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Metal is protected using the principle of galvanic cells, with efforts being made to eliminate the galvanic cell reactions that cause electrochemical corrosion. Electrochemical protection methods are divided into two main categories: anodic protection and cathodic protection, with cathodic protection being the more widely used method. Sacrificial anode protection: In this method, a more reactive metal (such as zinc or alloys of zinc) is connected to the metal that is to be protected. When electrochemical corrosion occurs, this reactive metal acts as the negative electrode and undergoes oxidation, thereby reducing or preventing corrosion of the metal being protected. This method is often used to protect steel piles and ship hulls in water; for example, to protect steel water gates, several zinc plates are welded to the part of the ship’s hull below the waterline or to the rudder near the propeller, in order to prevent corrosion of the hull and other components. External current protection involves connecting the metal to be protected to the negative pole of the power supply, while another conductive inert material is connected to the positive pole of the power supply. When energized, it causes an accumulation of negative charges (electrons) on the metal surface, thereby preventing the metal from losing electrons and achieving a protective effect. This method is mainly used to prevent metal equipment in soil, seawater, and river water from corroding. Another method of electrochemical protection is called anodic protection, which involves applying an external voltage to cause the anode to become passivated within a certain potential range. It can effectively inhibit or prevent metal equipment from corroding in acids, alkalis, and salts.