What is a typical example of a sacrificial metal used in CP?

• A. Copper is the primary sacrificial metal for buried pipelines.
• B. Zinc is commonly used for steel in buried or submerged structures; magnesium or aluminum may be used in specialized cases.
• C. Iron is commonly used as sacrificial anode.
• D. Tin is used for all CP applications.

Answer: (B)

Cathodic protection works by using a metal that is more electrochemically active than the structure being protected to act as the sacrificial anode. For steel in buried or submerged conditions, zinc is the typical sacrificial anode because it readily corrodes in preference to steel, providing the necessary protective current at a reasonable cost. In specialized situations, magnesium or aluminum can be used as sacrificial anodes when higher current demand or specific environmental conditions are present. Copper isn’t chosen as a sacrificial anode for buried pipelines, iron would simply corrode itself as the anode, and tin isn’t used for CP in general.