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Flux, or something stronger?

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Willbe

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Old stranded lamp cord is very hard to solder, due to tarnish or a layer of oxide.
Anybody have a recommendation for a chemical, in the form of liquid or paste, that would help the solder wet the copper?
 
Old stranded lamp cord is very hard to solder, due to tarnish or a layer of oxide.
Anybody have a recommendation for a chemical, in the form of liquid or paste, that would help the solder wet the copper?
I found liquid soldering flux to be a great aid in soldering oxidized PCB pads. But if this is used for AC maybe you should not be soldering it.
 
Old stranded lamp cord is very hard to solder, due to tarnish or a layer of oxide.
Anybody have a recommendation for a chemical, in the form of liquid or paste, that would help the solder wet the copper?

Sometimes one has to mechanically scrape.

They make wire scrapers for this, e.g. for taking the varnish off enameled magnet wire, cleaning up oxidized resistors, leads, and stranded cord :)
 
Think you hit the nail on the head here, this is usually the issue.

Since the flux (acid) can't penetrate the sealer, you get no cleaning effect, really all flux does.

-BaC
Sometimes one has to mechanically scrape.

They make wire scrapers for this, e.g. for taking the varnish off enameled magnet wire, cleaning up oxidized resistors, leads, and stranded cord :)
 
Normally I just carefully scrape it with a knife or something. But if you really want it clean let it soak in a little salt and vinegar for awhile; add some flour if you would like it in a paste form. You could also use Tabasco sauce (contains salt and vinegar). Be sure to rinse it off when you are done to remove the salt and acid or it will corrode over time. You also need to make sure water that wicks up into the cord is dried out.

When the wire is ready be sure to use flux when you solder. Use heat shrink (not tape) to insulate the joints from each other and another piece over the whole joint.

My best solution is to replace the lamp cord; it is not really that expensive.

Dale
 
Normally I just carefully scrape it with a knife or something. My best solution is to replace the lamp cord; it is not really that expensive.

Right, scraping with a knife works just fine. We've all done that. However, the scraper I was referring to does two sides at once and speeds things up. But a folding electricians' type knife works just fine...

(I presume the OP has some good reason for asking about his old cord, right OP? Like it's something difficult to replace, hard to get to, right? It had better be... :) )
 
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Old stranded lamp cord is very hard to solder, due to tarnish or a layer of oxide.
Anybody have a recommendation for a chemical, in the form of liquid or paste, that would help the solder wet the copper?

Do you have any HCl? :)
 
The OP was about lamp cord. 2 conductor stranded wire. On the stuff I have worked with the strands were bare copper.

Right.

DSGargia and I presumed Willbe had a good reason to ask for help here as lamp cord is easier and cheaper to replace than mucking with his hard-to-solder old cord, unless it was hard to replace, or had some sort of sentimental value, etc.
 
hi,
I have a small tin of Plumbers soldering paste which I use for these corroded
solder jobs, it works every time.
A small tin of paste will last for years, my tin is over 30 years old.!

Its quite aggressive, so after tinning the joint should be well cleaned, with soapy water or meths is good enough.

I wouldnt recommend it for pcb work.

Useful for retinning those wearing solder iron points/tips, clean the tip after tinning.
 
Sometimes one has to mechanically scrape.

They make wire scrapers for this, e.g. for taking the varnish off enameled magnet wire, cleaning up oxidized resistors, leads, and stranded cord :)
You have a manufacturer name? I've never heard of this.

I ended up using fine sandpaper, but I think brush bristles would be better. It was one of these 50w hanging lamps using an electronic xformer upstream. These things are awful to troubleshoot.

With the chemicals I'd be concerned it would wick up into the insulation, so I was wondering if anybody made a fast-evaporating mild acid that would do this. I e-mailed some manus about this, but no answer so far.
 
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You have a manufacturer name? I've never heard of this.

Sorry, no. These were big in Germany (where/when I made my own 30 years ago), but haven't really looked for them as I already have one. Those Germans are sort of sneaky, they have all sorts of little gizmos that I rarely see here. But here's a quick drawing depicting what I'm talking about (mine is stainless steel):
 

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Vinegar is a weak acid.
 
so I was wondering if anybody made a fast-evaporating mild acid that would do this.

Aromatic solvents evaporate quickly, but I don't know of any acid that does. Muriatic acid is diluted HCl (about 30%) and is easily obtainable (as pool acid). I'd try the acid-based flux as has been pointed out, or scrape (or perhaps even cut the wire back a bit, although when it's this far gone, most of it is)...
 
You will have to take precautions against excessive damage,but here goes:
Dilute some ferric chloride etchant about 4 to1 and dip. watch the progress carefully or the wire will be all gone.
A teaspoonful of battery acid and a pinch of saltpeter, as above, do it outside, nasty fumes.
(This line deleted, liable to explode)
Wash well with water after these options.
This one works brilliantly on enamelled copper, and is a really good cure for litz wire: Pour a small quantity of methylated spirit into a metal bottle cap and light it. Burn the wire in the flame, and dip it in the liquid spirit while still red hot. Repeat if needed.
Go to your music shop and get some rosin. Put it in a thick plastic bag and powder it carefully with a hammer( it's horribly sticky) Now dissolve it in isopropyl alcohol or methylated spirit. I find a thick syrup the best consistency. Dip the wire in and solder it.
 
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When I put new ends on my cars battery cables I soldered the stranded cable to keep it from corroding. The "must wash" liquid flux pen that I use on nasty PCBs did the job. And yes it took a lot of heat.
 
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