Protecting the surface of metals

The affinity of some metals in a corrosive environment initially increases normally with increasing concentration of corrosive agents (oxidizing power of the solution), and metal corrosion is intensified, but at a certain concentration of corrosive agents, the corrosion rate suddenly decreases significantly and the metal loses its affinity and becomes inactive. The reason for the reduction in corrosion at a certain concentration of oxidizing components is the formation of a protective or inactive layer on the metal surface. The protective layer can be oxide, hydroxide or other compounds. This phenomenon is called rusting.