Parts Coatings - To Coat Or Not To Coat? Part Two Photo Gallery
There are two areas of interest shown here on this Mahle piston. In this picture you can see that the skirt has a coated wear surface intended to reduction friction (decreasing friction horsepower loss). It's a phosphate coating base with a graphite-based coating applied over the phosphate. Engine builder Keith Dorton says that it has worked remarkably well for him.