The 5-colored wires's strands looks like aluminium, but it is basically copper wire at centre, with a thin conductive coating (my teacher shown it to me) of silvery-color, so that the copper doesn't get weathered .
If the rubbery insulator removed, and the metallic strands Scrapped with a knife or a shaving-blade, the silvery-colored layer removed, and the red, copper-interior comes out.
Now, i want to know, what substance(s) used in this coating?
These wires sold as 5-color electronic wire (for low voltages). I've given a scale also. Since nothing is printed on the insulator, and i buy in retail amount (1 or 2 yard) from a large spool, i've also no clue to the datasheet right now. (however, these wires are not very costly (around Rs. 10 per yard)).
The upper strands (with respect to photo) of the upper, yellow wire is scrapped with a blade and it shows red, coppery colour inside. the blue-one shown as reference or control.
Best Answer
What is it?
The coating is most likely tin plating.
The wire is similar to that used in Amphenol's Spectrastrip.
Figure 1. Amphenol's Spectrastrip.
Figure 2. The Spectrastrip datasheet lists the conductors as "tinned copper".
Why is it?
Figure 3. Despite severe oxidation her popularity remains untarnished.
Copper is a great conductor but is prone to corrosion - see the Statue of Liberty. Tin plating brings the following benefits:
But ...
Steve Lampen, Belden, in his blog post In Defense of Tinned Copper makes some very interesting observations.
In summary ...