Sacrificial Protection

Zinc is more electrically active than steel. By coating steel with zinc, or a zinc-rich product, the zinc becomes the anode for the steel. The steel then becomes the cathode and does not react with the electrolyte. The process is known as cathodic protection.

This protective effect occurs even when there is a small area of steel exposed directly to the electrolyte, such as a cut sheet edge, drill hole or scratch.

While the zinc reacts in preference to the steel, it does so at a slower rate. In normal environmental conditions, the zinc-oxide layer that initially forms on the surface of the zinc combines with carbon dioxide in the atmosphere to form zinc carbonate. That creates a sealed layer with excellent adhesion, and as zinc carbonate has very low solubility, reaction with the electrolyte slows even more.