Can I still use this old (15yrs) flux and solder?

Question

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:

Answer 1

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.

Answer 2

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.

Answer 3

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.

Answer 4

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.

Answer 5

Old flux may not work properly. Oatey claims shelf life of their flux is "2 years from date of manufacture." This statement can also be found in PDF data about particular flux, but it may not be on the flux container.

I just had a failure due to Oatey No 95 tinning flux that was about 9.5 years old. It left flux inclusions in the joint that caused a leak. When I tested it on the outside of a small section of pipe, flux from the top of the container left black clumps instead of tinning the pipe. Solder applied on top of it stayed in a small area and did not flow well. When dug deeper in the container and used some flux from there, it seemed to work fine. The pipe turned silver where it was covered by flux, and solder I applied to it flowed easily. So, there is still some usable flux in the container, but there is no sure way to tell what flux is bad, and I don't want to risk it.

Tinning flux probably goes bad more quickly because flux can chemically react with the metals contained in it. I've also read about water soluble flux going bad. Maybe non water soluble flux like Oatey No 5 can last a longer time, but even Oatey's technical specification for No 5 flux says shelf life is 2 years from manufacture date.

Joints that fail immediately can mean a lot of extra work, and later failure can be very costly due to water damage. Because of that, I think it makes sense to use fresh flux for plumbing work.