I think the is question is what are you trying to accomplish? Is paint an aesthetic? Want the frame to look pretty? My frame has lots of welding. Rowframe Gary knows his shit when it comes to to metallurgy, coatings, and welding. I've met him, I work in industry. My company has the largest aluminum heat treat furnace in the state; we cast and machine 3 million dollars worth of aluminum a year.
Has anybody in the community had a frame break (in a nasty rapid, hole, etc) that can be attributed to the coating or welding process? All my youtube vids show frames blowing off rafts seem to be straps or d-ring failure. Arguing about 12kpsi to a t5 vs/ a t6/t651 temper is ludicrous if the frame is not going to break during even extra-ordinary circumstance. part of engineering is understanding the use and abuse of a part, not just "make it as strong as we can".
As far as mil-spec anodize/coating. We do this. For General dynamics. Lockheed, Raytheon, and many others. The mil-spec matches the conditions. Mil-spec is NOT better, it is just very specific to the 'mission requirements.' If somebody can show me a mil-spec for a whitewater raft frame, then I will take stock in their decisions. Otherwise.. it's apples to oranges. Anodize is very susceptible to scratches. Repair on anodize means stripping and starting over. Paint..... spray spray. Application people.
My frame is uncoated. My raft is grey. My calves are grey after a river trip 'cause they rub the frame rail behind them. I'm on the river. 'nuff said.