I had a chance to take another look yesterday, along with my A&P building partner who inspected everything visually, in detail. Here's some more information.
In spite of what the pictures look like, we saw no rivet heads with corrosion under them (probably light reflecting in the photos), nor did we see any bulging areas anywhere. There is light pitting distributed across the external surface of the parts. So the seller gave us some 1500 wet/dry paper and the pitting disappeared easily, leaving the Alclad intact.
Of more concern to my A&P friend were some dings and scratches that will need to be repaired, and that would give me the chance to get inside a few structures. When one door closes, another one opens...
The light spotty corrosion in one area of both QB wings may be because QB wings come without the bottom skins riveted in, and in this case the builder didn't prime before assembling the last skins.
The area that looks like rust at the bottom of the firewall in one of the photos cleaned up nicely with water and a rag.
I spoke with a person with expertise in light aircraft metallurgy and paint, and he suggested that light corrosion on QB assemblies might be the remnants from the salt air of the Phillipines, exacerbated by being cooped up in a hangar with no circulation for a couple of years, along with the summer heat around here. He also posited that the light corrosion I see is unlikely to progress much once the plane is in an environment with normal circulation and ventilation.
I thought the powder-coated parts were bad until my friend pointed out the torque tube one was attached to. It looked like someone had taunted a Doberman with it. And the Doberman might have been carrying a pipe wrench.
By the way, the zip ties several people have commented on are only keeping the wires from tangling or falling into the wing while it is stored. On the other hand, they'll all need to have new terminations on both ends.
Thanks for all of your observations and opinions. This is just the second time I've posted a question on VAF, but both times I've been impressed with how responsive and helpful my 21,000 or so new aviation friends are.
I hope to meet some more of you at the various RV soirees at KOSH.
Drilling out rivets since 8/19
Adopted RV10 in pieces and parts
RV Assembly Workshop - KOSH 2018