First I wrote: You need to etch off the zinc with some acid first.
Then your solder
will stick. Tom


Then Chris wrote: T'other way around. Zinc solders quite nicely.
Steel does not (or
at least not with plumbing solder). The issue is whether you can clean

the zinc coating well enough to solder to without scratching off so
much
zinc you can't get a full seal.


You're absolutely right. Thanks. Tom