Under Car Rust Proofing
 

I have been working on replacing the diff housing on my wife's 97. Every single bolt seems to be rusted in place on this thing. It has more rust on it than my 91 that has more than double the miles than hers (200+k).
So while I have alot of stuff out of the way I was wondering if there is a good undecoating or rust treatment that I can spray or somehow apply to the underside of the car to all these rusty parts to prevent them from getting any worse and possibly loosen them up? Right now PB blaster and WD-40 are my best friends to get the stuff out, but am looking for a long term protectant.
I noticed a while ago that my VW's have almost a thick grease like coating in some areas on top of the heavy rubberized undercoating for corrosion protection, does anyone know how to get a hold of that stuff or what it is called?

i take mine to schmitts auto body near work, they use the runny oily stuff, its a mess, but it works sooo well. im due again, but i gotta paint it first or theyll kill me....lol.... its like spraying lucas, its really thick aerated oil.... i paid like 120 for it with tax i think....

I have my dad's Jetta at the body shop right now and my wifes 97 is about to go in for repairs as well. I will ask them about it while they have her miata for the respray.
Thanks
Are there any DIY type oils or sealers? I found some rust converter type coatings, but they seem to be more for paint prep and sealing.

Up north they use and shops regularly apply Cosmolene inside bodys and under to cars to help keep from rusting. 20 years ago it was essential for all casr to get the treatment, but today with better metals, drainage and protection on cars cosmolene undercoating isnt done as much.

If your looking for a solution. Try POR15 Off roaders use it, seals out the wet, etc.

http://www.por15.com/CHASSIS-COAT-BL...oductinfo/CHG/

Its not going to do anything to help your present rusted bolt situation, but will slow down the future rust process. and apply the coating your looking for.

+1 on POR15.....shit is fuckin awesome.

Kroil is the # 1 "liquid wrench".

I guess I should have mentioned I am from down South as well. I don't have to deal with salty roads and crap. We bought this car from a coastal town and thats where the rust comes from.

I am mostly worried about slowing the rusting process down so the whole car won't br a rust bucket in a few years.

Ill have to look into the POR 15. I just had someone at work tell me about it too.
The only thing im not sure about is that it looks like POR 15 is to be applied to begin with to prevent rust. I doubt I can apply it over rust. I sure do not feel like taking the time to wirebrush everything under the car before painting.