturdiness, but it can also reduce costs by increasing part longevity.

The aerospace industry especially relies on Alodine finish and its protective properties to ensure the safety and success of flights.


Alodine finish is a great conversion coating for precision machined parts due to its fast application process and good conductive properties.

It can protect aluminum from corrosion, pitting, oxidation, and other forms of deterioration caused by exposure to air or water.

Additionally, it has low electrical resistance levels, which ensures there will be no issues with short circuits.

KAIAO can help with its comprehensive range of services, which includes applying chemical conversion coatings such as Alodine finish on machined parts.

Our qualified team of technicians has the knowledge and expertise to ensure your parts are finished perfectly, quickly, and with the highest quality.

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