Silver solder flux

[DalboyParticipant @dalboy]

Still finding bits in the workshop anyway I found some silver solder of unknown quality which I intend just using to have some practice with, and will buy fresh and keep it marked for future reference.

Anyway down to the question about flux I have a full tub of Weldspares Silver Solder Flux which is in powder form and also very dry.

Is this still usable or does it have a shelf life like so many things.

Edited By Derek Lane 2 on 23/12/2018 18:31:41

[DalboyParticipant @dalboy]

[Thor 🇳🇴Participant @thor]

Hi Derek,

The oldest silver solder flux I have is over 30 years old, still works. So just try silver soldering a couple of leftover steel pieces together to see if your old flux still works.

Thor

[Chris TriceParticipant @christrice43267]

Your silver solder is likely to contain cadmium given it's age, which while potentially dangerous if over heated for a prolonged time, is still sought after in some quarters so worth keeping hold of. New cadmium free stuff is also quite expensive. As Thor suggests, just try the flux and see. It's highly likely it's OK.

[Speedy Builder5Participant @speedybuilder5]

Just be careful – if the silver solder is of the type used by refrigeration / air con engineers, its only OK for copper WHICH IS NOT FOR BOILER USE or even for STEEL. It looks a bit more coppery than the whiteish yellow of easy flo type silver solders.

If used on boilers, the steam erodes the joint. If used on steel, the joint looks good, but has no strength in it.

If you are doing boiler work get the proper stuff.

BobH

[DalboyParticipant @dalboy]

Thank you for the replies. The silver solder I got from a model engineers shows some time ago.

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