rustproof inside the doors?

I think it depends on if you plan to expose it to water.

If you live in a high-humidity area, plan to drive the car in the wet or wash it with the hose you should probably put something over the bare metal areas.

 

You definitely need to do something.

Use Dinitrol RC rust converter, it adds a film to the rust and stops it dead in its tracks. Once dry then coat with ML

Waxoyl is another good product too.

Classic Cars Dinitrol ML3125 Dinitrol 4941

 

go to the dinitrol link and it tells you all about it.

 

I would use waxoyl

Waxoyl USA

 

Rust Reformer by RustOleum chemically converts rust to a black state which then CAN be painted if you choose to. When I got my car 20 yrs ago I painted this stuff on various underbody areas (inside the fenders by the headlights, etc) where I could see surface rust and it still looks the same. I think I got my last little jug at Pep Boys.

I have heard of people using POR but never have myself, and Waxoyl has been used in England for decades.

 

My problem with painting is that you could miss a bit in difficult to reach places, Waxoyl when applied hot (warm the can in a container of hot water) will creep everywhere and into the small cracks and seams. When it goes cold it dries to a semi hard state and is totally water proof.

Perfect for inside 246 cills, doors and under wing areas etc

 

POR15 is excellent. It is necessary to carefully prepare the surface according to the directions (always good advice). It's practically a bulletproof coating when it dries.

 

Agreed POR15 is a superb product. There is tons of information on it all over the internet so it is pretty easy to get some good research done before choosing to use it.

 

I have a body shop friend that uses automatic transmission fluid and swears by it. Make sure any drain passages are clear and wiring is covered and spray in the door.

 

The Rust Reformer is a low-viscosity liquid, so it would run into small spaces well.
I like that it chemically transforms rust into another inert compound.
I guess you could apply Waxoyl over it if you wanted to after it has dried

If you plan to spray the entire inside surfaces of sills, then you will need a more viscous material like Waxoyl so it will cling to the upper horizontal surfaces. Sounds like Waxoyl is similar to the Ziebart rust preventive treatments of old.

In any case the most important thing is to make sure the drainage holes are not blocked.

 

Jim
Waxoyl & Dinitrol does the same thing by turning rust into an inert compound, apparently it also has the properties to soak into existing paintwork and attack rust beneath the paint. Something some products cannot do
Cheers
Tony