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Everything You Need to Know About Anodizing Aluminum

Anodizing is a great way to make a durable and aesthetic surface finish on your aluminum parts. There are some features you need to know before anodizing though.

Categorys:Prototype Finishing & Painting

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Posted on Agust, 27th, 2020 | By WayKen Rapid Manufacturing

Once you’ve finished with the functionality of your product, you will inevitably get to the point where finishing your parts is concerned. Painting seems to be the most obvious option but if your part is made of aluminum you have a different option: aluminum anodizing. Also, aluminum anodizing is a very durable post-processing technique.

How Do You Anodize Aluminum?

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So, what’s so different about anodizing aluminum compared to other finishes is its process. The majority of protective covers are added to the material while in anodization, the cover is formed by removing positive ions from the surface of aluminum parts. Anodizing is divided into three different types:

Type 1. The “light” type. You put the part into a tank with chromic acid and you make it the anode while the cathode is inserted into the acid as well and are positioned to surround the part. Then, the current passing through the acid makes the positive particles in aluminum leave its surface. They leave microscopic grooves in the surface that are almost instantly oxidized and covered by the oxide layer. It is very heat and corrosion resistant and is generally harder than the unoxidized aluminum.

Type 2. Sulfuric acid is more potent than chromic so the grooves and therefore the protective layer is thicker. The grooves actually become so deep they can be filled with a special kind of special paint.

Type 3. Hard anodizing. This type of coating is used for heavy wear parts working under high temperatures in corrosive aggressive environments. The general process is the same but the voltage is higher, the concentration of the sulfuric acid is higher. The resulting oxidized layer is about as thick as a human hair ( which is very thick in terms of coatings).

The Benefits of Anodizing Aluminum Parts

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Why should you consider anodizing aluminum rather than painting or another type of finish? There are actually a few points for that.

  1. The anodized layer is very hard. Oxides are usually harder than their base metal. The same thing can be said for aluminum dioxide. When we anodize a part, we increase the surface area of its oxide layer. So, The surface of the part becomes much harder. With Type 3 anodizing it can reach some metal cutting tool steels.
  2. The coating is very resistant to any kind of chemical reaction. The aluminum dioxide is extremely stable and doesn’t react with salts and the majority of other natural elements. Even at high temperatures, the oxide film perseveres.
  3. If you want to color your part and not be afraid that it peels off, you can anodize the part. The colorant stays deep inside the pores of the surface and it is impossible to chip or scratch unless you grind off the whole outer layer of the part.
  4. The process is extremely eco-friendly. The by-products are salts and the same remaining electrolyte. It makes anodizing stand out from toxic paints that are often used in the industry.
  5. Apart from paint, you can make adhesives fill the pores so anodized aluminum parts can be glued together.
  6. Anodization offers a beautiful unique finish that has a rich color and yet retains the original metallic shine.
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Despite all the advantages, aluminum anodizing has some downsides as well. Firstly, anodized aluminum alloys are not suitable for kitchenware because they conduct heat poorly. In some extreme cases, it can result in temperature cracks when such parts encounter heat. Secondly, the fatigue resistance of anodized parts is lower because fatigue cracks are prone to concentrate in the pores.

Difference Between Simple Aluminum And Anodized Aluminum

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The visual difference between a machined and an anodized surface is obvious. Anodized aluminum is matted compared to the shiny finish of the machined aluminum. It is rougher and looks more porous, which it is, basically. However, the part still has its metallic look even after painting, which makes anodizing such a lucrative option. Worn aluminum parts may have discrepancies in their surface where the oxide layer was damaged and restored itself later having contacted with oxygen, this is not seen in anodized parts since the protective layer is much thicker and can’t be damaged easily.

Where Anodized Aluminum Is Used

Anodization found a lot of uses in different industries. Basically, when you need to harden aluminum alloys and make them more durable, You will look toward aluminum anodizing.

Window panes. Modern windows are constructed from lightweight and corrosion-resistant aluminum alloys. If you anodize the panes, it will be much harder to bend them, making the window more airproof.

Handheld devices. A lot of handheld devices (such as phones, MP3 players, speakers, etc.)  must be strong because they are often dropped or we accidentally strike something with them, we scratch them on something ( like keys or furniture) and not only should they resist these damages, they must not be deformed too much. By constructing appliance enclosures from aluminum with an anodized finish not only do they become durable but light as well.

Is Anodizing Aluminum Expensive?

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Anodizing aluminum is not a complex process. You can even do it at home and sometimes you maybe can anodizing aluminum cost. You’ll need a tank that can withstand acids, a constant source of electrical current with high voltage and the cathodes usually brass or steel. However, you won’t get a surface quality of industrial grade. The layer will have a different thickness in different areas and so the finish will look different in certain areas.

For the best surface quality it is best you consider using anodizing aluminum services. They will have the best equipment and the quality will be much higher. In addition, if you have a batch of parts to be anodized, you can do it much faster by outsourcing rather than purchasing your own equipment. Professional anodizing tanks can process tens of parts simultaneously in the same tank. They are just connected to the current as one large anode.

For the best surface quality it is best you consider using anodizing aluminum services. They will have the best equipment and the quality will be much higher. In addition, if you have a batch of parts to be anodized, you can do it much faster by outsourcing rather than purchasing your own equipment. Professional anodizing tanks can process tens of parts simultaneously in the same tank. They are just connected to the current as one large anode.

To Anodize, Or Not to Be Anodized?

If you have any quotations or projects to review, please don't hesitate to contact us. Here, we can offer more cost-effective and practical advice on different surface finishing services that can help enhance your prototypes and parts.

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