Galvanised 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 galvanised 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, galvanised steel has its limitations in saltwater.
Galvanised steel used in oceanographic applications has both supporters and protesters. The Brookhaven National Laboratory notes that galvanised steel will rust rapidly in saltwater, necessitating replacement in a few months. However, the American Galvanizers Association states that galvanised steel will last about 12 years in saltwater, depending on placement.
Temperature has great effects on the zinc in galvanised steel. Seawater varies in temperature, and problems with galvanised 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.
In the tidal zone, or surface of seawater, zinc can erode from the galvanised steel, exposing the steel to saltwater. This is typically the reason for base steel corrosion.