I've had aluminum flashing on my place about a quarter-mile from the beach for around 7 years, and it's held up pretty well. Definitely better than the galvanized stuff I replaced before it, which was already starting to rust and pit after just a couple years. Aluminum does get a bit chalky-looking over time, but honestly, that's more aesthetic than structural. Haven't noticed any real weakness or brittleness yet.
Copper looks great when it's new, but man...it turns greenish-brown pretty quick near the ocean. A neighbor down the street has copper flashing and gutters, and after about 3-4 years it went from shiny penny to Statue of Liberty vibes. Some people love that look—others not so much, haha. Plus, like you said, it's pricey as hell.
Honestly, marine-grade stainless or aluminum seems like the sweet spot between cost and performance if you're dealing with salty air regularly. Just my two cents based on experience (and a little trial-and-error).
Have you considered zinc flashing at all? Aluminum is definitely solid, but I've seen some coastal homes with zinc flashing that seem to hold up impressively well. It develops a patina similar to copper, but the color change is more subtle—more of a matte gray rather than that intense green look copper gets. Plus, zinc tends to self-heal minor scratches or dings over time, which is handy in harsh conditions.
I do wonder though, have you noticed any corrosion around fasteners or joints on your aluminum? Even marine-grade aluminum can sometimes react with dissimilar metals (like steel screws or nails), especially in salty air. Stainless steel fasteners can help, but they're not always standard construction practice, unfortunately.
Anyway, just thought I'd throw zinc out there as another option worth looking into—might hit that sweet spot you're after between durability, aesthetics, and cost.
We actually looked into zinc flashing when we first moved in, but the contractor steered us toward aluminum because of cost. Haven't noticed major corrosion yet, but now you've got me worried about those fasteners...might have to climb up and double-check this weekend.
Aluminum flashing is pretty common near the coast because of cost, but you're right to double-check those fasteners. If they're standard galvanized steel, they can definitely corrode faster in salty air. Stainless steel fasteners (316 grade ideally) are usually the safest bet. I swapped mine out after noticing rust streaks running down from the screws—caught it early enough to avoid bigger issues. Worth the hassle to inspect them now rather than deal with leaks later...
Good advice about the fasteners, but don't overlook the flashing itself either. Aluminum's cheap and easy, but I've found it can develop pitting and corrosion spots pretty quickly near salty air. Had to replace some sections a few years back because they were starting to crumble in spots. If you're near the ocean, copper flashing is pricier but holds up way better over time. Just something else to think about while you're up there swapping screws...
