Excluding Moisture from Inside of Welded Steel Frame

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I am working on a welded steel frame made of square tubing and I had a question regarding the potential for rust in the frame. The frame will be incased in spray-in foam with composite material outside and wood on the inside. However, I am concerned about purging the frame of all components that could cause rust. I would appreciate feedback on my ideas. 1) Crack open a packet of hand warmers and pour the contents into the framing tube before it is welded. These things mostly contain iron filings and consume all oxygen. A variant is used in long term survival food packing to consume oxygen. 2) Dont bother with the hand warmers and just sweep my shop with a magnetic broom and pour the filings in. It seems to me the rust would attack the easy to corrode iron filings first but i could be wrong. So gas purging is out as I don't have the equipment for it. So I was hoping one of these suggestions might work. Is there another idea I am overlooking? For the outside of the tubing I though of having it powder coated but I dont know if that would interfere with the bond of the adhesive to put on the composite panels. Thanks in advance
Reply:All I've done in the past is drill a small hole, tap it and spray or pour in some rust prevantative. As much as I shouldn't admit it, I've even left a small weld open to do the same and then weld it shut, do that at your own risk tho, probably not a good idea.....Mike
Reply:White rice sucks up moisture if it is that big of a deal you can pour some of minute rice in there before sealing it up. I personally wouldn't worry about it there are tons of pipe rack, glass trucks, and tube frame cars, dune buggies and atvs that don't have anything in side of them and they are fine. Just make sure you put a really good coat of primer on the out side before using the foam or it will rust it under the coating.Vantage 300 kubota ,miller 304 xmt ,lincoln ln 25 pro , ranger 305 G, plenty of other tools of the trade to make the sparks fly.
Reply:I use this in all of my steel bike frameshttp://www.aircraftspruce.com/catalo...clickkey=36927Buy American, or don't whine when you end up on the bread line.
Reply:One question. Will this be completely sealed and air tight when you are done? If so, only so much oxidation is possible. Basic chemistry is on your side in this case. Iron + oxygen = rust. Once the oxygen inside the tubing is used up, no more rusting is possible. This is why a lot of axle builders don't go to extraordinary lengths to coat the insides of their axle tubes before they weld stubs on.
Reply:That is the question I guess. Can I guarantee it will be completely sealed air tight? I dont know. I weld decently with MIG and Fluxcore but I am not a professional like many of you guys. I wouldnt have the equipment to dunk the whole frame in water and look for bubbles, and that would obviously be counter productive anyway.
Reply:To be honest i wouldn't worry about moisture rusting the inside of the frame, you will always get some form of condensation, but not enough to warrant any concern about rust eating away at the insides of the frame.I've seen loads of steel frames go up without any worry about rusting on the inside, if your that  worried about it you could always get the frame galvanized.Normally people worry about rust prevention on the outside, not the inside and i've never seen a frame or tube collapse because its completely rusted away from moisture
Reply:Boiled linseed oil.Its how we treat airframe tubes for corrosion prevention.Syncrowave 350Coolmate 3Millermatic 251Spoolmatic 30A
Reply:Originally Posted by browncoatOne question. Will this be completely sealed and air tight when you are done? If so, only so much oxidation is possible. Basic chemistry is on your side in this case. Iron + oxygen = rust. Once the oxygen inside the tubing is used up, no more rusting is possible. This is why a lot of axle builders don't go to extraordinary lengths to coat the insides of their axle tubes before they weld stubs on.
Reply:Is filling the frame with expanding foam not an option?  If it's filled with foam, there would be no more space for air and moisture to accumulate.  Weld first, then foam fill, then seal filling hole(s).