We just found a problem with some (translucent) speaker wire.

We have been tinning wires for a year by dipping the stripped end in no clean flux and then dipping again in lead free solder. We have a new customer that gave us translucent wires to tin and solder, one day after tinning the first batch we noticed that there was a greenish color for about 1/2" where we have tinned and soldered the wires.

Photo showing green discolouration of the wire

We follow the dipping procedure as directed in the flux PDF.

Has anyone seen this issue?

If it has happened before we did not notice because we were using colored wires.

  • 2
    \$\begingroup\$ A picture is worth a thousand words. \$\endgroup\$
    – DKNguyen
    Commented Nov 19, 2019 at 20:04
  • \$\begingroup\$ Do you have a sample of the colored wires from which you could remove the insulation to see if the same happens to them? \$\endgroup\$ Commented Nov 19, 2019 at 21:14
  • \$\begingroup\$ I do not have a picture of those wires but i did a test with some of the colored wires and it showed the same results after removing the insulation, also, it is not happening on all wires, some batches have more than others. \$\endgroup\$
    – Jose
    Commented Nov 19, 2019 at 21:23
  • \$\begingroup\$ Do you have a link to the "flux PDF"? \$\endgroup\$ Commented Nov 19, 2019 at 21:59
  • \$\begingroup\$ This is the PDF for the flux:kester.com/DesktopModules/Bring2mind/DMX/… \$\endgroup\$
    – Jose
    Commented Nov 19, 2019 at 22:59

1 Answer 1


According to Kester's "Green Corrosion with Rosin Flux?" https://www.kester.com/Portals/0/Documents/FAQs/GreenCorrosion_Global.pdf

The green is not an oxide. It is copper abietate. It is harmless but also green in colour like other harmful forms of copper corrosion.

It is formed when the abietic acid in the flux reacts with copper (particularly when heat-activated).

It is just the flux doing its job and reacting with the pre-existing oxides on the copper to remove them from the bulk copper surface to expose the clean copper below...except in this case it has nowhere to go and nothing to displace it (i.e solder). Copper that has no oxidation to begin with would not produce this green residue.

You can tell your customer this. It's nothing to be concerned about since it is not an actual corrosion product of copper.

Of course...unless it's due to chlorine released when PVC insulation is heated which might produce Coppper II Chloride (I'm not sure) which is also green but actually is an undesirable corrosive contaminant.

Either way, it doesn't seem like there is anything you can do about it other than not to dip the entire stripped end into flux. Even if you don't, it might wick up.

  • \$\begingroup\$ Hello, Thanks for the answer, we are not using rosin Flux, we use Kester Select-10 does that make a difference? \$\endgroup\$
    – Jose
    Commented Nov 19, 2019 at 20:23
  • \$\begingroup\$ @Jose The MSDS datasheet says it still contains rosin. All electronics rosins contain some kind acid anyways because that's how they remove the oxide layer. If it's not going to be one type of residue, it's going to be another. \$\endgroup\$
    – DKNguyen
    Commented Nov 19, 2019 at 20:29

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