How come I have stripped back some wire and in a couple of days it starts to tarnish I know it’s a reaction with oxygen and the elements of the environment but a different brand when striped back hasn’t tarnished for months Is it a good thing that it tarnishes? Does that mean the copper is more pure and conductive?
Unfortunately copper wire is not made the same! The cheaper the cost of the wire, the less purity the copper is. I have had sample wire sent to me to test it by using a simple method of leaving it outside for a while. Just strip back some of the jacket to expose the bare copper wire and set it outside say on the back patio area on something and leave it there for a week or so. If you begin to see any greenish discoloration, then it is junk wire and should not be used for any audio connections.
Emile
Emile
Steve Eddy said:
Yes it is junk wire! Just get some copper wire made in china that may be 90-95% copper and the rest who knows what, and strip off the jacket/insulation and put it outside and see what happens! Then try the same thing with good copper wire. After both wires are done this way, you tell me which one you would use to connect a pair of speakers to your gear!
bzzt... wrong answer
Steve Eddy got it right...lousy insulation is the culprit. Corrosive byproducts leach over time and create an electrolyte that accelerates the corrosion. Wire purity has little to do with this form of corrosion.
Your "experiment" doesn't prove much of anything other than cheap wire has poor insulation
All copper corrodes in air, reacting first to form copper oxides, which then become hydrated and react to form copper carbonates of various compositions, hence the green coloring of copper roofs, capital domes, guttering, that sort of thing.
John L.
FSHZ:42 said:
Steve Eddy got it right...lousy insulation is the culprit. Corrosive byproducts leach over time and create an electrolyte that accelerates the corrosion. Wire purity has little to do with this form of corrosion.
Your "experiment" doesn't prove much of anything other than cheap wire has poor insulation
All copper corrodes in air, reacting first to form copper oxides, which then become hydrated and react to form copper carbonates of various compositions, hence the green coloring of copper roofs, capital domes, guttering, that sort of thing.
John L.
Back in the late 80's., when Monster cable was taking off and they were bragging about using OFC. A representative of Australia's largest producer of copper took some wind out of their sails by pointing out that all the copper they produced was oxygen free and of the same purity as that which was being touted as something special by Monster.
cheapskate said:
Aren't most of the impurities (of which oxygen is only one) or mechanical stresses introduced during the various steps of (less than fastidious) manufacturing process to convert raw copper (silver / or other alloy) ingots to wire (i.e. well before insulation or special "snake-oil" additives)?
How many wire companies actually draw their own wire, and under "ideal" conditions (whatever those might be)
I've seen 20+ year old speaker wire & interconnects marketed by Fulton, Naim, QED, Mogami, Prisma etc that look almost a good as new - insulation might be a bit stiffer than fresh, but strip back a few inches and the conductors are not corroded. OTOH, a 5 yr old run of cheap Canadian Tire zip- wire ("clear" plastic insulation) has already started to take on a nice patina that you often don't see on an old penny - so there's more likely some additional chemistry at play that can include leached insulator plasticizers and environmental variables.
cheapskate said:
That ain't exactly true.
Regular, ETP (Electrolytic Tough Pitch) copper does include oxygen in the atmosphere that it's melted in. The oxygen is intentional and is precisely controlled. Its purpose is to scavenge impurities within the copper and take them out of solution. By doing this, it improves the conductivity of the copper than if the impurities were left in suspension.
Oxygen free copper is melted in an atmosphere without oxygen. The actual purpose of oxygen free copper is to prevent the copper from becoming brittle if it's heated in a reducing atmosphere, such as hydrogen, which combines with the oxygen to form water vapor.
Because there's no oxygen to scavenge impurities, oxygen free copper is made to a higher purity in order for it to have the same conductivity as ETP copper.
As a side note, with regard to purity, a representative of Phelps Dodge once told me that all of their OFHC copper was made to 6N purity just as a matter of course and there was nothing special about it.
se
Devil's in the details
Actually, it's called ELECTROLYTIC TOUGH PITCH for a reason... it's made electrolytically... ..notwithstanding further processing during drawing, etc...
Knowledge Article from www.Key-to-Metals.com
Printable Version
Electrical coppers
Commercially pure copper is represented by UNS numbers C10100 to C13000. The various coppers within this group have different degrees of purity, and therefore different metal characteristics. Fire refined tough pitch copper C12500 is made by deoxidizing anode copper until the oxygen content has been lowered to the optimum value of 0.02 to 0.04%.
Electrolytic tough pitch copper C11000 is made from cathode copper - that is, copper that has been refined electrolytically. C11000 is the most common of all the electrical coppers. It has high electrical conductivity, in excess of 100% IACS. It has the same oxygen content as C 12500, but differs in sulfur content and in over-all purity. C11000 has less than 50 ppm total metallic impurities (including sulfur).
Oxygen-free coppers C10100 and C10200 are made by induction melting prime-quality cathode copper under nonoxidizing conditions produced by a granulated graphite bath covering and a protective reducing atmosphere that is low in hydrogen.
If resistance to softening at slightly elevated temperature is required, C11100 is often specified. This copper contains a small amount of cadmium, which raises the temperature at which recovery and recrystallization occurs.
High purity copper is a very soft metal. It is softest in its undeformed, single-crystal form, requiring a shear stress of only 3.9 MPa . Annealed tough pitch copper is almost as soft as high purity copper, but many of the copper alloys are much harder and stiffer, even in annealed tempers.
http://www.keytometals.com/Article27.htm
Steve Eddy said:
Actually, it's called ELECTROLYTIC TOUGH PITCH for a reason... it's made electrolytically...
..notwithstanding further processing during drawing, etc...Knowledge Article from www.Key-to-Metals.com
Printable Version
Electrical coppers
Commercially pure copper is represented by UNS numbers C10100 to C13000. The various coppers within this group have different degrees of purity, and therefore different metal characteristics. Fire refined tough pitch copper C12500 is made by deoxidizing anode copper until the oxygen content has been lowered to the optimum value of 0.02 to 0.04%.
Electrolytic tough pitch copper C11000 is made from cathode copper - that is, copper that has been refined electrolytically. C11000 is the most common of all the electrical coppers. It has high electrical conductivity, in excess of 100% IACS. It has the same oxygen content as C 12500, but differs in sulfur content and in over-all purity. C11000 has less than 50 ppm total metallic impurities (including sulfur).
Oxygen-free coppers C10100 and C10200 are made by induction melting prime-quality cathode copper under nonoxidizing conditions produced by a granulated graphite bath covering and a protective reducing atmosphere that is low in hydrogen.
If resistance to softening at slightly elevated temperature is required, C11100 is often specified. This copper contains a small amount of cadmium, which raises the temperature at which recovery and recrystallization occurs.
High purity copper is a very soft metal. It is softest in its undeformed, single-crystal form, requiring a shear stress of only 3.9 MPa . Annealed tough pitch copper is almost as soft as high purity copper, but many of the copper alloys are much harder and stiffer, even in annealed tempers.
http://www.keytometals.com/Article27.htm
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