That's an excellent and very specific question. Living near the ocean is wonderful, but the salt air is brutal on metals. For a trash can that won't rust, you need to move away from standard galvanized steel. Here are my top recommendations, focusing on material and construction.
First and foremost, look for Marine-Grade 304 or 316 Stainless Steel. This is the gold standard. The higher chromium and nickel content, especially in 316 (which contains molybdenum), provides exceptional resistance to saltwater corrosion. It will develop a patina but won't rust through. Ensure it has a satin or brushed finish; a mirror polish will show every scratch and water spot.
If stainless steel is beyond budget, consider high-density polyethylene (HDPE) plastic bins. Modern HDPE bins are incredibly durable, UV-stabilized to prevent fading, and completely immune to rust. Look for ones with metal components (like hinge pins or liner frames) that are also coated or stainless.
Another good option is heavy-duty powder-coated aluminum or steel. The key is the quality of the coating. A superior powder coat, properly applied over a prepared surface, creates a formidable barrier. For the best results, choose a product specifically rated for "coastal" or "marine" use.
Beyond material, consider design features: a tight-fitting lid to keep salt mist and rain out, secure fastenings to prevent lids from blowing away, and a dark color for the plastic or coating to minimize UV damage. Anchoring systems are also wise for windy shores.
My final piece of advice: avoid thin, painted metals or low-grade galvanized steel altogether. They will fail quickly. Investing in a quality marine-grade stainless steel or robust polymer bin from the start will save you money and hassle in the long run, keeping your coastline beautiful and functional.