I recently tried to get 6061 t6 bent locally and failed misserably. Everyone that tried got to 20 degrees and pop... didn't sheer the tube but stress fractured it. I ended up talking a a fellow buzzard into doing it with 6063... Thanks by the way, everyone that sees the rear tubes wants to ditch their NRS and get some...
Any ways back on topic. MRkyak, you seem to be well equipped and at least fairly internet savvy... I researched all this and if I had access to a mandrel bender as you appear to I'd be making all kinds of cool shit. If you want to use pre-annodized NRS tubing you can anneal the tubing back to T0 bend it and supposedly re-temper it (roughly) according to some web surfing I did. The re-temper is all about max temperature and rate of cool but I bet you could figure out how to do it.
I think we largely underestimate the strength of this tubing! I might be worried about oar towers or something hyper critical to functionality but asside from dumping my home bent and tempered frame (If I had gone that route) into the ledge hole in lava with 3k lbs of gear I'm pretty sure no part of it would ever fail under raft loads...
The difference between pipe and tube is simply dimensional and terminology. They each follow a different naming and sizing convention based on the industry they're used in.
Annodization is basically controlled oxidation of the AL. It creates a coating on any exposed surface that penetrates into the substrate a bit and adds a little material to the surface. It can be ground/sanded off and worked with. It does not alter the internal structure of the material (past it's penetration, which is measured in mils)... so yes, to your second post, it's true it does not strengthen the material, just makes it more resistant to wear.
You may see cracks in the annodization if looking with a glass/microscope as it is much harder and stiffer than the substrate, so you may want to sand that off before you judge whether your tubing/pipe is still sound.
Yesterday's gone on down the river and you can't get it back. - Agustus McCrae