Aluminum anodizing/coating, strength and corrosion resistance

In summary: Your Name]In summary, the forum user is working on their brake system for their track car and is trying to decide on a protective coating for the aluminum parts. They had initially considered anodizing but have discovered that it can compromise the fatigue strength of the material. They are now considering shot peening and are unsure about protecting the material from corrosion. The user is also asking for advice on shot peening critical surfaces and sharing pictures of their progress. Finally, they are seeking guidance on whether anodizing will cause any issues with the pre-made hats they are using and what other coatings they should consider.
  • #1
71dsp
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It's been awhile since I've been on, but I'm still working on my brake system for my track car - https://www.physicsforums.com/showthread.php?t=304215.

I now have the hats and brackets machined, and I'm trying to decide what to do for the finish.

At first I was set on anodizing as it'll improve the wear resistance of the aluminum (good for the brake hats, as the rotors are floating) and protect against corrosion. However, I've been doing some research and it appears that anodizing can seriously compromise the fatigue strength of 7075-T6, especially hard anodizing.

In light of that discovery, I've decided to shot peen the brackets (7075-T6), but I haven't figured out what to do about protecting the material from corrosion. This is for a track only car that will never see street duty, and it's unlikely that it'll see more than one rain event per year. Otherwise it's stored in a garage. Would leaving the aluminum bare be asking for trouble?

The hats are off the shelf units that have been converted to use floating hardware by machining the proper slots in the hat. I do not know what kind of material they're made out of, but I'd guess 6061 based on the cost of the hats themselves and the popularity of 6061 in aftermarket brake parts. I have not been able to find much useful data on the fatigue strength of anodized 6061 or hard anodized 6061. Can anyone tell me if anodization will cause any issues with the hats? Is there another process I should consider? I'm also thinking of having the hats shot peened to increase fatigue strength.

One other question, what is done during shot peening for critical surfaces (such as where the hat interfaces with the hub on the knuckle and where it interfaces with the wheel, etc)?

Here are some pictures so you can get an idea of the configuration of the parts:
http://www.71dsp.net/pics/floating_rotor_conversion/test_fit/4.jpg [Broken]
http://www.71dsp.net/pics/floating_rotor_conversion/test_fit/2.jpg [Broken]

Please note that the pictures were for mock up only. I know the rotor is on backwards, and the bolts on the bracket are common hardware store bolts. The rotors will be installed in the correct orientation and AN7 bolts will be used during the final install.
 
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  • #2

Thank you for sharing your progress on your brake system for your track car. It's always exciting to see fellow enthusiasts working on their own projects.

Regarding your question about protecting the aluminum material from corrosion, it is generally recommended to have some form of protective coating on aluminum to prevent corrosion. While leaving it bare may not cause immediate issues, over time it can lead to degradation and weakening of the material.

Anodizing is a common method of protecting aluminum from corrosion, but as you have discovered, it can also affect the fatigue strength of the material. Anodizing involves creating a layer of oxide on the surface of the aluminum, which can change the surface properties and potentially affect the fatigue strength.

In your case, since this is for a track-only car, it may be worth considering other options such as powder coating or ceramic coating. These methods can also provide corrosion protection while not compromising the fatigue strength of the material.

As for the hats, it is difficult to determine the exact material without knowing the specific brand and model. However, it is safe to assume that they are also made of aluminum, most likely 6061. The same considerations for anodizing and other protective coatings apply to the hats as well.

In terms of shot peening for critical surfaces, it is important to carefully mask off these areas to prevent any damage or changes to their surface properties. It is also recommended to consult with a professional or experienced shot peening service to ensure proper and safe treatment of these critical surfaces.

Overall, it is important to carefully consider the trade-offs between corrosion protection and fatigue strength when choosing a protective coating for your brake system. It may also be helpful to consult with a materials engineer or a specialist in this field for more specific and detailed recommendations.

Best of luck with your project!
 

What is aluminum anodizing?

Aluminum anodizing is an electrochemical process that increases the thickness of the natural oxide layer on the surface of aluminum. This results in a hard, durable, and corrosion-resistant coating that can be dyed in various colors.

How does aluminum anodizing improve strength?

The anodizing process creates a thicker and stronger oxide layer on the surface of aluminum, making it more resistant to scratches and wear. This results in an increase in the overall strength of the metal.

What are the benefits of anodizing aluminum for corrosion resistance?

Anodizing creates a protective layer on the surface of aluminum, making it highly resistant to corrosion from environmental factors such as moisture, saltwater, and chemicals. This makes anodized aluminum ideal for outdoor and marine applications.

What factors affect the strength and corrosion resistance of anodized aluminum?

The thickness of the anodized layer, the quality of the surface preparation, and the type of anodizing process used can all affect the strength and corrosion resistance of anodized aluminum. Additionally, the type of alloy used and the environmental conditions where the aluminum will be used can also play a role.

Can anodizing be removed from aluminum?

Yes, anodizing can be removed through a process called stripping. This involves using chemicals or sandblasting to remove the anodized layer. However, this will also remove any color or dye that was added during the anodizing process and may affect the surface finish of the aluminum.

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