How durable are the aluminum radiators vs. the copper/brass types, especially in a coastal area with a lot of salt in the air?

How durable are the aluminum radiators vs. the copper/brass types, especially in a coastal area with a lot of salt in the air?

That really depends on how well they are taken of.
An aluminum radiator is as strong and sometimes stronger. I have had bricks hit mine. One held a rail car together after welds broke. The tank were stretched, but it never leaked. Also, aluminum does not become brittle like copper. AS said in another post, the only problems I have had is caustic agents especially residue from the dip tank when the engine is built. One would want to keep dirt or salt rinsed out of the radiator, and change coolant at least every 2 years. Also be sure all body to engine grounds are good and use distilled water to eliminate electrolysis.
Short answer, One sould expect at least 10 years with reasonable maintenance.