Protect coastal structures with galvanized steel to prevent corrosion and concrete damage.

By Pavan Kaushik

Who does not want to have a bungalow or flat facing sea. Globally, everyone wants to stay in room in a hotel that is facing sea-view. The mesmerising nature has its own depth like ocean which cannot be measured.

Coastal Environment and Building Damage

But not many know that the coastal environment causes severe damage to the building structure and envelope (i.e. exterior doors, windows, skylights, exterior wall coverings, soffits, roof systems, and attic vents).

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Corrosion and Concrete Deterioration

When steel reinforcement corrodes, the corrosion product occupies more than three times the volume of the original steel, exerting great disruptive tensile stress on the surrounding concrete, leading to further cracking, more weather access and further corrosion.

Effects of Corrosion on Concrete

In mild cases, rust staining occurs whereas in more serious cases severe spalling of concrete may occur and ultimately the concrete members may fail completely.

The Corrosive Impact of Coastal Moisture

The corrosive effect of salt-laden, wind-driven moisture in coastal areas cannot be overstated. Salt-laden, moist air can corrode exposed metal surfaces and penetrate any opening in the building.

Vulnerable Metal Connectors

Corrosion is most likely to attack metal connectors that are used to attach the parts of the structure to one another, such as floor joists to beams and connectors used in cross-bracing below the finished lowest floor.

Zinc Coating and Corrosion Rates

Galvanized connectors coated with Zinc at the rate of 0.9 ounce per square foot of surface area (designated G-90) can corrode in coastal environments at a rate of 0.1 to 0.3 millimeter/year. At this rate, the Zinc protection will be gone in 7 years.

Importance of Galvanized Protection

Alternatively, a G-185 coated connector, which provides twice as much protection as G-90, can corrode in less than 20 years. More galvanized protection (more ounces of Zinc per square foot of surface area to be protected) increases service life.

Factors Influencing Corrosion

Corrosion is commonly associated with deposition of sea salt in presence of moisture on steel and light metals. Chloride is the most significant corrosive species in the salt particles. Corrosion is influenced by the amount of salt on the metal surface and related to speed and direction of wind, distance of structure from the shore, elevation of the structures, degree of sheltering and frequency and amount of rain washing.