So my 4th gen is getting rusty after 17years in ohio, the underbody is heavily rusted. I love the car and would like to find an alternative, but the one I have is exactly all the options I want.

I've seen advertised chemicals you can submerse for 24hours and it will remove all the rust. But I'm looking for something I could easily apply to the underbody of my car.

I've also seen converter sprays, which supposedly conert the rust to a moisture sealant

 

I've used this stuff a number times with good results.

https://www.theruststore.com/Categor...FQqPaQodBmYGAg

Only catch is that once treated, the surface needs to be coated.

Other than undercoating, I'm not sure what one would do to an automotive underbody.

 

Por-15

 

por 1 is the best I have used. Clean metal as good as you can and put on a few coats.
I have not found one product that will permanently eliminate rust. Its cancer, you can fight it back for a long time, but in the end, it will come back and win. That being said, you might be able to hold the rust at bay for a few years

 

IMHO the only real fix is to cut it out and replace it, but that requires a skill level and labor commitment that may very well total the car.

Vinegar will remove rust, vinegar with salt will remove it even faster. Handy for loose bolts but not so effective on parts that can't be submerged for long periods of time.

Products like Eastwood Fast Etch and KBS RustBlast (essentially the same thing) are a good first step.

Paintwise, POR15 has the market saturation but if you're looking for something a little cheaper and equally effective try KBS Rust Seal.

The more labor you put into it, the more you'll get out of it. Pick up a grinder with a wire wheel. No chemical in the world will help you if you paint it over a flake.