As mentioned above, deterioration and corrosion of window molding is common on European cars, but rarely seen on Japanese cars. Differences in the materials used for molding play a large part in this. European cars tend to use aluminum for window moldings, while Japanese cars use stainless steel, even for otherwise identical moldings. Why are different materials used for the same part? European manufacturers must have some reason for preferring aluminum, despite stainless steel's reputation for strength and resistance to corrosion. While we cannot decisively state a clear reason, environmental concerns are relevant. European environmental regulations are stricter than most of the world, including with regard to automotive recycling. As such, it appears that aluminum is used because of its excellent recyclability. Of course, there are likely various other reasons, such as cost and ease of use. Let's compare the differences between aluminum and stainless steel.