My car is finally back from the body shop with fresh new floor and trunk pans. The next step is to clean the undercarriage and apply a protective coating, paint, POR, undercoating, etc. The car does not have undercoating, but does have the typical dirt grease, grim, and paint. What is the best method to clean the surface and what would be the best coating to apply for protection?

Just to let you know, I bought a sand blaster and sandblasted the underneath of mine. If you have new floors the may not be necessary. Otherise you may be able to use solvent, steel wool and a wire brush to remove the surface gunk. I then painted mine with PPG black Epoxy. turned out real well but it was a lot of work.

If you have the car apart, I would definately sand blast it. The time and effort you save will be invaluable. If the car is assembled, you can use the solvent method to remove any petroleum based coatings, then wire wheel and clean the exposed metal, treat it, then coat it with whatever coating you decide. I used POR 15 3 years ago on the underside of the 69 and there isn't a spot of rust anywhere. I did the underside of the 75 more than 6 years ago and there isn't any rust under there either.

If you decide to POR15 new floors, you will need to roughen up the surface with a DA or sand blasting, etc. as it will not adhere well even when treating with their products. It needs more 'tooth'. I POR15'd my new floors a few years ago and it's still perfect ( and easy to keep clean ).