On 16 Jul, 20:58, Thomas Prufer
wrote:

One more option, since it's galvanised, is to put a blob of solder on the zinc.

If it were still galvanised, it wouldn't have a hole in it. I assume
this is actually a rusty margin and would be a pain to try and solder
to. If you do try it, use Baker's Fluid as a flux rather than hoping
resin multi-core will work.