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  #1  
Old 11-01-2014, 06:53 AM
jibby212 jibby212 is offline
 
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Default anodizing

I work in the aluminum railing trade and use several coating methods but anodizing seems to be one of the better options. I havnt found much info on anodizing complete aircraft, either individual parts or sub assemblies, the company we use has a 20' x 4' tank. I would paint the exterior, anodizing does have insulating properties, don't know if this would affect anything. Any thoughts?
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  #2  
Old 11-01-2014, 07:24 AM
rv7charlie rv7charlie is offline
 
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Default

I'm no expert, but I've read that anodizing reduces fatigue life by around 50%. Not a problem if the part is designed around that knowledge (RV spars are anodized), but could be a real issue if the part isn't designed with that life reduction in mind.

Charlie
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  #3  
Old 11-01-2014, 07:38 AM
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RV7Guy RV7Guy is offline
 
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Default Not completely true

I spent some time with a company in Phx that does all types of coatings. One of their major clients is Boeing helicopters in Mesa. (The Apache) They anodize many parts for the Apache. He said the metal fatigue issue is part of Internet mythology and the overall affect is minimal. I also have a friend and RVer that is an engineer at Boeing helicopters. He said anodizing is not a problem in the fatigue area, but depending on what is anodized and the process it could fade in the Sun over time.

As has already been noted, the most critical part of our planes, the spar, is anodized. So, if you want to bling up a few parts with anodizing........

FYI, the company that is doing some work for me is Futureweld in Phoenix. My POC is Michael Beaver.
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  #4  
Old 11-01-2014, 07:39 AM
chaskuss chaskuss is offline
 
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Charlie is correct that anodizing reduces the fatigue life of aluminum parts by "up to" 50%. The Anodizing process makes the surface of the aluminum brittle. This is why the fatigue life is reduced. Fatigue life reduction is related to the thickness of the coating and the chemicals used. See

http://www.finishing.com/153/54.shtml

http://www.lambdatechs.com/documents/258.pdf

The insulating properties may or may not cause problems with using the airframe as a ground plane for your electrical system.
You might consider Alodining all the parts instead. No reduction of fatigue life with the Alodine process. The shop should be able to Alodine all the parts.
Charlie

Last edited by chaskuss : 11-01-2014 at 07:47 AM. Reason: added web link
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  #5  
Old 11-01-2014, 09:51 AM
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Mike S Mike S is offline
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Default Welcome to VAF!

Jeremy, welcome aboard the good ship VAF
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  #6  
Old 11-01-2014, 04:38 PM
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RV7Guy RV7Guy is offline
 
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Default 5,000,000 cycles

[quote=chaskuss;929640]Charlie is correct that anodizing reduces the fatigue life of aluminum parts by "up to" 50%. The Anodizing process makes the surface of the aluminum brittle. This is why the fatigue life is reduced. Fatigue life reduction is related to the thickness of the coating and the chemicals used. See

The tests cited were for 7000 series aluminums. Not sure we use any 7000 in our planes. Also, failure was listed at 5 million cycles.

I think you guys are concerned about a problem that doesn't exist. As evidence, why are our spars anodized? Should we refuse them? Why aren't spars failing? Why are our AN plumbing fittings anodized blue? Should we be concerned?

I am very confident that the engineers at Boeing would not be anodizing Apache parts if this was a concern. Further, I'm confident that the engineers at Van's would not have anodized the most critical part in our planes, the spar system, if there was concern.

Again, if you want anodize some parts I believe it is safe and you're not likely to experience a problem. The internet is both a blessing and a curse sometimes.
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  #7  
Old 11-01-2014, 07:36 PM
Charles in SC Charles in SC is offline
 
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Is the insulation property thermal or electrical or both?
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  #8  
Old 11-02-2014, 08:11 AM
WingsOnWheels WingsOnWheels is offline
 
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The way a safari helicopter crash some years back due to a control push-pull tube failure. The builder had anodized almost everything. The control tube failed due to fatigue cracking atributed to the anodizing. From what I have read, the issue is more of a concern on thin parts since the anodizing makes up a larger percentage of the cross section.
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  #9  
Old 11-02-2014, 08:19 AM
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Default Hard anodizing

Quote:
Originally Posted by WingsOnWheels View Post
The way a safari helicopter crash some years back due to a control push-pull tube failure. The builder had anodized almost everything. The control tube failed due to fatigue cracking atributed to the anodizing. From what I have read, the issue is more of a concern on thin parts since the anodizing makes up a larger percentage of the cross section.
The Safari crash involved a couple of factors. He had the swashplate control tubes HARD anodized which wear better but makes the metal more brittle. There was a also evidence the control tube contacting the airframe.

Again, I don't believe you will have any issues anodizing parts for cosmetic purposes. I am going to call Van's on Monday and get the specifics of the spar anodizing and their thoughts on additional anodizing.
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  #10  
Old 11-02-2014, 08:32 AM
Adam Adam is offline
 
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I wonder which is worst, spar corrosion or anodizing?
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