Questions about Type III, hard anodizing

One of the questions which I hear from time to time is how sealing influence the properties of the coating. The following questions are some of most common ones regarding sealing of hard anodized coatings.
  • How does hot sealing influencing the abrasion resistant on Type III, hard anodized coatings?
  • Can the parts be hard anodized and dyed black without influence the abrasion resistance?

When you order hard anodizing, you have to decide if you need the highest abrasion resistance of the surface for your application or not. If you do then don´t specify sealing.

As told in an earlier post the aluminum oxide is converted into aluminum hydroxide which are softer and more voluminous during the hot sealing process.

So the question on dyed hard anodized parts has the same answer because you need to seal you parts after the dying.

Yes, You will decrease the abrasion resistance if you dyed the hard coating but you will increase the corrosion resistance and capture your color.

  • How does EN AW 6082 behave during hard anodizing?
Alloy 6082 is doing great when hard anodized. The reason for this is the alloying elements. This alloy has the following composition, which gives absolutely no problems when hard anodizing your part.

  • Is there a difference in abrasion resistance hard anodized between forged material EN AW 6082 T6 and the cast alloy G-AlSi7Mg, and can you hard anodize this alloy at all?

AlSi7Mg has 6 – 8 % silicon which makes it very difficult to do both Type II and Type III anodizing. The oxide layer formed during the anodizing process consist of a lot of small silicon particles which decreases the corrosion resistance and wear resistance.

So yes, there are a huge difference in abrasion resistance of hard anodized forged material EN AW 6082 T6 and cast alloy G-AlSi7Mg.

I will make a future post of what are the best alloys for hard anodizing.

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