Both electrodes protect the cathode metal. The metal used by the sacrificial anode is more active than the protected cathode metal and reacts itself. According to the principle of galvanic battery reaction, the metal of the more active metal electrode, namely the anode, is oxidized and lost. The auxiliary anode is made of inert materials, such as graphite, platinum, etc., and it does not react itself. According to the reaction principle of the electrolytic cell, the applied current is required for protection, and the anode is connected to the positive electrode of the power supply.