Cathodic protection is the application of an electrically conductive layer to an electrochemical cell, which in turn controls the electrolytic corrosion of the material being protected. An easy method of protection consists of connecting the cathodic metal object to a sacrificial metal that can be corroded easily to act as an anode. The metal cathodic protection is applied to the cathode through a metal contact that is made by melting or fusing the sacrificial material to the metal cathodic protection. This is typically done by soldering or bonding the materials. The application of cathodic protection requires some understanding of how the electrochemical reactions that lead to the formation of electrochemicals take place, as well as knowledge of the physical properties of the materials used to protect the cathodic metals.
When two metals are placed with respect to one another, usually in a circuit, they create an electric field which causes the electrons to flow between the two metals. When the current flows between the two metals, a chemical reaction occurs and one of the metals becomes coated with a particular cathodic protection material. This coating acts like a shield protecting the cathodic protection from becoming corroded away.
Metal anodes used in cathodic protection systems can be made from several different alloys, which are typically soldered to a thin metal frame. Common cathodic protection structures include metal blocks with a layered finish or flat sheet metal. These structures are often referred to as “blocking sheets”. Various materials are employed for the flat sheet, such as aluminum, copper, tin, zinc, or steel. Block structures protect the two metals in complex configurations; however, these are less common. Larger structures such as polymer stack can also be used to provide protection against corrosion attacks.