Contact Corrosion
WARNING: This page is about a different car, the 2014 Volkswagen Beetle, 2013 Volkswagen Beetle, and 2012 Volkswagen Beetle. However, it is still accessible from the selected car via links, so may be relevant.
Contact corrosion can occur if incorrect fasteners (bolts, nuts, washers, etc.) are used.
For this reason, only connecting elements with a special surface coating are installed.
Also, rubber or plastic parts and adhesive consist of non-conductive materials.
If there are doubts about whether parts can be used or not, then use new parts.