GM Service Manual Online
For 1990-2009 cars only

The present models use many aluminum components. Aluminum in contact with sheet metal may corrode rapidly if not protected by special finishes or isolators.

These fasteners have a special finish that meets GM specifications. This finish provides adequate protection from corrosion. The special fasteners are a medium blue color. The fasteners differ in color in order to more easily identify them from the standard metric fasteners.