How Saltwater Affects Corrosion on Galvanized Steel

Galvenized steel cables are often used in saltwater.

Galvanized steel is made up of two different kinds of metals to prevent the steel from corroding. Zinc is layered with the steel because zinc will not rust. It is said to be galvanized because the zinc literally becomes a part of the steel, not just layered on top of it like a sealer. Although praised for its use in marine environments, galvanized steel has its limitations in saltwater.

Differing Theories

Galvanized steel used in oceanographic applications has both supporters and protesters. The Brookhaven National Laboratory notes that galvanized steel will rust rapidly in saltwater, necessitating replacement in a few months. However, the American Galvanizers Association states that galvanized steel will last about 12 years in saltwater, depending on placement.

Sea Temperature

Temperature has great effects on the zinc in galvanized steel. Sea water varies in temperature, and problems with galvanized steel can arise when using it in warmer waters near the equator. This is because high temperatures cause zinc to degenerate, which leads to the steel being exposed to saltwater.

Tidal Zone

In the tidal zone, or surface of seawater, zinc can erode from the galvanized steel, exposing the steel to saltwater. This is typically the reason for base steel corrosion.

References

• Corrosion Doctors: Galvanizing
• Brookhaven National Laboratory: On Corrosion in a Marine Atmosphere
• American Galvanizers Association: Ask Dr. Galv