5005 aluminium grade any good?

Could explain the absence of corrosion. Each new tide would simply wash away the localised charged electrolyte. Thus not enough time for corrosion to take place. A new tide every 12 hours I suspect is not enough time to initiate corrosion. Also considering considering non-marine alloys generally resist erosion better than marine grade alloys may also explain a bit too.

 

It seems remarkable all right. Was there any sign of marine grow as barnacles or oysters on that aluminium?
It might not be relevant to this thread but just to say, as I was sailing along the great barrier reef, about 15 years back , near Palm Island in north Queensland, I once past by a WW2 mine. The thing was adrift and looked brand new with no visible deterioration, no rust nor marine growth and as a new one it exploded on a beach north of Townsville a few days after.
I have no idea of the material the mine was build of, but we can say in those days they used excellent alloys.
cheers

 

Good old days when stuff was still produced at home, designed by good and rigorously trained engineers, made of tested and trusted materials, manufactured by people living a tough but fulfilled lives, who believed in value and importance of their job.

Than, at some point, "made in China" came along...