I want to share my experience for a waterproof rust proof paint that I have used over the years to cover steel car sections like floor and inside doors which doesn't cost the earth and is very resilient. It is particularly good for floors which occasionally get wet.

Use it if you like and see how it goes but of course no responsibility for me. But it works.

I learned this on the worst rust car that Holden ever produced, the HD/HR Holden which leaked like a sieve and had rust installed as a free accessory during manufacture. These cars predate most of you but some on the forum will attest to the standard of mid 60's Australian cars when it came to water tightness and rust protection.

Treat the rust with phosphoric acid/rust converter, neutralise if required by the manufacturer's instructions etc then prime with standard steel red primer making sure you get it into the hidden bits. This is pretty easy. For simplicity I just used to use things like Killrust converter and primer.

Buy black bituminous paint used for sealing gutters like Ormonoid or the really thick paste like material that you spatula on from the same manufacturer and cover everything you want treated. Of course this stuff smells is terribly sticky and this process is more for vehicles being restored than for daily drivers but if you can stand the smell and can put some paper down you can do it and drive. Make sure you wear disposable gloves.

Leave it to dry until reasonably tack free. Depending on the temperature this can take a week or so, or longer.

When you think it is reasonably dry add the magic ingredient. Buy some Estapol 2 part floor varnish like 7008 then liberally apply over the bitumen paint, pouring it where possible into door seams etc to get the full covering. This serves to seal the stickiness and provide a rock hard impact resistant and waterproof layer(s).

I've tried both one part and 2 part and both work but 2 part is more resilient. I guess it is moisture cured polyurethane like POR15 and is very tough. Re coat to your heart's content. It goes a little glassy and yellow the more coats you add and you can get quite a thickness up. It dries pretty quick and can be recoated as per Estapol's instructions. I just laid tacky coat over tacky coat and had no problems.

When hard you can hit it with a hammer and not crack it. I have not had any crack and flake off despite how much flex there is in the body or floor pan. Admittedly I haven't used it near exhaust etc but it is perfect for VW floor pans that are treated and not requiring say a POR15 treatment.

I have just found an old HR door treated and left under the house over 30 years ago and the inside of the door is like the day I did it but the outside is showing external mild corrosion. This is what has prompted me to write this up.

Of course if you don't treat the underlying rust issue it will grow rust underneath. But this process will ensure you can have moisture and sweating and not worry about the water penetrating to the substrate.

As they say in the blurbs "try it out on a hidden piece first to see if it does not cause an allergic reaction".

Cost is not bad, you can mix only what you need and you can buy all you need in the next trip to one of the monopolising retail hardware giants. Adding the bituminous paint and Estapol provides a degree of sound proofing by removing druminess as well.

Enjoy.

viiking

Nice tip, cheers mate.

Sounds like a good treatment, but if your in a hurry and are a tightarse like me then try a 50/50 mix of zinc phosphate metal primer and penetrol. Then a coat of dulux metalshield with 20% penetrol added. All these products are reasonably priced and easy to get but will give you a hard glossy finish that will last for years. This treatment doesn't help with sound proofing though.

Great tip too. But what does the Penetrol help with?

Penetrol helps the paint penetrate where it normally wouldn't go like pin holes and tiny gaps and it stops moisture/air from getting under paint. Added benefit is it increases flow for a smoother finish

I know it was a month ago now, but I only just saw this info.

By Estapol, do you mean just full gloss clear floor coatings? Like for timber flooring?

If so, have you also tried it as a super hard durable top coat for the bottom of the floorpans?

I'm still trying to see something better overall than Kill Rust or Wattyl Hi-Lite (yes, the guttering paint, very hard gloss finish) for a gravel runner, hence the question. I'm uncertain of POR15 being much better, and I've been told Rust Bullet will chip off (and it's damn expensive).

Thanks for the info Viking,

Like you I have experimented with a lot of stuff over the years, and have come to a similar conclusion to you!! What I do different though is not use estapol. I have been trialling some in the wheel wells, so exposed to everything the tires throw up. I have been painting over the top with an enamel paint, I pick something close to the body colour as I like having that the same colour in there. It also is standing up very well, and like the estapol sets hard so no longer tacky for grit to stick to, easier to clean and seems to stand up well.

Great post!!

PS I have heard a lot about POR15, but to date have not tried any. Will have to one day.

Grinderman is right: A product like Galmet (brand name) primer is good under an oil based enamel top coat. It's oil based zinc laden primer paint so dont try to spray acrylic over the top.
Galmet is available in red or grey. It takes a few days to dry out but everything I have ever painted in it hasn't rusted. You can spray paint it too.

POR15 etches the steel initially and then prevents oxygen getting to the steel so it arrests rust, but it doesnt stop it. Damage that layer and the rust will continue in earnest.

Even I am going to try a bit of Estapol with some enamel and see if that works. (dunno though)

Cheers,

Ian

Re the bottom of pans. No I haven't but it is rock hard and resists hammer blows so I cant see why it wouldn't work .

Sounds good.....you could call it 'POOR 15'....