OLD Spartan 2mm solid wire solder

[SteveNielsen]

I was given two unused spools of this still in little faded red and white boxes. No corrosion at all on the wire, looks brand new. It doesn't say what the alloy is. I can barely get it melting at 360c with a 2mm tip on my 70w iron. With my 100w gun it seemed to melt around 360c tip temp too. Any ideas?

[stj]

Re: OLD Spartan 2mm solid wire solder

sounds like plumbing solder.
if it is then it may be lead-free.
that would explain the melting point.

[SteveNielsen]

Re: OLD Spartan 2mm solid wire solder

Could be. I got it from my mom-in-law who used to have a boatload of craft supplies in her garage so I'm guessing it might also be craft solder. Since it is very old and shows no sign of corrosion I'm guessing it is lead free as well. I have a spool of pretty thick (1/16" dia) 60/40 solder that has gotten dull grey over time and I am pretty sure this stuff is much older than that and it shines like new.

edit - I have no intention of using it for electronic/electrical work, I am just curious of it's actual composition.

[eccerr0r]

Re: OLD Spartan 2mm solid wire solder

Melting point of lead is about 330C, maybe 100% lead? I'd see if I can get a more accurate melting point measurement...

[stj]

Re: OLD Spartan 2mm solid wire solder

it dont work that way,
more lead = lower melting point.
if it was 100% lead it would melt well below 170

[Th3_uN1Qu3]

Re: OLD Spartan 2mm solid wire solder

Yes it does. The lowest melting point lead/tin solder is the eutectic 63/37 with 183C. Lead alone or tin alone will have higher melting points. High lead solder (5Sn/95Pb) melts at 350C.

[eccerr0r]

Re: OLD Spartan 2mm solid wire solder

Melting points is weird (swiped from Wikipedia)

Pure Lead: 328 C
Pb90 Sn10: 270-302 C
"non electronic" PbSn 60/40: 183-242 C
50/50: 183-214 C
Electronic/Cheap PbSn 40/60: 183-189 C
Eutectic PbSn 37/63: 183 C
Pb5 Sn95: 238 C
Pure tin: 232 C

Something seems wrong the temperatures reported, though Wikipedia may be wrong too. However for sure that the melting point of any mixture of lead and tin should be lower than of pure lead.

That being said I have heard of 100% lead solder before and it's very possible. But lead is very dull gray so if it's shiny, it's probably not 100% lead.

Recently I've been working on my car's antifreeze and the Ethylene Glycol-Water mixture behaves similarly due to crystal formation interference. Water freezes at 0C, Pure Ethylene Glycol at -13C, but if you have a 30:70 mixture (the eutectic of water:ethylene glycol) the freezing point drops down to near -70C... Strange behavior? Nah, that's how it works...

[stj]

Re: OLD Spartan 2mm solid wire solder

i'v never seen pure lead solder - i suspect it would be too soft.
i'v seen pure lead bars - used for car bodywork.

[SteveNielsen]

Re: OLD Spartan 2mm solid wire solder

360c was the soldering tip temp measured with a type K probe when the solder melted. I understand having to get the tip much hotter than the melting point to get enough heat built up to override the heat-sinking properties of the rather thick (2mm) solder wire though. It wasn't meant as a particularly scientific measurement.