I recently purchased a 996 (37000km) and had the Porsche dealership do the pre-purchase inspection. After I became the owner I took the car to another Porsche maintenance facility to get a general service done as it was overdue for one. I was subsequently surprised to learn that the underside of my car is quite badly corroded i.e. there is surface rust on the underside of all four wheel arch's , also in between the body seals , all the springs/shocks have started to rust and finally all the clips that hold various components to the bottom of car are showing signs of rusting. It may seem as though the car has been submerged in salt water or something , but after much further investigation , the car proved to otherwise be in very good shape.
I have had the wheel arch's sanded back and treated with an anti rust paint and will shortly be having all the clips on the car replaced. Also we are making enquiries as to how to get the underside of the car sprayed with a wax compound that should be the same/similiar to the one that is used on the underside of the car when it leaves the factory.
Does anybody have any experience with this type of problem or any suggestions?

Thanks

 

Sounds like you are on the right track. Just get it cleaned up good and sprayed with something to stop the rust, then a coating of coating....errr yea. Don't know if you can get factory cosmoline sprayed back on somewhere or not.