Final answer:
To prevent the rusting of an iron pipe, magnesium can be used as a sacrificial electrode due to its more negative reduction potential, offering cathodic protection by corroding preferentially to iron.
Step-by-step explanation:
The metal that can be used as a sacrificial electrode to prevent the rusting of an iron pipe is magnesium. When a more active metal like magnesium is connected to an iron pipe, it acts as the anode in a galvanic cell, causing the iron pipe to act as the cathode. This prevents the iron pipe from rusting as the magnesium sacrificial electrode is easily oxidized in comparison.
To prevent the rusting of an iron pipe, a magnesium (Mg), zinc (Zn), or aluminum (Al) metal can be used as a sacrificial electrode. These materials act as anodes and corrode preferentially to iron when connected to the iron pipe, offering cathodic protection. Magnesium has a more negative reduction potential than iron, making it a very effective choice for a sacrificial electrode. As the magnesium corrodes, it protects the iron pipe by forcing it to act as a cathode, thus preventing its oxidation and subsequent rusting.