Rust proofing suggestions
 

I've got some metal work to do on my hood, not enough to warrant separation of the skin and braces ( I hope). If I don't split the hood open there will for sure be some surface rust left inside the braces and on the bottom side of the skin where it is covered by braces. I'm wondering what would be the best method to stabilize the rust that will remain in those cavities?

Would it be wiser to apply this treatment before exterior paint, or after paint? I want to make sure I don't do anything to contaminate any surface before I paint it. I realize nothing should be getting through to the exterior surface ... but you know how things have a habit of migrating to the worse possible places.

Thanks

Check out Gibbs Penetrant.
Manic in a can.

I would use cavity wax after paint.

Don

I meant MAJIC in a can.

It can be painted over when it dry's.

3M Cavity Wax is always good for protecting “hidden” areas.

I’m trying Noxudol branded stuff that’s similar now. Should have it sprayed within the next few days. Heard good things, I’ll report back.

I use 2 products. KBS Cavity Wax comes aerosol with a wand that fits into a 1/8" hole and sprays 360 degrees. I also use Fluid Film for large open areas where I want a solid transparent or black film that won't wash off. Fluid film stays tacky for a long time (maybe years) unexposed. I've been using these products for a long time. I spray the door jams and entire underneath of my '96 GMC Pickup every fall with Fluid Film and it is in darn good shape, for being in Michigan with salt and road chemicals. I use cavity wax in the rockers, cab corners, tailgate. Both available on Amazon. Just took these cell phone pics and they are upside down.
Use after painting is complete.
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Some things are just too tight to try to spray into. I used Rustoleum rust transformer. Neutralizes and transforms rust to metal. It's in a small plastic bottle. I use a small brush to allow it to flow/drip/run into tight crevices like parts of a hood. It goes on whitish and turns black when dry. Works well. I once painted the rusty tail pipe on my 46 Willys Jeep and it stayed balck and rust free for over 10 years until I sold it.

I used Rustoleum Rust Reformer on the underside of the floors and in other surfaces of my surface Rusted Pontiac. I used a siphon air gun to spray the liquid into the pinch welds and hard to reach areas. As stated above, it dries to form a base that will prevent further rust, and can be painted over. I paid around $9.00 for a 6 ounce bottle. I used about six of those small bottles to do the firewall back to the rear axle, covering all of the passenger floors and inside of the frame rails. After that job, I inquired at the local hardware store about buying the rust reformer in a more economical bulk size. They recommended a Benjamin Moore product called COROTECH RUST ARRESTOR . I paid about $64 for a gallon of that product. I did another vehicle, From the underside of the radiator support front suspension and firewall back to the rear bumper including the floors frame rear suspension etc. with it. Same application method. and used the whole gallon. It looks great as-is , but will be going over it with chassis black. It seems to have done the job very well, and I'll use it again and recommend it for protecting hard to reach places.

I like eastwood frame encapsulator. I have used cavity wax, but not on rust, just finished areas I can get epoxy on.
The eastwood stuff converts, and does Not dry super hard, so it doesn't crack after a while