How to predict copper wire discoloration defect

I would like to ask the forum is there any experience about procedure,system or instrument that able to predict possibility of discoloration on copper wire (any wire size).

In my case, we have experience about wire discoloration (due to oxidation, reddish and blackish color) after storage for several weeks. Even we already provide sufficient packaging, such as: plastic wrapping to cover all wire’s surface on bobbin, and following by carton cover. And for information, for every single wire bobbin, we conduct final check on wire surface condition to make sure there is no discoloration on wire surface and also to make sure that wire not in wet condition (wire wet condition may be happen due to application of water coolant/lubricant in drawing and annealing process and able to increase possibility of discolor defect).

But unfortunately, we have some complaint from our customer that they found discoloration problem at their site after several weeks in storage. (Note: is there anyone in this forum has information about maximum storage time before discoloration happened with proper packaging/cover?)

I do understand that discoloration problem comes from improper control on process parameter (especially annealing process). And we already took care about this matter. And as a Quality Assurance guys, we have to make sure that there is no NOT GOOD product (in this case: discoloration problem) goes to our customer. That’s why we need final early detection instrument/system. So, if anybody in this forum has related information, please do not mind to share your experience. Thanks in advance.

Discoloration can be due to several things. One is that the wire is not thoroughly cooled and as it sits, the heat from the inner part of the reel transfers to the outer part and the copper oxidizes.

Something else is residual wire drawing lubricants on the wire can cause discoloration.

Question that might affect the above is do you know if it takes a couple of weeks to discolor or are you waiting a couple of weeks to check it.

Thank you very much for uour reply/comment.

I agree with you that higher wire temperature affects on increase of discoloration risk. That is why in our factory we make some effort to control wire temperature come out from drawing process, especially for annealed wire.
But at this time we control wire temperature through controlling drawing lubricants/coolant temperature in range 45 - 55 oC.
(Please let me know whether this method correct or not. If not correct please give me advice)

About residual drawing lubricant, we already conducted some inspection about dryness/wetness of wire to minimize the risk.If we found wire in wet condition, we adjust flow of flushing air (by compressed air) to make sure all residual liquid on wire surface will flushed away.

Answering your last question: what I want is how to predict possibilities of copper wire to be discolor during storage by application of equipment/instrument.So, I want to know at a very recent time if my copper wire product will discolor in several weeks in the future along storage time.
So we can prevent a potential discolor-risk wire product release to customer. And I do not need waiting till customer complaint us about discoloration defect.
In my mind, I have imagination about such kind of instrument/equipment/chamber that able to simulate athmosphere condition where the copper wire kept( oxygen content in the air, humidity, temperature, etc.) which is promoting discoloration process but with speed up time. (We need no to keep the product for several weeks before releasing to our customer, but only in several hours or days)

In our case, discoloration mostly happened in outer part of reel/coil/loop of copper wire at bobbin packing. Discoloration risk become weaker in the inner part of coil/loop.

Waiting for your comment.

Best regards,

Your complaint is contrary to usual discoloration found in inner layers due to residual heat in the coil/bobbin. Since the problem is noticed more in outer layers, it points to some factor in your ambient...is there any hot gas or oxygen or chlorine emitting process being done around the bobbin storage area? Also are you cleaning your bobbins properly(with petrol or any organic solvent) before taking on the wire ?

naren kotecha