I have some very slight surface rust...I sanded it back and just put some rust preventative primer over it to seal the surface. There's a little bit of very slight surface rust behind the seam of the front windscreen which I can't get to...about the only thing I could do is spray some stuff up there... What's the best thing to stop it spreading? Should I get some kind of anti-rust stuff and spray it up in there just to stop it potentially getting worse? Or just some fish oil or something?

Quote: Originally Posted by Pishk What's the best thing to stop it spreading? Should I get some kind of anti-rust stuff and spray it up in there just to stop it potentially getting worse? Or just some fish oil or something? Chop it out entirely, either replace the entire panel or part of the panel, make sure there's no rust and repaint.

There's no need to 'chop it out'...it's not proper rust, its just discolouration on the surface. It'd take 10seconds to rub it off with fine sandpaper if I could get to it. The only part I can't get with the sandpaper is where there's like supports welded across the roof. The car was just resprayed and some moisture got inside, and there was a few bits of discolouration here and there because the factory paint inside the car is pretty thin. I'm not going to chop up the whole roof for that.

Sorry, didn't see that it said light surface rust. You've answered your own question either way - sand it back, treat it, repaint.

I did that! There's a few bits that are physically impossible to sand back...I'm wanting to know what's the best thing to put on it! Either just something like a fish oil to stop it spreading, or an actual rust converter? Maybe I'll do both! try spray some converter up there, let it dry, then hit it with some oil. Anyway, cheers for the help.

Proper Rust???? How much penetration is too much Or is any penetration mean it's time to chop and weld???? Is there a product/light you can use on your bare metal to test for any rust traces left to grow? Cheers this has been heaps helpful.

product i use is tergo blackguard. is a primer as well. costs $36 nz / litre and i did 2 coats in boot rear screen and under car to front of diff. now all of underside has been sanded back and 2coats blackguard and 1 coat marine 2pak. should last another 20 yrs i reckon. Some original photos have not been recovered yet.