Surface Pre-Treatment
WARNING: This page is about a different car, the 2010 BMW 550i, 2009 BMW 550i, and 2008 BMW 550i. However, it is still accessible from the selected car via links, so may be relevant.
The pre-treatment See 41 00... BONDING STEEL ON STEEL or 41 00... BONDING ALUMINUM ON STEEL depends on the material to be bonded and its coating.