What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

anodizing

jibby212

Well Known Member
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?
 
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
 
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.
 
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:
5,000,000 cycles

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.
 
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.
 
Hard anodizing

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.
 
On the Curtiss P-40 almost every single part of the airframe was anodized. It was purely done for corrosion protection. Granted, they weren't expected to last long but the airframe did see a lot of different vibrations in that time.
 
the insulating properties are electrical, the anodizing would be strictly for corrosion resistance, I live by the Gulf of Mexico and have had corrosion issues on my polished Hummel until I painted it. It would also be less labor than the alodine process and lighter than primer. If there is a possibility of fatigue issues I will stay away from it. This place is great, thanks for all the response.
 
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?

A 12/91 article in the RVator claims a safe limit of 12k hours for the anodized spar and 24k hours for the non-anodized spar in an aircraft that sees regular aerobatic use.

You can certainly draw your own conclusions from this - I did, and my spar is not anodized. But then again, my plane sees regular aerobatic use. No doubt the cross-country cruisers can safely get to much more than 12k hours with an anodized spar.
 
Back
Top