What to use for paint on a VW chassis.

[modok]

[raygreenwood]

I would agree with that. I really only use rust converter for the areas Modok described.

When I find rust...I endeavor ro remove it all......but you can't get it all unless you are dealing with a flat, wide open sheet of metal.

Its the crevices and joint areas that your sander, grinder or wire brush cant reach into that will kill you in the long run.

If these areas have rust and paint or rust and undercoating......I get the paint or undercoating off of the rust with stripper. Then use acid or Jasco to remove the crusty rust.

Then you are either left with nothing to convert.....or rarely a perfect surface to just paint over....and if you have stripped something bare to metal....you need to be ready to paint it with SOMETHING.....right now. If you can't do that.....its going to flash rust. So thats where the bonus function comes in of then going back with a rust converter when you are ready to paint. And.....there is no sense in my experience with just having spot areas converted. If I am going to use rust converter in an area or on a panel.....I prep to convert the whole panel as evenly as possible.

As for doing this on a whole car body.....sure......it would be a very effective primer.....but with rust converter running about $20 a gallon.....it may be expensive. Ray

[wcfvw69]

I was very underwhelmed with POR-15. It has a high price point and requires lots of labor to prep for it to be laid down. I had a master cylinder leak and it lifted the POR15 up wherever it came in contact with the POR15. It peeled off in sheets.

I'll never use it again. In a perfect world, I'd remove all the rust with media blasting or wire wheel and then acid removal/converter. I'd then mix up and spray epoxy primer followed by a quality automotive 2 part paint. Then, cover it with a product like Ray is suggesting.

As mentioned already, the most important part is to remove and treat the rust or it will come right back.
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[theKbStockpiler]

Look at what you spawned Raygreenwood. All i want to do is use acid now.


I have a rust bucket Cherokee (some say pail) that is on it's third rust out ,is hard to replace based on functionality, and is good practice for my "just barely still practical to restore" 72 super.

As there is the aspect of "only wanting to buy off the shelf", I have been using phosphoric and muriatic acid available from the home centers and have come across these observations.

-If you have a few days time, putting a fresh layer of muriatic acid on a area until it drips off maybe every couple of hours for a few days will remove practically all heavy rust with no physical interaction besides brushing it on.

-With the muriatic/phosphoric mixes like Rustoleum Rust Stripper. the phosphoric acid seems to help the rust from neutralizing the muriatic acid by converting it. The muriatic acid is effective longer and you don't contaminate the container that you are dipping the brush in.

-Some times you will get a lot of flash rust and sometimes you won't. The mix seems to do it the most. I don't think that the muriatic acid contributes to the flash rust at all like I previously thought. Maybe humidity plays a factor as well.

-I used the low fume muriatic acid and you still have to use a fan to remove the vapor from the area. You can actually see vapor evaporate from a open container.

What I have been doing is to not use the mix but to alternate acids. I'll have a area coated with one acid for maybe 4 hours and then use phosphoric for 4 hours. With this method the tough spots that are left last don't seem to resist the muriatic acid ability.

I must say that it is working pretty well.

Also I noticed that if you use phosphoric acid with water added (phosphatizing) even on a thin film of rust ;less than .003, if you scrape the area down to check if the depth of the treatment goes down to bare metal, the converted rust still resembles rust. That or it actually does not work at all. Some treated spots will develop a white covering and usually the thicker rusted area's take multiple coats to develop this.

So listen to ray and start using acid.
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[raygreenwood]

What you are seeing....is that the Muriatic acid acid mix does not get as weak as quick....because its solution strength is MUCH higher than phosphoric acid alone

Whether you get a lot if flash rust or not depends on the steel and local air moisture content.....but no mistake.....muriatic acid will cause flash rust more than just about anything. This is because it causes hydrogenation or hydrogen embrittlement of the surface. I would not use it on steel that is tempered like spring steel or CV shafts. It can weaken the surface.

I have many times.....easily gotten stainless steel to rust. Easy to do....soak it in muriatic acid. First it cleans away any chemical corrosion and staining.....but rinse it and leave it out in the air with no oil.....and it will actually start to surface flash rust. Ray