Moisture in frame rails?

[redss86]

O.k. fabricators,

I have partially rebuilt my frame out of square and rect. tubing. My question is if I should drill some holes in the tubes to allow any moisture out that could accumulate in the tubes. I don't think I really need to do this, but I have been told I might need to. If I do this it would only be like a 3/16" hole, and I would do it before I have the frame powdercoated.

Thanks in advance,
Joe

[MoeBawlz]

There was some talk on CC.com about this recently. If your frame were sealed you could fill it with an inert gas but since this will have openings some people were saying you can spray some sort of wax or something like that on the insides of the tubing so that it will not corrode.

[redss86]

That is a good idea, but I can't get to the insides of all the tubes. Some of the tubes are completely sealed on both ends w/ welds. Kind of wandering if I should be concerned w/ moisture condensing inside these sealed tubes?

Any and all other input is welcome,
Joe

[Matt@RFR]

Either way, you're walking a fine line...spray a rust inhibitor inside individual tubes before assembly and you run a big risk of contaminating your welds either with spreading it unintentionally, or via full penetration at any point in the weld.

Filling the completed chassis with an inert gas (argon, helium, etc.) is a viable option, but not one most home builders will tackle. You can't just pressurize the chassis with inert gas; all that would do is pressurize the existing oxygen in the tubing with a tiny head of argon. For an argon purge, you have to fill the chassis from its lowest point, and vent the chassis at its highest point because argon is heavier than air. The opposite holds true for helium. How do you know when the chassis is completely purged? You don't. You do your best math, plus some fudge factor, and hope for the best.

Strictly from personal experience, 100% of the tube chassis' I've been involved with or have known about were open to atmosphere with no rust preventitive at all, and all are doing well.

If you're thrashing any kind of horsepower in a race-type environment, your chassis will be ready for replacement well before rust renders it unserviceable.

[FCRacing]

Hey J, I have to agree with Matt I have worked on chassis we built back in the mid 80s and cut back into them with little aparent loss, don't worry about it...........this is asuming of course your welds are complete and continuing moisture can not get into the tube ,say when washing the car..........Rhys FCRacing

[redss86]

Thanks for the help guys,

All the cross member tubes are completely sealed on both ends. However, the perimeter rails are open at both ends, inside the remaining part of the original frame. Should I be concerned about this? For water to get inside this portion, it would either have to travel all the way down the inside of the frame from the front or the rear; or it would have to be splashed up through a body mount hole. I don't think I really need to worry about this, but I thought I would ask.

Thanks again,
Joe

[FCRacing]

Hey Joe, Any place were the water can get in could be a problem, can you "cap weld" a cover over those open tube ends??

[redss86]

Not anymore, it is all welded together, w/ the open ends tucked inside the original rails. I am not going to cut it back apart at this point to do it. Any suggestions on putting a coating inside the rails?

Joe

[FCRacing]

Ya Ok I see what your doing...............I really cant see anyway to coat them now so I would just call it good, and let her go.......R

[Matt@RFR]

Yep, just drill a couple small drain holes in appropriate spots and call it good.

[redss86]

I just need to drill some drain holes in the tubes that are open on the ends, correct?

[CAMAROBOY69]

Like mentioned a couple times. I would just drill a very small hole or 2 where necessary. As you accelerate, any moisture will go towards the back of the car. That would be a good spot to drill. Make sure to coat the drilled hole in undercoating or some sort of protection that way the bare hole doesn't rust.
If you are in a climate that doesnt fluctuate all the time then you will be fine. Here in michigan our climate is rediculous. Anywhere from -5degrees up to 100 degrees all in one year. Moisture is our major battle along with snow and salt.

[redss86]

If you are in a climate that doesnt fluctuate all the time then you will be fine. .

Whats that? I wish I did, but I live in south central IL. I see very similar weather as you. It just might get a little colder for you.

Joe

[TT402LS1]

I use to do body work for a living. We used a rust preventor called "Seal Out". You can drill small drain holes and spray this stuff into your rails, with a fexable hose. It is a water proof sealer that "crawls"(or expands), so all areas will get coated even if you cant directly spray it everywhere.