3M™ Cavity Wax Plus is a non-hardening corrosion protective coating for bare or primed aluminum and steel automotive inner body panels and welded structural components. The material is designed to cover and seal interior joints, hem flanges and compromised e-coats where corrosion can form. Properly applied with the 3M™ Cavity Wax Plus Wand Kit, it remains pliable and will not chip, peel or crack.