I rescued my M3 from the midwest's corrosive winter roads but with 50k miles, it has signs of corrosion underneath. It's not bad but I want to neutralize / eliminate it completely. Is there a powerful, penetrating chemical I can soak the undercarriage with, but yet be safe with wiring, gaskets, and rubber? Or a better procedure?

Do a Google search for Por-15. It's supposed to work wonders. Make sure you coat everything up real nice after you stop the rust, or it'll just come back.