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I few days ago I cut and cap a copper pipe to start repairing an underground water leak in my garage. I noticed that the flux looked rather orange and when I solder a pipe the solder didn't flow very well. Yes the pipe was clean before and fluxed. I thought my soldering skills are rusty (they are) but if I applied more heat to the pipe, it didn't help. The flux and solder are about 15 years old. They've been sitting in my garage where it is not temperature controlled. I'm in S. California where it doesn't get really cold. It's been cold now and it is about 40F outside at night. The garage is closed but not insulated so it may get to the low 50s inside. In the summer it gets hot... around 90F maybe more. Is there something wrong with this old flux? or should I just buy a new kit (solder and flux)? Here is a picture of my flux and solder:

enter image description here

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    The solder isn't going to age. It's metal. The flux might. Jan 29, 2022 at 20:13
  • Huh. I have some ancient flux myself and it had partially crystallized into long needles. Still did what it was supposed to, though mine was meant for PCB soldering.
    – Ouroborus
    Jan 30, 2022 at 22:57
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    The pictured solder looks quite pristine, very unlike oxidized solder. Jan 31, 2022 at 13:33
  • Yes, but why not try a sample? Feb 2, 2022 at 21:03

4 Answers 4

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Yes, generally not a problem, most of my solder and flux is old enough to vote and/or drink and it's still fine. The flux, maybe if it's less stable than most, the solder definitely not a problem

I applied more heat to the pipe, it didn't help.

It's entirely possible to overheat a solder joint, at which point you have to stop, cool down, clean everything again, reflux and start over. If you burn the flux out of the joint, you'll never get it to go without re-cleaning. There's a narrow window between "not hot enough to melt solder" and "too hot" and it's common to head for the latter place when inexperienced.

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    I'll pick up some flux if I go to the store just to make myself feel better but I think the last sentence of your answer applies to me. Thanks.
    – Rodo
    Jan 29, 2022 at 21:54
  • Exactly my experience - I overheat the first joint after a 3-5 year lapse between episodes of plumbing, then remember how to do it.
    – grahamj42
    Jan 30, 2022 at 13:17
  • Yeah, when you don't do it very often it becomes very easy to goof, especially when you're working on existing pipes so you're in an awkward situation. Jan 31, 2022 at 1:59
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Of these two substances, solder (tin alloyed with small amounts of other metals like copper or lead if the solder is not lead-free) is chemically unable to "age".

Well, this is not absolutely true because tin is in theory able to oxidize in open air, but the process is both fairly slow (20 years are not decisive) and the metal will lose it's metallic luster and mechanical properties.

When subjected to extremely low temperatures (~ minus 40 deg. C or F) tin can convert into grayish dust that looks nowhere like tin but can still be used for soldering as it melts back into the normal, "metallic" form of tin.

On the other hand, some fluxes are pretty much able to age down into a substance unsuitable for soldering. This includes, but is not limited to, fluxes that pretend to be biodegradable, water-soluble, non-toxic or have other advanced properties.

Simple, traditional, 1-component solid fluxes like rosin/colophony or ammonium chloride are pretty much resistant to aging (at human-life timescale), while more complex, paste-like or liquid varieties may or may not be in good shape after 10 or 20 years.

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Doesn't apply to the reel of solder pictured, which is labelled "lead-free", but in the EU, the ban on solder containing lead came into force in July 2006, only just over 15 years ago - so solder that's "about" 15 years old may contain lead, with potentially deleterious health and legal consequences.

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    Doesn't apply because marked lead free. But also not EU - OP says "California'. Jan 31, 2022 at 2:02
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    @manassehkatz-Moving2Codidact though, as we Americans tend to say as a joke, everything causes cancer in California (the "joke" being that Proposition 65 warnings seem to appear on most products).
    – phyrfox
    Jan 31, 2022 at 13:02
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    Isn't ROHS specific to commercial electronics manufacturing, so quite unrelated to plumbing solder (to which, however, other regulations re: lead in potable water pipes might apply....)? Also, recent EU partial sales bans on lead solder (as opposed to banning the USE in newly manufactured electronics) are REACH, not ROHS related. Jan 31, 2022 at 13:37
  • @rackandboneman There was a lot of discussion in the British press in 2006 about whether it would apply to church organ pipes, but I never saw any actual conclusion to that discussion. Jan 31, 2022 at 20:09
  • That could actually be an interesting discussion, given there would be a possibility for perished/disintegrating solder to be blown airborne I guess... In the EU you should be able to buy it still if it is for commercial work or bought personally at a hardware store counter. No Idea (or care for) what Brexit made of it :) Feb 2, 2022 at 16:34
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Sounds lke most likely just over heated the joint. If possible, just take apart, reclean - flux & resweat the joint, Should be fine after that. Good luck with it.

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