aluminum 6061 needs coating/sealing?

Finishes, paints and coatings

aluminum 6061 needs coating/sealing?

Postby mboardman » Wed Sep 27, 2017 8:23 am

I was advised by my local supplier that the .020 thickness 6061 alum sheeting would corrode if not sealed quickly with something - paint, clear coat, etc. Not that I doubt it, but it surprised me. Wasnt expecting to have to seal it.

Is this normal? I havent heard of anyone noting this as a final step after their builds, but it makes sense. Ive just never worked with sheet alum before. How do you seal yours?

A can of spray on clear coat from the auto parts store? Will that adhere to the surface of alum?
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Re: aluminum 6061 needs coating/sealing?

Postby absolutsnwbrdr » Wed Sep 27, 2017 11:49 am

Partial exerpt From Wikipedia...
6061 is commonly used for the following:
- construction of aircraft structures, such as wings and fuselages, more commonly in homebuilt aircraft than commercial or military aircraft.[8] 2024 alloy is somewhat stronger, but 6061 is more easily worked and remains resistant to corrosion even when the surface is abraded, which is not the case for 2024, which is usually used with a thin Alclad coating for corrosion resistance
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aluminum 6061 needs coating/sealing?

Postby mcubberley » Wed Sep 27, 2017 2:40 pm

If not coated mill finish will get dull oxides on the outside. This acts as a natural corrosion barrier. Still looks nice once it evens out over time. If you polish it you will need to do that forever unless clear coated after you polish it. You need to make sure that it's the finish you want before you put a clear coat on it. I polished mine once and amount of work that went into that was too much for me to keep up with so I'm gonna let it go natural. I am OK with how that looks in the long run. Make sure any Clearcoat is formulated for aluminum.
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Re: aluminum 6061 needs coating/sealing?

Postby LMarsh » Mon Oct 09, 2017 9:12 pm

If you want to keep the look it has when you buy it, then yes you'll need to clear coat it. Every aluminum part I used on my original build had eventually corroded. Fenders, roof trim, diamond tongue box, etc. The skin could be scratched just by your finger it was so soft (I got my aluminum in a coil from a tractor trailer shop) so I clear coated after I was finished building it, but it was way more difficult. I clear coated everything on builds two and three and my current build I went with anodized. I only get flat sheets now, no more coiled aluminum. Anything not anodized will be clear coated. I'm not expert painter at all, but this is how I've done it myself without having to spray dangerous chemicals, using a product easily applied, and its a better product than rattle can clear:

I used a two part crystal clear coating from POR-15 called Glisten PC. It works great and can be rolled on then self levels very smooth and shiny if you lay your sheets flat. The directions provided by the manufacturer are pretty straight forward. It flexes with the aluminum no problem when bending to your curve. You prep the aluminum with an acid you can buy at the same time, then just rinse it off and dry. Using a foam or low nap roller I just rolled it on and let it cure. Done deal. Obviously keeping the dust to a minimum will help with results but for a complete amateur job it was outstanding. One tip is DO NOT apply a second coat. I tried it and it made a mess, it dissolves the first coat and won't smooth back out. I believe this product has isocyanides in it which is the nasty stuff in automotive paints you don't want to be breathing. I think when not spraying it you're a lot better off and you can get the proper mask too if you want. I never did but if I used it again I would.

I don't think on build 1 I even acid prepped it. It seemed fine even after ~5 years when we sold it. I also spoke with an auto body guy just last week about painting my current build and he didn't want to do it because of adhesion problems with aluminum. I guess powder coating or anodized is the way to go but I had no issues with the Glisten PC and I have scraps from almost 10 years ago that still look brand new.
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