# Reasons not to use bare copper wire in your car



## t3sn4f2 (Jan 3, 2007)

I know this has been talked about a little before, but its definitely worth bringing up again.

http://www.cast-lighting.com/art-tin-coat.html

The is a quote from the above link which is for lamp wiring, same thing as wire in your trunk basically.

" 1. All outdoor wire is subject to 'wicking'. This is the migration of water and electrolytes under wire insulation. This moisture travels from wherever the wire has been cut including splice points, socket connections and transformer terminals. Wicking causes a progressive oxidative corrosion of the wire.

The wicking problem has long been recognized by marine engineers since moisture is constantly present in the marine environment. These engineers, working in concert with regulatory and advisory agencies, developed marine-grade standards for boat wiring. These standards require tin-coated copper wire. (UL 1309 and 1426)

The presence of moisture in the landscape makes outdoor lighting wiring more akin to marine applications than to wiring used in the low-moisture indoor environment. For this reason, CAST has adopted the Marine-Grade standard by introducing No-Ox tin-coated wire.

*2. Oxidative corrosion of copper and its effect on conductivity. Electrical conductivity is a measure of a materials ability to carry an electrical current. Copper is an excellent conductor making it ideal in all electrical applications. However, in the presence of air and moisture its surface oxidizes forming a layer of copper oxides that conduct electricity very poorly. This layer is not initially a problem since the layer is very thin and actually serves to protect the underlying copper.*

*In an outdoor corrosive environment, however, the oxide layer progressively extends deeper into the copper strand and eventually oxidizes the entire thickness. The resultant decrease in conductivity severely compromises the lighting system. Landscape lighting wire is especially prone to this severe corrosion because it is a stranded wire with very thin strands. Lighting installers often see the devastation of this effect when they pull old wire from the ground and see the strands completely blackened and brittle.
*
Tin-coating the wire protects from this type of progressive corrosion and loss of conductivity in two ways.

*1. Sacrificial. The tin coating differs in electrical potential from copper in a way that causes the tin to be oxidized in preference to the copper. In other words, instead of a progressive deepening of the corrosion into the strand, the tin must completely oxidize before the copper interior is subject to corrosion.*

*2. Greater Conductivity of Tin Oxides. While copper oxides are very poor electrical conductors, tin oxides maintain good conductivity. This benefits the long-term conductivity of the entire wire bundle. Note: the initial conductivity of the tin coating is lower than copper, leading to a slightly higher voltage loss at time of installation. This difference is offset over time since the tin coating largely maintains its conductivity while the oxidized copper conductivity significantly decreases over time.
*
Solderability – Differences between Tin and Copper. Landscape lighting installers use a variety of methods for making wire connections in the field. Of these methods, soldering provides the most secure, corrosion-resistant splice points. CAST teaches this soldering method at all its seminars and workshops.

Since tin solder is the preferred type, it stands to reason that tin-coated wire is the best recipient of this solder. The resultant connection provides a seamless surface of tin that extends from the solder point along the entire length of the wire.

This is critical for corrosion prevention since corrosion occurs most aggressively when two dissimilar metals are in contact with each other and exposed to the environment. A tin solder connection on an all-copper wire is an invitation for corrosion to occur at the copper-tin boundary.

Soldering can be especially problematic when old wire is soldered. This situation occurs frequently since installers are often called upon to add fixtures to an existing system. Tin-coated wire maintains good solderabilty as it oxidizes over time. Copper oxides, on the other hand, are extremely resistant to solder.

An installer trying to add new fixtures to a system with all-copper wire, may be forced to replace entire wire runs while a system with tin-coated wire may be cut and re-soldered to make the new connections."


As far as I see it, tinned wire is the only way to go on any wire for your system. Not even properly terminated (solder with gold ends or professionally crimped) copper wire will work due to the "wicking" mentioned above, the ends will be fine but where the insulation was compromised will be an area that will start to corrode and eventually fail.


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## invecs (Jul 30, 2005)

Yup. I've been using tinned copper wire for years...and I don't hear any sound degradation. Checkout Supra ply wires...those are tinned copper wires with low inductance.


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## zero7404 (Jan 31, 2008)

i would think that any kind of higher-end car audio manufacturer that sells wiring kits would have done the research before they sell to the masses.

i went with audison for amp, speaker and rca wire. hopefully they won't degrade in the next few years.


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## t3sn4f2 (Jan 3, 2007)

zero7404 said:


> *i would think that any kind of higher-end car audio manufacturer that sells wiring kits would have done the research before they sell to the masses.*
> 
> i went with audison for amp, speaker and rca wire. hopefully they won't degrade in the next few years.


Hehe, why would they do that? Only reason to look after things like this is when you have warranty on that item or when its a safety issue.


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## jp88 (Jun 25, 2007)

I am a marine electrician by trade and can tell you first hand that there is a HUGE difference in the lifespan of tinned copper wire and bare copper wire in a marine application. The use of heat shrinkable connectors or heat shrink over regular crimp connectors helps a lot as well.

joe


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## phatredpt (Feb 22, 2006)

Now I won't dispute tinned copper being superior as far as corrosion resistance at all...
However, in an automotive environment bare copper is not as huge of a problem as it would be in landscape lighting IMHO. 

Landscape lighting is usually buried in soil which is damp most of the time (especially with irrigation, mulch, and fertilizer containing corrosive salts) and is usually connected in a daisy chain fashion which means it has insulation breaks all along it's length. Not very equivalent to what we do with car audio really.

SAE SGT spec cable which has been a spec standard for power and ground cable on automobiles for decades is in fact bare copper with a PVC insulation rated at 105 degrees C. This is much more exposed to the elements than audio equipment would be.
Crimping terminals properly creates a vapor tight interface between metals, and soldering correctly also creates a barrier to oxidation at the interface. If you have enough moisture to have wicking of moisture into the wire stranding under the insulation to actually degrade the copper beyond the surface I would think you would have some other issues going on with your electronics as well.

Now again... I am not knocking using tinned wire FTW whenever possible, but as frequently as installs get swapped around here and since for the most part we are talking about an environment that is usually considered "dry", if bare copper is what you have on hand you will probably be able to "get by" without disaster for a few months...


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## phatredpt (Feb 22, 2006)

I should add....
I am an engineer for an OEM that manufactures equipment that dispenses insecticide (nasty ass corrosive) and we use both tinned and bare copper wire in the construction of our machines.
In my 20+ years I can honestly say that I have not seen a HUGE difference in the lifespan of either.
They both fail EVENTUALLY (years)


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## zero7404 (Jan 31, 2008)

i should add too....

i'm an aerospace engineer working for a company that makes thrust reversers for commercial aircraft. don't get too much into wiring except to lay out schematics & runs in CATIA. but i can tell you those harnesses are tighter than tight and cost a ton of money to develop. whatever wire cores used on aircraft applications should be suitable for automotive use.


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## t3sn4f2 (Jan 3, 2007)

phatredpt said:


> Now I won't dispute tinned copper being superior as far as corrosion resistance at all...
> However, in an automotive environment bare copper is not as huge of a problem as it would be in landscape lighting IMHO.
> 
> Landscape lighting is usually buried in soil which is damp most of the time (especially with irrigation, mulch, and fertilizer containing corrosive salts) and is usually connected in a daisy chain fashion which means it has insulation breaks all along it's length. Not very equivalent to what we do with car audio really.
> ...


I really don't think its any where near dry. Humid hot car doors, leaky trunks, puddle soaked engine bays. Add to that an average joes lack of knowledge and tools to do a proper crimp the way the factory can. I think the majority of people don't switch out stuff monthly and don't want to get by for a few month after they install something, besides its not so much more expensive that it would be considered an upgrade and not a standard. 

Now if you can't afford to do it the right way and need to get by, sure its not going to fail the next day. Just don't go buying some thousand dollar amps and use plain copper on them you know.


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## phatredpt (Feb 22, 2006)

zero7404 said:


> i should add too....
> 
> i'm an aerospace engineer working for a company that makes thrust reversers for commercial aircraft. don't get too much into wiring except to lay out schematics & runs in CATIA. but i can tell you those harnesses are tighter than tight and cost a ton of money to develop. whatever wire cores used on aircraft applications should be suitable for automotive use.


Probably Tefzel or Teflon insulation and depending on the temp either tinned copper, silver plated copper, or high temp apps use Kynar insulation and silver alloy, or platinum conductors.

Teflon is limited use now days in general aircraft wiring since it tends to "split" lengthwise with stress and was linked to some problems.
Amazingly PVC insulation is accepted now since it is not nearly as toxic in case of an aircraft fire and is considered self extinguishing.
It is out of concern for the abilty of the pilot to live long enough to land the thing! 

( We do some aircraft equipment also )


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## phatredpt (Feb 22, 2006)

t3sn4f2 said:


> I really don't think its any where near dry. Humid hot car doors, leaky trunks, puddle soaked engine bays. Add to that an average joes lack of knowledge and tools to do a proper crimp the way the factory can. I think the majority of people don't switch out stuff monthly and don't want to get by for a few month after they install something, besides its not so much more expensive that it would be considered an upgrade and not a standard.
> 
> Now if you can't afford to do it the right way and need to get by, sure its not going to fail the next day. Just don't go buying some thousand dollar amps and use plain copper on them you know.


Oh I wasn't disagreeing with you at all!
Tinned copper is not much if any more expensive and if you are purchasing I would definitely go for it.  
As a matter of fact if I am running thousands of $$ in amps I would probably go for some higher end wiring, paying attention to other factors as well.  
(not the silly stuff that claims to sound "warmer" at $25 a foot either.. I don't want to EQ with wire!)  

I was just saying the landscape wire application notes are a little extreme...

The real problem is some of what is sold as Car audio wire is JUNK!


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