Humidity levels represent temperature and the amount of moisture that is in the air. Not all bodies of water have high humidity levels. For example, a lake does not always emit high humidity. However, the ocean as a churning and open body of water is prone to have its moisture lifted into the atmosphere and affect humidity. The constant exposure to high humidity and moisture contained in the ocean air creates a corrosive environment for items exposed to it.
The salt content of ocean water is a catalyst in the corrosive effect of moisture-dense ocean air. The salt content in ocean air is high, and when it is carried onto the shore in air streams it settles onto exposed objects and sticks. Salt coated objects repeatedly exposed to the elements are more prone to structural breakdown and corrosion.
Ocean air is driven by ever-changing currents. These currents are present in the ocean and also swirl the air above water. When combined, these forces act on the shore and on exposed objects. Imagine the gradual damage to your face if it were constantly exposed to strong moist wind currents. This kind of wind damage is similar to the corrosive damage in objects exposed to ocean air.
A final way that ocean air corrodes is when it is caught in mechanical parts that need air but do not respond well to moisture. For example, people who regularly drive near the ocean have problems with their radiators and air filtration systems. Radiators are cooled by a combination of antifreeze, water and air. Ocean air, with its salt molecules, can cause the filters to become clogged, corroded and ultimately inefficient.