Short answer: for most coastal cities, 316 marine-grade stainless steel with a powder-coated finish is the best all-round material for urban trash cans. It handles salt air, humidity, and frequent cleaning better than standard steel, and it still looks good in public spaces.
The key issue is chloride corrosion. Salt spray attacks ordinary carbon steel, and even galvanized steel can start rusting at scratches, welds, and hinges. 316 stainless steel contains molybdenum, which gives it much better resistance to salt and pitting. A powder-coated finish adds another layer of protection and lets the bin match local streetscape colors, but specify a marine-grade coating and treat cut edges properly.
Powder-coated galvanized steel is a practical budget option. It can last well if the coating is thick, welds are sealed, and the bins are rinsed and inspected regularly. However, in a coastal city, maintenance matters more: one deep scratch can become a rust pocket. HDPE plastic is another strong choice because it does not rust and is resistant to salt water, but cheap versions can fade or become brittle under UV. Choose UV-stabilized HDPE and sturdy metal inserts for moving parts.
For urban settings, also think about theft, vandalism, wind, and cleaning. Heavy bases, lockable liners, drainage holes, and non-corrosive fasteners matter as much as the body material. Avoid mixing stainless steel with plain steel bolts, because galvanic corrosion can ruin the joint.
So, if you want the best long-term performance, go with 316 stainless steel and a good powder coat. If budget is tight, use powder-coated galvanized steel with a real maintenance plan, or UV-stabilized HDPE for salt-heavy areas where rust is the main concern.