ABSTRACT: Corrosion of steel elements in masonry and concrete structures is a major cause of material and structural damage. Typical steel and iron corrosion damage phenomena are presented. The basic principles of cathodic protection using galvanic anodes or impressed current are explained. Examples of how cathodic protection can be applied to steel reinforcement in reinforced concrete as well as to steel elements in masonry constructions are discussed. In particular the practical impact and advantages of the technique used on historical buildings will be emphasized and clarified with recently executed cathodic protection projects.