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When the surface of copper turns that greenish oxidized color, does the resistance to current flow increase or isn’t affected?
For instance if the point of contact is secure and clean but bare visible copper wire has oxidized will it still conduct electricity no problem?
Like this ground wire in my car. The resistance measured to the negative of the battery reads 0 ohms as well as from both ends of the cable itself. Which I suppose answers my question but I’m curious what others think. I’ve read the patina protects the copper from further corrosion so I’m starting to think it’s not a big deal.[IMG]http://uploads.tapatalk-cdn.com/20160610/cf160cf2f029fe05b2173df22541e754.jpg[/IMG]
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Yes it increases the wires resistance. The standard volt/ohm meter does not measure low resistances very well because the can not supply the higher currents needed, and would include the resistance of the meters probes. You really want to know the voltage drop across the wire when high currents are running through it (starter motor cranking, headlighs and accessories on, ect.)
So I measured directly across the battery and got a reading of 12.56v
Next I kept positive cable of meter on positive of battery and took random measurements from the cable in question to various metal parts of the car and reading was still 12.56v
You need to have high current flow through the wires, like if you are testing an ammeter.
Put the voltage probes across the ground wire, ans set the meter for millivolts. It should show zero voltage.
Crank the starter, which should put some current through the wire, and see if there is some voltage registered.Edit – The oxidized part is non-conductive and had eroded the copper slightly. I think the wire may also become more brittle.
Because the wire diameter has been eroded slightly, it will increase the wires resistance, but only a small amount.
The issue is if the erosion gets into the crimp, it will loosen and not provide a good contact.
I had a spade connector on the headlight circuit where the oxidization compromised the crimp. The headlights would work for about 10-minutes until the bad connection heated up and would loose contact, then no headlights. After some time, connection would cool and headlights would go back on for a few minutes, then repeat.[quote=”myfavecoupe_” post=167739] I’ve read the patina protects the copper from further corrosion so I’m starting to think it’s not a big deal.[/quote]
It’ll reach a point that oxygen has a difficult time reaching the copper beneath which dramatically slows oxidation, but any wire in an automobile will be long gone before that point.
A wire might put up with it for quit a while, but the stuff spreads like cancer. Once it reaches a PCB, the thin copper traces are toast.
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