Surface pre-treatment
WARNING: This page is about a different car, the 2011 BMW 750xi, 2011 BMW 750Lxi, 2010 BMW 750xi, and 2010 BMW 750Lxi. However, it is still accessible from the selected car via links, so may be relevant.
The pre-treatment depends on the material to be bonded and its coating. See BONDING STEEL ON STEEL or BONDING ALUMINIUM ON STEEL .