PHOSPHATE COATING 101
Another approach to increase corrosion resistance is by producing a protective layer on the surface. One of the most common coatings consists of a phosphate—usually a phosphate of iron, manganese, or zinc. The phosphate coating is produced by placing the object to be coated in phosphoric acid that contains the metal phosphate. As the object to be coated slowly reacts with the acid, the solution becomes less acidic and the metal phosphate is deposited on the surface of the object. Zinc phosphate is used in the coating process on many OKC knives. Corrosion is a problem with any iron-based alloy. As a result, knife blades are made from alloys that are more resistant to corrosion than those made of typical carbon steels. In this regard, high carbon steels such as 420HC or stainless steels are employed.