Aluminum

Perhaps I should have posted here instead of the metal boatbuilding section. In any event apologies for any indescretions. Cutting and pasting from my other post:

I am hoping someone can give me a little bit input about the different aluminum alloys that could be used in a marine environment. I am aware that the 5000 series is the generally considered best.

It was my understanding that this was a corrosion issue. It has recently been brought to my attention that perhaps it is the difference in strength etc. I have some upcoming aluminum fabrication, most rail and antenna mounts. The sizes and thicknesses make me think the 6000 series would be good enough. It certainly is cheaper and easier to source.

Thanks in advance for anyone shedding a bit of illumination on this for me.