Anodizing Dyes Explained: Everything you Need to Know

Anodizing dyes are special dyes used to color anodized metals. The layer of anodized dye improves the base metal's wear resistance and provides a fade-resistant coating. Organic anodizing dyes are generally used as they are eco-friendly and offer a broad spectrum of colors.

This article discusses anodizing dye, its types, benefits, and applications, and compares it with anodizing paints.

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What is an Anodizing Dye?

Anodizing dyes are color pigments, either in the form of powder or liquid, that develop a permanent color to the anodized layer.

Dyes used in anodizing are composed of metal salts which provide the required colorfastness and hue.

Each type of dye is composed of different combinations of chemical compounds, such as chromium, iron, nickel, and cobalt.

The chemical structure of each anodizing dye is unique, and thus, a variety of color shades can be achieved.

The most commonly available anodizing dyes are organic and inorganic metal salt dyes.

Anodizing develops a porous oxide layer on the aluminum surface, making it suitable for absorbing dyes.

Though anodizing is performed on non-ferrous materials like aluminum, magnesium, and titanium, aluminum is ideally chosen as it is lightweight and abundantly available.

Adding color to an anodized part is an add-on process that enhances the aesthetics by yielding rich, vibrant colors.

Anodizing is also performed without a dye and is known as clear anodizing.

Aluminum parts are color-anodized using immersion and Two-step electrolytic coloring techniques. The most commonly used DIY method is the immersion process.

Adding distilled water, you can make dye in a powder or liquid concentrate form ready for use.

After you anodize a part, dip it into the dye solution to get the desired color.

The time the part is left in the dye, and the dye concentration depends on the hue you want to achieve.

To make the color last longer, put the part in a hot ionized bath - this process is called sealing.

Sealing closes up the openings in the oxide layer, which prevents fading of colors and helps the colors stay in place.

Types of Anodizing Dyes

A wide range of anodizing dyes is available to bring an excellent finish to aluminum parts.

Two commonly used dyes are organic and inorganic dyes.

Organic Dyes

Organic dyes have a chemical structure that is free from heavy metals. Thereby having a positive impact on the environment.

Organic dyes are used on anodized parts with a minimum of 20μm anodic film thickness for a good gloss coat.

Though sensitive to alkaline conditions, these coatings are rigid and offer more stability than surface coatings, like paint, powder coating, etc.

Organic dyes are non-toxic, easily disposable, and support sustainable living.

These dyes are not colorfast, especially when exposed to high UV conditions.

Inorganic Dyes

Inorganic metallic dyes are a popular choice for two-step electrolytic coloring. They are made of iron and manganese oxides.

However, the colors you can achieve with these dyes are limited to brown, bronze, and black shades.

In addition, these dyes are more fade-resistant and can withstand UV exposure better than organic dyes.

To ensure the dye doesn't leach, the pH level of the sealer bath should be at least 5.3.

Factors to consider when color anodizing using a dye

The factors to be considered when color anodizing using a dye are as follows:

Anodizing voltage and time

To determine the color of a part, you need to decide the voltage and the length of time for the anodizing process.

Increasing the voltage or anodizing time will make the oxide layer thicker, allowing for more color absorption.

Type of Dye Used

The longevity and brightness of the coating depend on the type of dye used, either organic or inorganic.

You should consider the environment in which the part will be exposed when deciding which dye to use.

Inorganic dyes are best for parts exposed to alkaline conditions or high levels of UV radiation.

Dye Concentration

The amount of dye you use will affect the color you get. The more dye you use, the brighter and more intense the color.

Dyeing time

The time duration that you immerse the metal components in the dye solution also affects the intensity of the color.

You should immerse the components longer if you want vibrant and dark shades. This way, you can select the desired hue for a particular component.

Sealing

Sealing the part soon after anodizing is important to prevent the color from leaching out.

You can make the color last longer and reduce maintenance by properly rinsing and sealing the part.

Benefits of using anodizing dye

Fade-resistant

Anodizing dye gives your anodized aluminum parts a permanent and attractive finish.

The dye is sealed and deeply penetrated the porous oxide layer, making the coating fade-resistant and durable.

This makes color anodizing suitable for architectural parts exposed to different weather conditions.

Increased wear resistance

The anodizing process creates an extra layer of oxide on the surface, which absorbs the dye, making it more resilient to scratches and impacts.

This makes anodizing dye an ideal choice for making sports equipment and car parts, giving them increased wear resistance.

Durable

Anodizing dyes offer durable coats that are chemically stable and won't degrade over time.

This means you won't need to invest much time and money in maintaining parts.

Also, these coats can help improve the part's operating conditions and life span.

Multi-coloring

Anodizing dyes allows you to create colorful parts easily. You can experiment with different color combinations, like adding a dark color over a light-colored base.

Also, the uniform coat created by anodizing eliminates defects such as peeling, so you don't have to worry about fading colors.

Applications 

Anodizing dyes have been used to color aluminum and other non-ferrous metals for a long time.

Various color anodized parts like railings, window frames, and doors are used for high-end architecture.

Gold anodizing is common across many fields, such as dentistry, medicine, and electronics.

Red, yellow, and black anodizing dyes are used to color safety and road signs, making them durable in tough outdoor conditions.

Black anodizing dye increases the lifespan and heat absorption of hard anodized cookware. Light-colored anodizing dyes help to improve the reflectivity of aluminum roofing.

Best Anodizing Dyes

Commercially, many enterprises offer anodizing dyes. Following are a few brands that supply different shades of anodizing dyes.

Interactivia Anodizing Dye

Interactivia offers a selection of anodizing dyes in powder form.

When you mix the powder with distilled water, it creates a dye bath. Each 80 ml bottle of powder makes up to 7.6 liters of dye.

The shelf life of this product is between 5 and 10 years.

Caswell Anodizing Dye

Caswell offers a variety of colors for anodizing dyes, including deep red, bronze, and copper.

You can get 4.8 ounces of the dye in powder form, which should be diluted in 2 gallons of water.

To get the desired color, submerge your components in the dye solution for 15 minutes.

All the dyes meet ROHS compliance, so you can be sure they don't contain any banned substances.

Anodizing Dye vs Anodizing Paint

Parameters	Anodizing Dye	Anodizing Paint
Composition	Water-soluble, organic pigments	Water-insoluble, inorganic pigments
Application	Immersion method	Spraying or Brushing
Color absorption	Deep penetration	Surface coating
Base coat	Not required	Requires a chrome or silver base coat
Characteristic	Long-lasting, fade resistance	Chances of peeling or chipping of the paint coat

Composition

The main difference between anodizing dye and anodizing paint is the ingredients they are made of.

Anodizing dye is made of water-soluble organic pigments that dissolve in water and are safe for the environment.

On the other hand, anodizing paints contain inorganic pigments in a resin-based binder and have volatile organic compounds, which can be harmful.

Application

Anodizing dye and anodizing paint are applied to parts in different ways.

Anodizing dyes are water soluble and can be absorbed into the porous structure of the metal's anodized film through immersion.

Anodizing paints, however, are applied by spraying or brushing, forming only a thin coat on the metal surface.

This type of coloring is applied to the metal's bare surface instead of the anodized layer, and the coating thickness can be increased depending on your needs by applying multiple coats.

Color absorption

The anodized layer has tiny holes, which can absorb the color pigments of an anodizing dye.

Anodizing dyes are water-soluble and can penetrate deeply into the metal surface.

Anodizing paints stick to the metal, making an outer coat.

The color pigments in anodizing paints are held in a binder, so they can't get into the holes. Instead, they make a thin layer over the metal.

Base coat

The porous nature of the anodizing layer allows the anodizing dye to penetrate through.

This improves the functionality and usage of an anodized part, providing excellent corrosion resistance and enhancing its aesthetics.

Anodized paint provides an anodized finish to metal parts that are not anodized.

It is best to use these paints over silver or chrome coats to obtain such a finish. However, this doesn't provide the same properties as a color-anodized part.

Characteristic

Anodized dye ensures that the components it colors are durable and won't fade quickly due to its ability to penetrate the porous oxide layer.

The durability of the anodized paint depends on the layers of paint and the conditions in which the components are used.

However, using anodized paint increases the risk of peeling and scraping.

Final Thoughts

When choosing a dye for anodizing, consider its ease of use and light or heat fastness.

Organic dyes are preferred over inorganic dyes because they offer a broad spectrum of color choices and are eco-friendly.

When preparing the dye solution, keep the pH between 5.5 - 5.8.

The pH of the dye bath indicates its solubility. Therefore, a lower pH value indicates lower solubility.

Frequently Asked Questions

Can anodizing dyes be mixed?

Yes, anodizing dyes can be mixed to get a completely different color, or subsequent dipping of different colors also render the same purpose. Either way, anodizing dyes offer the unique property of forming a uniform coat.

Can anodized aluminum parts be revamped?

Yes, anodized aluminum parts can be revamped by etching, thereby forming a dull finish. Though etching results in small dimensional differences, it does not affect the base metal.

Why is it difficult to get a consistent color among different batches of the anodized parts?

The anodized coatings transmit the light to the base metal, which is later reflected through the film. The difficulty in color matching arises due to the anodic film acting as a filter.