Answer :
Final answer:
Copper tubing used underground must have a cathodic protection system installed at the tank to prevent corrosion through the use of a sacrificial anode, like magnesium or zinc.
Explanation:
When coated copper tubing is used underground, such as for delivering gas from a storage tank, it must have cathodic protection installed at the tank. This system helps prevent corrosion of the metal due to electrochemical reactions occurring underground. In the process of cathodic protection, a more active metal, such as magnesium or zinc, is connected to the copper tubing. The active metal, known as the sacrificial anode, is more easily oxidized than the copper and corrodes first, which protects the tubing by acting as a barrier to corrosion. The protective measure ensures the longevity and safety of the underground systems. The soil between the sacrificial anode and the cathode (the tubing) acts as a salt bridge, completing the electrical circuit necessary for the cathodic protection to be effective.
