CLIMATES NOT TO USE COR-TEN®:
COR-TEN® steel requires alternating wet and dry cycles to form a properly adhered protective layer. Areas that have salt laden air, high rainfall, humidity, or persistent fog are typically not the proper environment for COR-TEN®.
The new bridge is made of marine-grade aluminum.
[1] http://www.hmbreview.com/news/groundbreaking-for-coastal-tra...
Galvanization was popular for a brief time while the industry was still trying to find replacements for lead in paint that didn't have crap performance.
Cold galvanization is expensive and involves nasty chemicals. Hot galvanization is cheaper but not as cheap as paint and involves equally nasty chemicals and molten metals.
Basically paint is cheap and good enough.