Revestimentos de alumínio: anodização vs. revestimento em pó vs. pintura

Aluminum Coatings: Anodizing vs. powder coating vs. painting

Aluminum Coatings Feature Image

Aluminum alloys are among the most used metals in the world. I'm not talking about ore deposits here, but about the use of aluminum in all areas of human life. Aluminum is light, durable and strong. It is also corrosion resistant because its thin oxide layer only melts at over a thousand degrees Celsius. However, aluminum coatings are often used, the most common being painting, oxidation and powder coating.

Why coat aluminum?

This is a legitimate question because aluminum has its own protective layer against aggressive environmental conditions. So why coat it?

Modern manufacturers and customers demand much more from aluminum parts, and the conditions these parts must withstand can be overwhelming, even for the protective oxide layer.

For example, rocket covers are made of thin aluminum sheets and the temperatures they have to withstand approach the melting point of the oxide layer. Although this point is not taught, the film can crack easily due to rapid temperature fluctuations. The ship's parts are immersed in highly corrosive salt water, which causes even the aluminum to gradually corrode. Modern industry presents us with new challenges when it comes to corrosion and the answer manufacturers have found is aluminum cladding.

A brief overview of anodizing, powder coating and painting

Before we start comparing the three most commonly used aluminum coatings, we wanted to refresh your memory on these techniques in case you're a bit lost on the details.

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Anodizing

Anodizing is a unique process. No new materials are added to create a coating, but the material itself is used. A piece of aluminum is placed in a container with conductive liquid. A low-voltage, high-current current flows through the container and part. This causes the oxide layer to become thicker and more porous on its outer surface.

Liquid paint

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This is the oldest conventional technique for coating virtually all materials. You buy a can of paint and a brush and that's it. Just be careful not to breathe out too much paint, as it is somewhat toxic until it solidifies. Over the years, a huge variety of available colors have appeared on the market. And you can also mix some colors to get the shade you want.

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Aluminum Powder Coating Process

Powder coated aluminum is the new eco-friendly method of applying paint. You need professional equipment, that is, a compressed air gun that sprays ionized dry powder particles that adhere to the surface of the aluminum part due to ionization. Then you place the piece in the oven, heat it and the film of dust becomes uniform and adheres to both the powder and the piece.

Powder Coating vs. Powder Coating wet painting

First, let's compare the two similar methods. Both can be considered paints, but they are very different, as are their respective areas of application.

If you are on a budget, wet painting is your best choice. The reason is: you don't need any equipment, just a brush and paint. This makes them perfect for producing small quantities. Another advantage of budget paint is that you can apply a thick coat of it to a poor surface finish and the surface will be smooth.

Other than that, liquid paint is great for its variety of colors. Powder coatings cannot offer as many different shades as you can get commercially and by mixing different colors.

Powder differs from liquid paint in several ways. Firstly, it is not poisonous. However, one problem with powder coating is that you still need to wear protective clothing because inhaling small particles of powdered paint is not good for your lungs.

Powder coatings are more uniform and less prone to cracking because the powder particles sinter with the base material. Liquid paint can cause stains and an uneven surface layer.

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Anodizing vs. powder coating

In fact, it is not entirely accurate to compare anodizing and powder coating. The reason for this is that these two processes can complement each other. After anodizing, the aluminum surface becomes more porous. You can tell if the piece looks milky rather than having a shiny metallic finish. These pores are ideal for powder particles to flow through as they are melted.

Both anodized aluminum colors and powder colors are the same type.

Both techniques create a protective layer against corrosion and wear. However, the anodizing result is much more durable because the coating is part of the material.

Anodizing vs. liquid paint

When painting, the pores created by anodized aluminum films are not as useful for surface finishing as powder coatings. Anodized aluminum finishes are much inferior compared to painted ones, but if you need a matte texture, there's nothing better.

Unlike painting, anodizing is not as toxic, but it requires a lot of energy and additional equipment, so painting is obviously cheaper.

Most paints conduct electricity, but porous anodizing reduces the part's conductivity. You need to take this into consideration when using aluminum parts for electrical appliances.

Conclusions

Wet painting, powder coating and anodizing are important protective processes for aluminum parts. All of them are good for corrosion resistance, and painting and powder coating improve the aesthetic appearance of the part and its surface finish. Anodizing only works in conjunction with powder coating. Basically, if your budget is as big as possible, you should use anodizing and powder coating for maximum protection and even some wear resistance. Painting is great if you want to get a truly original color or if you're just starting out and don't have a lot of money for expensive equipment or if your lot is too small to invest. Just don't forget your protective gear, otherwise you could end up with a severe headache or even worse discomfort. The same applies to powder coating. You don't want to inhale the dust.

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