What is Aluminum Anodizing Treatment?

Today we'd love to share some knowhow about anodizing which can be done on a range of materials, especially for aluminum alloy, and make the aluminum machined parts practical and beautiful.

What is the Aluminum Anodizing Finish?

Anodizing, sometimes called Type III, offers greater corrosion protection and resistance to wear in extreme environments or with moving mechanical parts subject to a lot of friction. This is produced by continuing the electrical current until the depth of the pores exceeds 10 microns, all the way to 25 microns or even more. This takes more time and is more expensive but produces a superior result.

Does aluminum need corrosion protection?

Although aluminum doesn't rust, it can deteriorate in the presence of oxygen, which is called oxidation. What is oxidation? It simply means to react with oxygen. And oxygen is very reactive, readily forming compounds with most other elements. When aluminum is exposed to the atmosphere it quickly forms a layer of aluminum oxide on the surface, and this layer provides a degree of protection against further corrosion. But aluminum must withstand more than just pure air and water. Acid rain, salt water and other contaminants can still exploit weaknesses in the surface passivation. Even modern alloys will vary in response to this environmental exposure, ranging from mere surface discoloration all the way to mechanical failure.

How is aluminum anodized?

To prepare aluminum for anodizing, the surface is first thoroughly cleaned and rinsed, and then placed into a bath of some electrolytic solution like sulfuric acid. An electrolyte is an electrically conductive solution with lots of positive and negative ions that it wants to swap.

A positive electric charge is applied to the aluminum, making it the “anode”, while a negative charge is applied to plates suspended in the electrolyte. The electric current in this circuit causes positive ions to be attracted to the negative plates, and negative ions to flock to the positive anode, the piece of aluminum.

What is a barrier layer in anodizing?

The electrochemical reaction causes pores to form on the surface of the aluminum as excess positive ions escape. These pores form a geometrically regular pattern and begin to erode down into the substrate. The aluminum at the surface combines with the negatively charged O2 ions to create aluminum oxide. This is called a barrier layer, a defense against further chemical reactions at those spots.

How is color added to metal anodizing?

Colored aluminum is what most of us picture when we think of anodizing. That's the real genius of this process. The nice, stable pores etched into the surface are ideal for introducing tints or pigments. The pigment fills all the empty pores up to the surface, where it’s then permanently sealed off. That’s why anodized colors are so durable – they can’t be scratched off from the surface because in fact the colors are deep down and can only be removed by grinding away the substrate.

Can materials other than aluminum be anodized?

Yes. Anodizing also works with magnesium, titanium and even conductive plastics. It's inexpensive, reliable and eminently durable. That's why it's so commonly used in architectural fittings, because it's both beautiful and almost impervious to the effects of weathering.

Is anodizing right for you?

When you contact us for a free quotation and project review, we'll be able to offer advice on the many different Surface Treatments services that we offer for Aluminum CNC Machining and Aluminum Stamping. So it's best to talk with one of our customer service engineers in advance and do a design review first. We can suggest one or more solutions to achieve exactly the texture you want that fits your schedule and budget.