Size limitations for anodized parts?

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I am designing the roof of a building that will be assembled from shop-fabricated assemblies consisting of a welded aluminum structural frame (6061-T6) which is glazed using Dow silicone sealant. The aluminum must be anodised or powder coated in order to ensure adhesion of the silicone. Presumably the assembly must be anodized or coated after fabrication because the parts will be welded together. Are there size limitations for anodized items? The assembly will be approx. 10 feet long x 4 feet wide x 15 inches deep.

Roger Cumming
Architect - New York, NY

First of three simultaneous responses -- +++++++

There are no size limitations. It's just a matter of finding a shop with large enough tanks. Your parts are not especially large.

Jeffrey Holmes, CEF
- Spartanburg, SC, USA

Second of three simultaneous responses -- +++++++

There are many job shops in New York State with tanks large enough to take the size you posted.

The only limitation is the size of the tanks, rectifier, and chiller that the anodizer has invested in. Lockheed-Georgia had tanks 80 feet long.

For best quality, all welded assemblies should be of the same alloy.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

Editor's note:
   Mr. Probert is the
   author of Aluminum How-To / Aluminio El Como

Third of three simultaneous responses -- +++++++

Roger,

The only limitation is finding someone with an anodising bath large enough to take your parts. You'll just have to ring round your local suppliers and see if anyone has anything large enough. I'm sure you will find someone but it may mean shipping it a few miles (unless you are really lucky and find one on your doorstep).

Brian Terry
Aerospace - Yeovil, Somerset, UK

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Talk to David Kraft at Anacote in Long Island City. Right across the East River from you, and one of the best job shops around.

Dave Wichern
- The Bronx, New York