The nitriding processes described herein are classified by the result they produce, as follows: Class 0: No white layer permitted. (Not recommended for stainless steels.) Class 1: 0.0005 inch (0.013 mm) maximum white layer thickness permitted. Class 2: 0.001 inch (0.025 mm) maximum white layer thickness permitted. (Not recommended for stainless steels.) If no class is specified, Class 2 applies.