Anodized aluminum can be painted using oil-based paint. Before painting, the part is thoroughly cleaned to make its porous oxide surface free from dirt or contaminants. Degreasing and using etching primer allows multiple layers of paint to be coated, improving the strength and durability of the anodized aluminum part.
This article discusses how to paint anodized aluminum parts including everything you need to keep in mind before starting the paint work.
What's in this article?
- Things to consider when painting anodized aluminum
- What kind of paint should you use on anodized aluminum?
- Painting over anodized aluminum: step-by-step process
- Painting vs powder coating
- Pros and cons of painting anodized aluminum
- Restoring anodized aluminum
- Final thoughts
- Frequently asked questions
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Painting Anodized Aluminum: Things to Consider
The process of anodizing develops an integral oxide layer on the aluminum surface. This porous oxide layer protects the base material (aluminum) from deterioration.
Typically, the anodizing process if followed by adding dyes to attain the desired color, such as green anodizing or black anodizing.
After adding the dye, the surface is sealed to close the pores.
However, if you plan to paint the workpiece after anodizing, it is advised to skip the dyeing and sealing steps and paint the workpiece directly after anodizing.
Painting on an anodized aluminum enables the paint to flow into the pores, forming a durable coat.
When painted, the color pigments get seated on the material. Such coatings have a high chance of peeling off from the surface.
Generally, most hobbyists prefer painting anodized aluminum over color anodizing as the painting job is inexpensive and less time-consuming than the color anodizing process.
Painting an anodized aluminum part is recommended only when you need to enhance or change the coat's color or prevent corrosion from occurring due to a dent on the part.
It is relatively easier to paint on a part that is not sealed. This is because sealing prevents the adhesion of the paint.
A thorough scrubbing using sandpaper is recommended if the anodized part is sealed.
Using etching primer and oil-based paints ensures proper adhesion of the new paint coat. It is best to apply a protective clear coat for the color to last long.
You can also opt for a clear powder coating to seal the surface and protect the anodized layer.
What Paint Should you use on Anodized Aluminum?
Most paints can be coated on an anodized aluminum part, but each gives different results. The commonly used paints are oil-based, enamel, or acrylic paints.
Oil-based paints are usually preferred over acrylic paints as they are easy to paint, durable, and exhibit good resistance to corrosion.
For best results, three coats of matt finish paint are recommended. These types of paints take about two hours to dry completely.
Further, a clear protective coating will improve the part's overall appearance and make the paint last longer.
Spray painting on an anodized part makes painting more effortless, but this technique produces an uneven and poor surface finish on an anodized part.
It is best to manually paint an anodized aluminum part using a paintbrush rather than spray painting it.
Rust-Oleum has a series of sealant paints you can use to paint anodized aluminum.
You can follow the similar procedure to paint anodized titanium, steel, bronze, etc.
Painting Over Anodized Aluminum: Step-by-Step Process
Painting over anodized aluminum is a simple process. You'll need the following supplies to paint anodized aluminum.
|Dish liquid or soap|
|Clear protective coat|
Step 1: Cleaning
Preparing or cleaning the part is crucial before painting anodized aluminum.
Dirt or other contaminants can clog the porous structure of the anodized aluminum, preventing the paint coating from adhering to the surface.
Washing thoroughly in a soap-water solution followed by scrubbing using sandpaper or a wire brush will open up the pores, allowing the paint to seep in.
After cleaning the part thoroughly, allow it to dry.
Step 2: Applying Primer
Once the part is dried, apply a coat of etching primer to help the anodized surface absorb the paint properly, ensuring a durable coat.
Allow the part to be dried thoroughly before going to the next steps.
Step 3: Painting the anodized aluminum part
Once the primer has dried, you can apply a coat of paint to the anodized aluminum.
Oil-based paint can easily flow into the anodized part's porous structure, providing a better seal.
If required, you can apply multiple coats for a better finish.
Step 4: Applying a clear coat
Applying a clear coat or enamel sealer over the painted part is optional. This helps protect the paint from peeling off and enhances the anodized part's visual appeal.
Once dried, the part will be ready to use.
Painting vs Powder Coating: Which is best for Anodized Aluminum?
The porous structure of anodized aluminum makes it suitable for different topcoats.
The table below differentiates two basic top coating techniques: painting and powder coating.
|Equipment||Paintbrush||Specialized electrostatic spray guns|
|Coatings||Multiple layers||Produce a thick coat in a single operation|
|Durability||An additional layer of clear coat is applied for a lasting effect||Parts are cured in an oven which increases their durability|
The following factors will help you differentiate and adopt the best technique among painting and powder coating for anodized aluminum.
Part Preparation / Cleaning The Part
Painting an anodized aluminum requires you to prepare the part surface before applying a coat of primer. In powder coating, the process can be performed directly on the part.
Powder coating requires you to use special equipment, such as a spray gun, that can apply an electrostatic charge to the powder particles.
Also, you should have good experience with powder coating to achieve a uniform smooth coat on the anodized aluminum part.
Painting only requires a roller or flat brush, which you can easily do without much expertise.
Multiple coats are recommended while painting on an anodized part. This ensures that the paint lasts longer.
In contrast, the powder coating technique offers a thick coating in a single cycle.
Powder coating is generally durable and is often compared with anodizing as a cheaper and easy alternative to anodizing the part.
After painting an anodized part additional layer of protective clear coat is applied to enhance its durability.
In powder coating, the part is cured in an oven where the layers under high temperatures become resistant to abrasion.
For a DIY hobbyist to quickly apply color to anodized aluminum parts, painting is the best option over powder coating.
Pros and Cons of Painting Anodized Aluminum
|Improved appearance||The coat won't adhere well|
|Protects against further wear||It may damage the anodized layer|
|Customization of parts||Can trap moisture affecting its corrosion resistance|
Painting anodized aluminum allows you to customize it to blend in with other parts or give it a unique look.
The anodized surface is often sanded to provide better adhesion to paint. This can damage the anodized layer, striping off its protective properties.
Depending on the type of paint used, it may protect the anodized aluminum from further wear or degrade its corrosion resistance due to the moisture trapped during painting.
Painting an anodized aluminum is more accessible and pocket friendly. A beginner can efficiently perform this procedure.
The major limitation in taking up a painting project is the enormous effort needed in preparing the surface and repeating the procedure to get a durable coat.
Is it Hard to Restore Anodized Aluminum?
Often a question arises whether it is possible to restore or bring a fresh look to the oxidized or tarnished anodized aluminum parts.
The answer is Yes! By applying clear protective coatings, you can brighten up dulled anodized parts.
Apart from improving its overall appeal, these coatings improve the part's corrosion and wear resistance.
Metal cast anodized colors from Dupli-Color is a popular choice for such jobs.
The porous structure of the anodized aluminum allows it to absorb the colored pigments of paint.
However, you should be careful when preparing the material to remove any dirt or left-out coats of paint properly.
For better results, apply a coat of etching primer before painting. Also, oil-based paint will provide a better finish.
Frequently Asked Questions (FAQ)
Does painted anodized aluminum wear off?
Painted anodized aluminum parts are durable and long-lasting as the color pigments fill the porous structure of the anodized layer. Thus the chances of paint being worn out are minimal.
Can painted anodized aluminum be refurbished?
Yes, anodized aluminum can be refurbished. An extensive effort of scrubbing and cleaning will be needed to prepare the material for a new coat of paint.
How to clean painted anodized aluminum?
You can clean painted anodized aluminum with alcohol or acetone and organic solvents. Acetone offers an excellent cleaning agent and prevents color fade from the anodized part.
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