Manganese phosphate plating is a conversion coating process used on ferrous metals—primarily steel—to form a tough, matte layer of manganese phosphate crystals. Known for its wear resistance, lubricant retention, and paint adhesion properties, this coating is widely used in demanding industrial environments.

With its dull, dark gray to black finish, manganese phosphate is also preferred where non-reflective surfaces are important—such as in military applications or moving engine parts.