That's an excellent and very important question for any coastal area! Salt air is incredibly corrosive and can destroy ordinary materials surprisingly fast. Based on durability and maintenance, here’s how common materials hold up:
The top performer is Marine-Grade Stainless Steel (316 stainless). It contains molybdenum, which provides exceptional resistance to pitting and corrosion from chlorides (like salt). It's the gold standard for marine environments, though it is the most expensive option. It requires minimal upkeep.
A strong and cost-effective alternative is Heavily Galvanized Steel. The thick zinc coating acts as a sacrificial layer, protecting the underlying steel. Ensure the bin is galvanized *after* fabrication (hot-dip) so all welds and edges are protected. The coating will weather over time but offers long life.
Powder-Coated Aluminum is another great choice. Aluminum naturally forms a protective oxide layer, and a high-quality polyester powder coat adds an extra, durable barrier against salt and UV rays. It's lightweight and rust-proof.
Materials to Avoid near salt air include standard painted or mild steel (will rust quickly), and certain plastics which can become brittle and fade from intense UV exposure.
Final Recommendation: For maximum longevity with low maintenance, invest in marine-grade stainless steel. For the best value, choose hot-dip galvanized steel with a robust coating. Always ensure any bin has adequate drainage holes to prevent saltwater from pooling inside, which accelerates corrosion.