All my major rust spots are gone! nw just that surface rust to deal with..... All spots that had blistered under the floor have been treated with a rust inhibitor called Rust Mort...WORKED great! Then fiberglass several layers of thick fiberglass matting were placed over the spots and hardened with fiberglass on top. It is rock hard no...all the leaky spots have been fixed...I know the engine will last another 6-10 years...I hope the body will to...spray rubberized undercoating his been applied to the undersides of the repaired areas to inhibit moisture and is will be reapplied every 6 months...I will get some pictures up soon...only problems now are some surface rust in the back floor pans under that stupid matting that his cracked The back matting in your passenger compartment crack too? I am scraping off the cracked areas and applying rust or sanding off the surface rust. I hope this work pays off because it looks great!

Some info on Rust Mort....Where'd you get it, how is it applied, what color and how does it function.

JCD

JCD,
I bought my rust mort at an autobody supply shop in Niagara Falls NY (no help to you). This is a great product. I first used it in 1988 on my BMW 2002 I had just purchased. The car quite literally had more rust that paint on the hood, trunk lid and roof. I sanded down the roof, then wire wheeled the pitted spots, applied rust mort,puttied, light sanded then primed and painted. I never had any rust return to the areas I used rust mort. I also used it last year when I stripped and repainted my 300D.
If you are just doing spot rust you should wire wheel to get all the loose rust particles out. The rust mort is applied (sparingly) with a small paint brush. It is clear and watery if you put too much on it takes a long time to dry or harden. You will immediately notice that the rust spot turns black. This is a chemical reaction of what type I don't know. But I was told it oxides the metal which makes further oxidation more difficult. When dry, there appears to be a light film or coating over the rust spot. I assume this is a sealant to stop further air and moisture contact. This in combination with the already oxidized metal stops further rusting. Depending on how badly pitted (how deep the rust went) you may have to put a thin skin of bondo over the spot. I was usually able to get away with a thin application of fairing compound. Of course both of these applications have to be fine sanded or they will show through the paint.
Good luck. But let me say again this product worked very well for me.

found this using google:

http://www.semproducts.com/
http://www.semproducts.com/sempages/semrust.html

Rust-Mort

- Remove loose scale and excess rust with a wire brush. Leave enough rust for the conversion process.
- Apply Rust-Mort with a brush to rusted areas. Do not dilute or reduce. Three to four thin coats are better than one heavy coat s heavy coats will cause slow drying and produce a gummy film. Exces or non-converted Rust-Mort may be removed or loss of adhesion may occur. Wipe the entire area where Rust-Mort was applied with a damp cloth or rinse with water. Make certain all surfaces are completely dry. Allow final coats to dry 24 hours.
- Wipe or rinse with water.
- Proceed with body filler or paint per manufacturer's recommendations.
- For more detailed instructions refer to DRM technical information.