How much of a concern is rust INSIDE of a frame? When disassembling one to take to the powder coater, I noticed quite a bit in the top tube. The downtube (at least what I can see) and bottom bracket don't particularly worry me, and the seat tube looks easy enough to clean up with a shotgun brush and some oil, but the top tube is worrysome, a) because I don't have any sort of borescope to see how extensive the damage is, and b) because the rust is bright orange and appears there may be moisture in there. I don't really want to spend money on a powder coat job if this is something that is going to ruin the frame in the next couple years.

I tried to get a picture to exhibit my concern. I should say this is only a concern on the front of the top tube, the back by the seat tube looks pretty dry and just a light surface rust inside.