Nightjar wrote:

I used a zinc chromate primer bought from a marine chandler and intended
for boat use. That was on new aluminium guttering in the 1980s. It is
still sound, but I don't recall the make this far down the line, even if
it is still made.

Probably International if it was for a boat.

http://www.mailspeedmarine.com/marin...ional%20Paints