Why are zinc and magnesium often used as sacrificial anodes?

Zinc and magnesium are commonly employed as sacrificial anodes due to their ability to corrode preferentially to more noble metals such as aluminum and iron. In the process of cathodic protection, these less noble metals are strategically placed in environments where they may come into contact with steel structures, such as pipes or tanks. By corroding first, zinc and magnesium effectively protect the underlying metal from corrosion by taking on the oxidation process themselves.

This technique is crucial in water treatment and storage systems, as it extends the life of metallic structures that would otherwise suffer from rust and deterioration due to electrochemical reactions with moisture and other environmental factors. When zinc or magnesium corrode, they create a protective layer or consume the corrosive elements, thus safeguarding the integrity of the more valuable materials.