Michael Coslo wrote:
I have even considered an acid flux bath, followed by a long water
rinse, but that's always been verboten for electrical work.

FWIW, I "pickle" the heavily oxidized copper antenna
wire I have to solder by wrapping a paper-towel sheet
around the joint, pouring a tablespoon of "Lime Away"
on it, waiting half an hour and then unwrapping and
rinsing it throughly with tap water. The copper has
a reddish, 'blistered' look and soaks up solder like
a sponge. I make it a point to tin all of the "pickled"
copper on either side of the joint as well as the joint
itself.

The prohibition against using 'acid-core' solder on
electronics was that the acid flux was actually a solid,
would remain on the connection and be activated
by moisture later, eating away the connection and
the wires. The active acid in "Lime Away" is good
old sulfuric, which is washed away in this case by
liberal amounts of applied water or later rainfall.

Jim, K7JEB