SEM Products, Inc. – 3957( ) RUST PREVENTER is a non-hardening internal panel compound to replace OEM corrosion protection on inner body panels. It is semi-transparent black in color and is easily applied to inner panels with a 360° pattern using the 71110 PREMIUM UNDERCOAT GUN & WAND or the 71120 RUST PREVENTER AEROSOL WAND. It’s fast drying formula is a simple way to restore corrosion protection on new parts and replacement panels.