The wood we recommend for a project like this is teak (this is because it's not susceptible to fungus). You'll want to use silicone around all the edges of the shelf to seal it and protect the bracket as well.
Aluminum does corrode over time, but it takes quite a while. The aluminum we use for our Hovr brackets is 6063 T6, and has a corrosion factor of 3 (5 being the worst, 1 being the best) - this is because it is alloyed with silicone and magnesium. You can learn more about aluminum cast and wrought alloys in this very informative article here:
https://www.thomasnet.com/articles/metals-metal-products/types-of-aluminum/
You will also obviously need to seal and protect your shelf material from water as needed. Aside from that, this is no problem at all!