Floor pan repair

[60series]

Hi all, 

 

This is my first post, thanks for letting me join the forums. I was unsure what thread to post this under so sorry if it's wrong. I have a 1986 Toyota 60 Series landcruiser with rusty floor pans. I've never ever done any panel repair but was told floor pans are quite easy to do. I asked the panel shop and they said if i don't get rid of the 'black pitting' from the metal it'll continue to rust no matter what. I sandblasted the worst of it and cut the worst of it but have some black pitting left in other spots. 

 

I thought that if you used the right rust converter, and primed and painted it that would remove the oxygen/water from it and once it's sealed it would be impossible for it to rust since rust needs oxygen? I was then going to paint and seal the underside of the pans. Sorry if i'm using broad terms, i'm just very new to this. I do trust the shop, they've done heaps of work for me and it's always been 100% and i am returning soon for more work but was hoping to do my floors myself as a learning curve. 

 

Thanks! 

[jan arnett (2)]

Welcome aboard.  You are asking a question which you will get many answers and so far you have done every thing correctly.  The only thing that will stop rust completely is new metal and even that isn't fool proof.  The second thing you can do is sand blast the metal which you did and now is where you will get differences of opinion.  The black pits are as you said rust pits and will ultimately rerust and the question is when.  Some people like converters but I do not.  Most of the good reviews come from the companies selling them.  There are many products which contain phosphoric acid which I prefer.  (navel jelly).  If it were a smaller item I prefer electrolysis.

 

You are correct in trying to seal the metal and you should use a epoxy primer followed by a 2K primer.  I like Southern Polly products.

[jan arnett (2)]

Here are the products I use. 

 

https://www.southernpolyurethanes.com/perfect-paint-job

 

 

[Bhigdog]

It's a floor pan. Sand blast and brush on 2 wets coats of POR 15 ..............Bob

[plymouthcranbrook]

I used POR 15 on my 52 15 years ago and so far no rust has been found.  One thing is to see if the floors are too rotted to be safe. That changes everything.

Edited May 12, 2019 by plymouthcranbrook (see edit history)

[Dave Henderson]

The floor pans rusted because of a leak somewhere.  Fixing just the pans is only half the job.  You wouldn't be happy if the repaired pans rusted too after all your work.  Bite the bullet and find out where water is leaking in and fix that too .  

[60series]

8 hours ago, Dave Henderson said:

The floor pans rusted because of a leak somewhere.  Fixing just the pans is only half the job.  You wouldn't be happy if the repaired pans rusted too after all your work.  Bite the bullet and find out where water is leaking in and fix that too .  

Thanks for the reply, definitely no leaks. I’d say it’s been off road and it would’ve taken off water then Rusted from there. 

[Akstraw]

I agree with you.  Rust=oxidation.  Block the oxygen, and you will prevent the rust.

[Dave Henderson]

A technique that I'm told was used by the Navy to prevent re rusting is to pass a torch over the surface until moisture appears.  After it evaporates from the heat the surface is ready to coat (promptly).  You might be surprised at how much moisture is released by the heat from a surface that appears dry.  

[Bloo]

2 hours ago, Dave Henderson said:

A technique that I'm told was used by the Navy to prevent re rusting is to pass a torch over the surface until moisture appears.  After it evaporates from the heat the surface is ready to coat (promptly).  You might be surprised at how much moisture is released by the heat from a surface that appears dry.  

 

I do that. It is almost imperative when painting aluminum castings, but works on sheetmetal, too.

 

Up here in Central Washington, you can indeed get rusty floor pans without a leak. In this climate, whatever stays wet is what rusts (no road salt). Cars with rubber floor covering historically were the ones with no floor pans left. Snow gets in in the wintertime, the jute padding gets wet, and the rubber prevents the water from evaporating. Cars with carpet typically had no serious floor rust. Cars with rubber mats had no floor left. The water just sits there for years until the floors fall out.

 

 

[R Walling]

On 5/12/2019 at 4:26 PM, Bhigdog said:

It's a floor pan. Sand blast and brush on 2 wets coats of POR 15 ..............Bob

 

POR will only have a mechanical bond if not applied over rust.

 If you want to sand blast, spray water on it to allow it to rust and then apply POR

[Graham Man]

How long do you want it to last?  It took 33 years of someone not caring about it to get rusty.  Clean it up, if the steel is still solid, coat it with your favorite coating and keep it dry, the floor will outlast all of us. 

[56Roadmaster]

On the Navy technique, that's used to check preheat for welding where approximately room temp (60F) minimum preheat is required. The source of the moisture is really the water vapor as result of burning a hydrocarbon fuel (acetylene, propane etc.). The basic combustion products are H20 and CO2 always. Once the metal heats up the water vapor no longer condenses, and yes there is a lot of water that will condense. Try your propane torch on a cold piece of material and you'll see.

[Bloo]

1 hour ago, 56Roadmaster said:

The source of the moisture is really the water vapor as result of burning a hydrocarbon fuel (acetylene, propane etc.).

 

That is true, but you can SEE it, and in a wet climate (like Seattle for instance) it also proves that the water that was already on the part (that you couldn't see) has boiled off.

Edited May 20, 2019 by Bloo (see edit history)

[JamesR]

On 5/17/2019 at 10:11 AM, Graham Man said:

How long do you want it to last?  It took 33 years of someone not caring about it to get rusty.  Clean it up, if the steel is still solid, coat it with your favorite coating and keep it dry, the floor will outlast all of us. 

 

I agree with Graham Man and the people who recommended POR 15. I used it on the interior side of a floor pan about 11 or 12 years ago. I pulled some of my carpet up this winter for unrelated work and I didn't see any reappearance of rust. Prior to putting the stuff on back then, the interior side of the surface had a fair amount of surface rust due to window leakage combined with outdoor storage. POR -15 is a great product for restored vehicles that will be used, maintained and stored like most restored vehicles (sparing and well protected.) You could probably expect the coating to last indefinitely. However, for everyday drivers that will be exposed to the elements (and especially snow and salt) you probably shouldn't expect it to last as long, though it will still protect pretty well. Follow the instructions: rust free metal - like a new floor pan - has to be treated before the coating is applied.