There is a wide range of aluminum anodizing colors to choose from; therefore, product developers need to know how to color match before releasing the end product. Let’s examine more on anodizing aluminum parts, how to color anodized aluminum and the common anodized aluminum colors.
What is Aluminum Anodizing?
Anodizing is an electrolytic process that produces excellent mechanical properties to enhance aluminum parts' durability and visual appeal. Manufacturers use the anodizing process for corrosion resistance to prevent surface scratches and improve surface hardness, making it an ideal foundation for painting or coating.
The aluminum parts are coated using a wear-resistant oxide layer which meets the aesthetic requirement of most users.
What are The Types of Anodizing Processes?
Manufacturers use three common types of anodizing processes, Type 1, Type 2, and Type 3. Each method differs due to the coating intensity.
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Type 1
This anodizing process is a “lighter” alternative. It uses chromic acid as the electrolyte. During the electrochemical process, the positive particles from the aluminum part form microscopic grooves, which are oxidized to form an oxide layer. Aluminum parts made via this process have better corrosion and heat resistance.
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Type 2
This is the most common method of anodizing aluminum parts. Instead of chromic acid, this process uses sulfuric acid, which is more potent and produces better positive aluminum particles than Type 1. The oxide layer becomes thicker; therefore, the parts have better paint retention properties.
The common color options for this process include blue, red, brown, purple, green, gold, black, and grey.
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Type 3
Type 3 is the ideal one for hard coating and making heavy aluminum products. It uses a higher voltage and sulfuric acid.
How to Color Aluminum Parts Using Anodizing
The anodizing aluminum colors are very different from the ones used in powder coating or painting. The colors will depend on the grade, size, and finish tapes. Here's the process.
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Cleaning and Etching
The anodizing process begins with cleaning the aluminum part with detergent and rinsing tanks. The part is then etched to give a matte, polished and shiny surface finish. The etching and brightening are done to remove any trace amounts of metal. The material removed depends on the size, shape, temperature, and solution pH.
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Build the Film Layer
After cleaning, you need to build the oxide layer on the aluminum part. Depending on the coating intensity you want to achieve, you can use Type 1, 2, or 3 anodizing processes. Once the piece is suspended in the electrolyte, you need to keep in mind that the shape and size of pores depend on the metal alloy.
In addition, the depth of the pores will depend on the electric voltage, tank temperature, time in the tank, and solution concentration.
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Adding the Color
Manufacturers add anodized aluminum colors in four ways, dip coloring, electrolytic coloring, interference, and integral coloring.
With dip coloring, the part is placed in a tank containing a dye. Once the dye is absorbed into the pores, the surface is boiled in de-ionized water to stop further reactions. Although there are many coloring variants, they are not UV resistant.
On the other hand, with electrolytic, the part is immersed in a solution containing metallic salts. These salts fill the pores to form a UV-resistant layer. However, the colors are limited to brown and black.
Interference coloring works by enlarging the pore structure. The metals are then deposited, which results in blue, green, and yellow to red colors. These colors form because of optical interference effects. Integral coloring combines coloring and anodizing by adding bronze and black shades.
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Sealing Off
Once the aluminum part is completely dyed, the last step is sealing it off to preserve the color. This sealing process protects the part from absorbing undesired molecules.
How Do You Color Match With the Aluminum Parts
There are several possible colors for anodizing aluminum. For effective results, the product developer needs to understand the concept of color matching. Let’s take a look at some of the critical factors you should look out for when matching colors.
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The Finish Type
To achieve the best aluminum reflective properties, the part of the film is essential. Use a sample with the same finish when color matching.
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The Aluminum Grade
When anodizing aluminum parts, looks out for the grade. Each aluminum grade has a different color variant and shade, which could affect the color matching.
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The Part’s Crystalline Structure
The crystalline structure affects the reflective properties of the aluminum part. Therefore, before you color match, check that the reflective angle is the correct one.
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The Number of Dyes Used
The dyes affect the color variation. When product developers use more dyes, there’s an increase in color variation. During layering, this variation also differs.
Benefits of Anodizing Aluminum Parts
If you anodize your parts, here are some advantages.
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Aesthetic Value
Anodized aluminum parts have a visually appealing look. This makes them popular with users because they are market-ready.
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Corrosion Resistance
The oxide layer from the anodizing process protects the aluminum parts from corrosion. This makes them durable than other parts which have had powder coating or painting.
Summary
After manufacturing is done, it’s essential to have a quality surface finish. There are different anodizing processes that product developers can use. It’s also vital to choose the best anodizing aluminum colors according to the aluminum part. This makes it easier to color match and get the best end product.
Anodizing has benefits such as boosting the product's aesthetic value, enhancing the surface finish, and increasing durability. Therefore, it's an essential step in manufacturing aluminum parts for any industry.
