【Daily Question】Theoretical Foundation 2020.09.07
Thread Content
Multiple-choice question: Which of the following methods for preventing metal corrosion is incorrect? ( ) (A) Applying paint to the metal surface; (B) In the method of impressed current protection, the metal to be protected is connected to the positive pole of the power supply; (C) In the method of impressed current protection, the metal to be protected is connected to the negative pole of the power supply; (D) To protect iron pipes, they can be connected to zinc sheets. Answer: B. Hint: Extra rewards will be given to those who can explain the solution process; the answer can be found in the response
(B) In the external current protection method, the metal to be protected is connected to the positive pole of the power supply;
The metal that holds B in place should be connected to the negative pole of the power supply. Sacrificial anode when connected to the positive electrode. Cathodic protection (electrochemical protection method) involves using a direct current power supply to make the metal to be protected act as a cathode; this method of protection is known as impressed current cathodic protection. This protection method, in which the metal to be protected is made the cathode by using an external anode (connected to a more reactive metal), is known as sacrificial anode cathodic protection.
B. In the impressed current protection method, the metal to be protected and another auxiliary electrode form an electrolytic cell. If the metal to be protected is connected to the negative pole of the power supply, it becomes the cathode of the electrolytic cell, where a reduction reaction occurs to protect the metal ； If connected to the positive pole of the power supply, the metal acts as the anode of the electrolytic cell, where it undergoes oxidation and is corroded