Final answer:
Cathodic protection is a method that reverses the electrical flow of corrosion, making the protected metal the cathode by using a more active metal as a sacrificial anode with the help of a salt bridge.
Step-by-step explanation:
The method that uses a current to reverse the standard electrical flow of corrosion and turns the corroding object into the cathode is known as cathodic protection. This technique involves the construction of an electrochemical cell by attaching a more active metal, such as magnesium or zinc, to the object needing protection. The more active metal becomes the anode with a more negative reduction potential, and the protected metal becomes the cathode. A salt bridge, such as seawater or ground water, completes the circuit, allowing oxidation to occur at the anode, thus sparing the cathode from corrosion. For example, a magnesium rod (Eº = −2.37 V) can be used to protect an underground steel pipeline, with the soil acting as a salt bridge.Galvanic cells, with anodic and cathodic sites, lead to the process of corrosion in materials like iron and silver. Strategies to counteract this include galvanization and the use of sacrificial anodes which is essentially cathodic protection. Frequently, this method is applied to protect the hulls of steel ships or underground pipes from rusting.