Coastal regions are some of the harshest environments for construction materials due to constant exposure to salty air, humidity, and prevailing winds. While many materials quickly deteriorate under these conditions, hot-dip galvanized (HDG) steel remains one of the most reliable solutions for long-term corrosion protection.
Why Coastal Climates Are Challenging
Salt-laden winds, marine spray, and high humidity accelerate the corrosion process. Structures located within one mile of the shoreline—especially within 250 feet—are exposed to aggressive chloride deposits that can drastically shorten the life of unprotected steel. Local microclimates further influence performance, with variables such as average temperature, rainfall, and wind direction playing a significant role.
HDG Steel in Practice
Research and field experience show that galvanized steel exposed directly to salty winds can begin showing rust within 5–7 years. However, sheltered areas of the same structure often continue to perform well for 15–25 years longer. Properly evaluating the environment during the design phase—including prevailing wind direction and whether the structure will benefit from natural rinsing by rainfall—is essential.
Enhancing Durability with Duplex Systems
For projects in aggressive coastal zones, a duplex system (paint or powder coating applied over galvanizing) can dramatically extend service life. When combined, the two protective layers often last more than 1.5 times the sum of their individual lives, providing decades of maintenance-free performance. Additional rinsing with potable water can also help, especially for sheltered structures that don't receive rainfall.
Best Practices for Specifiers
- Conduct a microenvironmental assessment for every coastal project.
- Position structures to minimize direct salt spray and maximize ventilation.
- Ensure proper drainage in the design to avoid water retention.
- Collaborate early with galvanizers and coating professionals if a duplex system is considered.
- Take precautions to prevent bimetallic corrosion when using HDG alongside other metals.
Although coastal environments accelerate corrosion for most construction materials, HDG steel remains a proven choice for long-lasting protection. With proper design considerations and, when needed, the addition of a duplex system, galvanized steel can provide reliable performance for decades—even in the harshest marine climates.
For a deeper dive into the original research and data that informed this article, see the American Galvanizers Association's article on HDG in Coastal Climates.
