While painted surfaces and glass tend to receive the most attention in auto detailing, cleaning various other parts is actually more important for maximizing the quality of the finish. Deterioration of window molding, roof rails, etc., and water spots on the B pillar have long been important themes in cleaning. Here, we will provide guidance on how to deal with these problems and what materials to use. Metal molding parts are widely used to project a sense of luxury and enhance the design. Metal molding is used in a variety of locations on the car, such as around the grille and for the window molding and roof rails. While we refer to it as "metal molding" here, the actual material used depends on the part and country of origin. The deterioration of metal molding, commonly seen in cars imported from Europe and other regions, is a problem that has long troubled detailers. This phenomenon occurs particularly often in window molding and roof rails. The part becomes covered in stains, whitens and loses its luster. So, why does this deterioration occur? Let's start by looking at the differences in materials.