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Aluminum anodizing/coating, strength and corrosion resistance

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71dsp
#1
Oct4-09, 08:05 PM
P: 12
It's been awhile since I've been on, but I'm still working on my brake system for my track car - http://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:



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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