SMALL - espritmodel.com SMALL - Telemetry SMALL - Radio
Reply
Thread Tools
Old Dec 19, 2008, 02:26 PM
Still Balsa Bashing
Cardiff, South Wales
Joined Aug 2006
134 Posts
Discussion
Black wire corrosion on a signal lead.

The title says it all.
Today I cut a servo lead with the intention of soldering an extension to it
I noticed the signal wire had a distinctive black discoloration to it, not dissimilar to “black wire corrosion”
The servo in question was a new Hitec 81.
It’s only ever plugged into to set up programme perimeters and horn centring before installation.
The servo is going back to the supplier for a replacement.

Just wondered if anyone else has come across this?

Martin
Mwin is offline Find More Posts by Mwin
Reply With Quote
Sign up now
to remove ads between posts
Old Dec 19, 2008, 03:53 PM
Proud to eat Kraut ;-)
Julez's Avatar
Germany
Joined Dec 2003
5,354 Posts
Partly.

Black wire corrosion happens in a multitude of situations. It is not dependant on any electric effect. Wires corrode on ground, positive, AC, DC, or lying unused in the store.

I attribute this effect to impurities in the copper, lubrication residue from the wire drawing process, acidic contents of the insulation, or interaction of said components.
Julez is offline Find More Posts by Julez
Reply With Quote
Old Dec 19, 2008, 04:56 PM
Registered User
Florida
Joined Aug 2004
4,155 Posts
Quote:
Originally Posted by Mwin
The title says it all.
Today I cut a servo lead with the intention of soldering an extension to it
I noticed the signal wire had a distinctive black discoloration to it, not dissimilar to “black wire corrosion”
The servo in question was a new Hitec 81.
It’s only ever plugged into to set up programme perimeters and horn centring before installation.
The servo is going back to the supplier for a replacement.

Just wondered if anyone else has come across this?

Martin
I doubt that this is true "black wire" but some other form of corrosion. Is the wire now very stiff and brittle? Will it take any solder if flux is used? Is there a bluish ting to the black? In some 45 years in electronics and RC, all the true "black wire corrosion" occurred only in the presence of NiCad batteries and then only if they were wet cells or dry cells that have had the safety pressure release activated. It also ALWAYS started at the battery terminal and slowly worked it way to the next connection or junction where it usually (but not always) stopped. If the wire is blue-black, brittle, won't solder under any condition, then it might be black wire disease. If all these conditions do not exist, then it is some other form of corrosion.
Rodney is offline Find More Posts by Rodney
Reply With Quote
Old Dec 20, 2008, 03:13 AM
Still Balsa Bashing
Cardiff, South Wales
Joined Aug 2006
134 Posts
Thanks Jules and Rodney for the replays.
I think your both correct it must be some impurities in the copper wire or the insulation.

The insulation was not brittle in any way and yes it would take solder. I did, however see some black spots on the surface after soldering.

I just hope this is a one off.

As a precaution the servo is not being used.

Martin
Mwin is offline Find More Posts by Mwin
Reply With Quote
Old Jan 14, 2009, 02:53 PM
Registered User
Tony Oliver's Avatar
North-East England
Joined Mar 2002
3,402 Posts
Black wire etc

I just selected one of my servo extension leads to shorten it slightly. Cut off the pins and got this:-

I've flown radio since the early 1960s and have come across this from time to time.

No prejudice here, my lead was brown, not black.
Tony Oliver is offline Find More Posts by Tony Oliver
Reply With Quote
Old Jan 14, 2009, 06:22 PM
Oxford Panic
AndyOne's Avatar
United Kingdom, Oxford
Joined Feb 2003
3,661 Posts
There's good evidence to suggest this kind of black-wire happens when you leave electronics in a damp storage area whilst there is a battery still connected but not necessarily switched on.

Tony, it's still on the negative wire though.

Andy.
AndyOne is offline Find More Posts by AndyOne
Reply With Quote
Old Jan 15, 2009, 04:17 AM
Registered User
Tony Oliver's Avatar
North-East England
Joined Mar 2002
3,402 Posts
Andy, all of the ones I've had go black are on the negative.
I rarely leave batteries in the models except where they are difficult to remove without disturbing servos etc. (usually slopers).
None of the corroded ones have been in those models, and all are kept in the house in warm and dry conditions too.
This one, for example was with all my other wires and extension leads in a plastic box which doesn't seal. It's with my cameras which need some careful storage too. I examined all the others but none had any sign of black.

A few years ago, after discovering a similar situation, I started to do a check over the winter of all my models for deterioration after a season's flying. I've replaced chafed wires, some plugs and sockets, mainly due to wear and tear,but no more of this blackening.
I remember commenting on this in earlier posts a few years ago.
It's just somthing which happens. Rare it would seem, but newcomers need to be aware of the possibility, but not get paranoid about it.
Tony Oliver is offline Find More Posts by Tony Oliver
Reply With Quote
Old Jan 16, 2009, 01:17 PM
Oxford Panic
AndyOne's Avatar
United Kingdom, Oxford
Joined Feb 2003
3,661 Posts
There seems to be more than one cause of black-wire but the moisture plus voltage one is known about so can be avoided. Other causes of corrosion still exist, one of which was postulated as incompatible conductor/insulation combination, or chemical breakdown of the PCV insulation. I have come across old PVC cable that has a definite odour of chlorine about it.

Andy.
AndyOne is offline Find More Posts by AndyOne
Reply With Quote
Old Jan 16, 2009, 01:57 PM
Registered User
Tony Oliver's Avatar
North-East England
Joined Mar 2002
3,402 Posts
You got it Andy.

PVC is polyvinylchloride - it does break down in time and can give off chlorine in some conditions. . I don't remember what's left, but it will undoubtedly be unpleasant, probably sticky and toxic to some extent.
Don't tell the PCGreenElfansafety lot!(although California's probably got 'em onto it already)
Tony Oliver is offline Find More Posts by Tony Oliver
Reply With Quote
Old Jan 17, 2009, 09:25 PM
Registered User
Quincy IL
Joined Jul 2006
522 Posts
I have been building and servicing radio systems since the mid 1960's.

I have had the "Black wire problem" in every color of wire ever used in RC systems.

I am not sure what causes it but my general impression is that some batches of PCV insulation but not all, cause this. Found many wire colors bad in some old Royal kit systems that passed through for repairs or check outs. Many more never had it and I have several Royal Tech and two Omega TX that never had it.

I recently upgraded one Omega TX with a HiTech Spectra TX module to FM and never found any problems with the old wiring.

JR appears to use silicon based insulation on their wires now and we have never found a problem with JR wiring nor have we seen any problems with the silicon wire on electric cars.

I don't think it is a quality problem as in RC manufactures using low cost wire as IIRC Boeing had the problem with 737 & 727 airframes wiring.

Hugh
Hugh P is offline Find More Posts by Hugh P
Reply With Quote
Old Jan 18, 2009, 04:38 PM
Proud to eat Kraut ;-)
Julez's Avatar
Germany
Joined Dec 2003
5,354 Posts
Thanks for your insider report.
Julez is offline Find More Posts by Julez
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Question Black Wire Corrosion PeterH Batteries and Chargers 0 Sep 15, 2008 06:22 PM
battery black wire corrosion tipperary Batteries and Chargers 6 Dec 01, 2005 06:53 PM
Question Black wire corrosion in TX yogorilla Radios 11 Feb 19, 2005 05:20 AM
Black (and Red, and White .. ) Wire Corrosion Bill Glover Power Systems 6 Sep 27, 2002 05:04 AM