Rust?

Having played with a number of recumbents recently, and spent time dismantling old bikes when I was younger I'm slightly paranoid about open tubes rusting out. I regularly pour rusty water out of my bikes, and that worries me. Especially in the seat where there's a definite depression that will hold water and might rust through. So I want to seal as many tubes as I can, and fit drain holes to the rest. 5mm bidon mounts look good, with the side effect that I can use them to hold toys onto the trike if the placement is well thought out.

Putting fish oil into the tubes seems like a cunning plan, as it soaks up any water that does get in. I want to seal the seat tubes as well as the chainstays and cross member. The main tube is going to be open, so I might settle for sloshing a litre of fish oil in there then draining it into a handy container so I don't lose it when I break the trike down. Like the seat tubes or chainstays.

Actually, using the frame tubes as containers might be a cunning plan. Perhaps more suitable for carrying oil than meths or kero (which power my stove). But the latter would lead to the cool experience of rolling up to a service station and saying "fill her up" to a bemused attendant. However, the need to have a tap mounted on the frame, or else to turn the trike over to pour oil out might make that a bit tricky.