When making metal parts, it's essential to consider how the surface will look. Metal finishes make the part look better and can help improve its overall performance by making it more resistant to corrosion and wear. A common way to finish metal surfaces like aluminum, titanium, and many other metals is anodizing.
In this article, we'll talk about how anodization works, its benefits, how it is done, and its application.
What Is Anodizing?
Anodizing is a process that turns the natural oxide layer on metal's surface into an anodic oxide film. This extra thickness protects the part's surface and makes it look better.
Most anodized metals are aluminum and titanium, but other nonferrous metals can also go through the process. MIL-A-8625, which is a standard for anodizing, says that there are three different kinds of anodizing:
● Type I: Produces a very thin layer of oxide using chromic acid. It puts a thin layer on the surface of metal parts (up to 0.0001 inches). Although it gives the thinnest anodizing coatings, it still offers parts with high corrosion resistance. It also provides the lowest absorption of color when dyed.
● Type II: Uses sulfuric acid to make an oxide layer thicker and good for coloring. This makes the aluminum part's surface layer thicker. Type II sulfuric acid anodize has a thickness of 0.0002 to 0.001 inches.
● Type III: It is also known as hard anodizing. It uses the same method as Type II, but its oxide layer is even thicker (> 0.001 inches). Hardcoat anodized parts are the most durable and can take on colors best. But there might be better choices for parts with very tight tolerances.
How to Anodize Metal Parts?
Anodizing can be done to almost any piece of aluminum whether it was made with a CNC machine or by fabricating sheet metal. Even though there are a lot of electrochemical reactions going on, the process is actually quite simple and cheap. Because of this, many industries choose to use anodization. The steps for anodizing may look complicated, but they are not. Here are the main steps in the process of anodizing:
● Step 1: First, the aluminum part has to be neat before anodization can occur. so that it can be anodized, this is necessary to eliminate any impurities that could slow down the process.
● Step 2: The material is then put into a bath of the electrolytic solution, and a direct electric current is passed through it. This makes the aluminum have a positive electric charge, and the electrolyte plates have a negative charge. The resulting electrochemical reaction makes holes in the surface of the aluminum part. These holes let the negatively charged oxygen ions in the solution bond with the aluminum substrate to produce aluminum oxide.
As a result, an anodic oxide barrier layer forms on the part's surface. This barrier layer is stronger and lasts longer than the aluminum below it.
What Are the Benefits of Anodized Aluminum?
Aluminum is a useful material that is used in a lot of different ways. Even though it doesn't rust, it can still be damaged by other things. For instance, oxygen can cause it to wear down and break. These are some of the reasons anodizing aluminum parts is a good idea:
Improved Quality
Anodizing makes the part's surface material properties much better. This includes making it more resistant to corrosion, scratches, and the weather. Also, because the process is electrochemical, the barrier layer made by anodizing becomes a part of the component. This means that it won't chip or peel like paint.
Withstand Heat
The anodized layer on the outside of a part acts as insulation. This means that some parts may conduct electricity less than they did before.
Better Effect on the Surface
Aesthetics is another reason why many people choose to anodize their aluminum items. Anodizing metal parts can also be given a colored finish by anodizing, and there are almost too many colors to choose from. This includes white, black, blue, gold, gray, red, and so on.
Tips for Anodizing Aluminum
Anodizing aluminum parts is a simple process. However, learning some tips will make the process go smoothly. These are some of the essential tips to make the process easy:
Corners And Edges
An important design tip for the anodizing process is to ensure that all of the workpiece's edges and corners have a radius of at least 0.5 mm. Burrs should also not be built into the designs of parts. These design choices are made so that a high electric current concentration doesn't cause the workpiece to get too hot or even catch fire.
Beware of Tolerances
If you know you want to use the anodizing process on your aluminum part, you should know that it will make it thicker. However, this affects tolerance. If it's important to have tight tolerances, think about Type I or Type II anodizing. You can also add extra allowances when making plans.
Consider Other Finishing Methods
Electrochemistry is used in the process of anodizing. So, it works differently than bead blasting or polishing does. If an aluminum part that has been machined goes straight to anodizing, some marks or scratches from the machine will likely be left on the surface of the finished part. Because of this, polishing, bead blasting, or another mechanical finishing process can be helpful if you need a completely even surface finish. The surface of a part will be smoother after it has been anodized.
Work With Batches
It is best to anodize aluminum parts or products in small batches if you want to color them. This ensures the colors are more alike since getting the same color from one batch to the next can be hard. The best way to make sure the color stays the same is to anodize a small number of small parts simultaneously.
What Are the Application of Anodizing Aluminum?
Anodizing is a high-quality and inexpensive way to finish aluminum and other metal parts. Because of this, it is popular and used in a few ways in many different industries. It is used for so many things that you will likely encounter an anodized metal part in your day. Some industries that use anodizing often are aerospace, automotive, architecture, consumer goods, and home goods. Here are a few you can recognize:
● Kitchen equipment.
● Coves for ducts.
● Fixtures for lights.
● Supplies for making food.
● Photo equipment.
● Radio equipment.
● Cases for electronics.
If you need anodized aluminum parts, you can get a quote from Ares Prototyping by uploading your files.
How Can You Tell if the Anodizing Process Worked?
There are different ways to determine if a part has been appropriately anodized. Here are some helpful things you can do:
Color Distribution: A good anodizing process will leave a surface with even color distribution. Anodizing burns, which are caused by high current densities and not enough agitation during the anodizing process, are some things you should look out for on your finished product.
Use an easy scratch test: Use a coin to scratch the aluminum part's surface. If you can see a scratch on the part, it was likely just polished and not anodized. An anodized part will not scratch at all.
See if it has a matte finish: Most of the time, you can tell by the matte finish that comes from anodizing.
Conclusion
Anodizing is an essential part of product manufacturing, and this article will tell you what anodized aluminum is, how to anodize aluminum, and any other tips you need.
At Ares Prototyping, we have many ways to finish metal parts, such as bead blasting, brushing, polishing, electroplating, powder coating, and painting. Anodizing is one of them. Our expert team knows a lot about the anodizing process and guarantees that our customers will get high-quality aluminum parts. Contact any member of the Ares Prototyping team to get a quote or to find out if anodizing is the best way to finish your part or product. We're here to help!
FAQs
How Much Does It Cost to Do Anodizing?
One reason why anodizing is a popular way to finish things is that it is very cheap. But the cost of the process depends on several things. This includes the number of parts, their size and shape, the type of anodizing (the thickness of the coating), and the color.
In short, it will cost more to anodize a complicated part with a color finish than a simple part with no color finish.
Does Anodizing Wear Off?
The anodizing process bonds aluminum parts at the molecular level to make a barrier layer on the surface. This means that, unlike paint, it can't peel or chip off. If the anodizing is done right, the part should only wear for a few decades.
Also, dyed anodized parts that are correctly sealed shouldn't fade for at least five years and often longer. Remember that the part will wear less if the anodized layer is thicker. Type III has the thickest anodized layer.
