None or very little metal prep rust preventer

Hey guys I need some ideas on what to use for a cross member in a 50 Dodge, the cross member is 2 part and its hollow between the two parts but access is limited to 2 2" holes one on each bottom side end of the cross member. The metal inside is relatively clean and rust free at this time. Do you know of something I can spray in the two access holes to coat the inside of this cross member to help stop any possible future problems? Now another complication, the entire frame will be going in for powder coating after this rust prevention is done so whatever is used needs to be still there after being baked at 400 degrees for 20 minutes! Any ideas would certainly be appreciated folks.

Thanks
Karl

Cold galvanize paint. That stuff works wonders.

Just saw this yesterday.. Eastwood makes a inner frame rust sealer in a spray can.. Just search, Rust Encapuslator and you’ll see plenty of options.. just be careful of application... some must be used on complete rust only, otherwise they will never harden..

I'd do the rust preventer stuff after it comes back from powder coat.

RickWG said:

I'd do the rust preventer stuff after it comes back from powder coat.

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that's how I would do it than you can use something petroleum based like waxoil or lps 3