Question about assembling my own DIY AC Cable

If you use copper as a base metal in a connector I can guarantee you it's not pure, and that's just fine.

Don’t overthink it. No need to know the molecular breakdown here. Use good connectors and you’ll be fine. 
I suggest contact enhancer mainly to prevent oxidation on bare wires over time from the remnants of oils left from your fingers. Deoxit will do as well. 

I agree with @audphile1 @erik_squires ​​​​@jea48 - don’t overthink it.

You are almost surely plugging the plug into a wall receptacle or power conditioner with brass, phosphor bronze, or beryllium copper contacts, and depending on what was used in your amplifier, you are probably plugging the IEC into an inlet with one of those same materials, unless either the designer used a higher level Furutech IEC inlet or you upgraded it. Furutech apparently uses copper connectors in their upper level products, as shown here.

Furutech replied already:

The listed products (FI-46, FI-48, FI-50) have pure OFC grade copper with no nickel plating and direct gold or rhodium plating. It is not a copper alloy.
I hope this information helps.

Kind regards,
Graeme
Furutech Co., Ltd.
Tokyo

@rayleigh 

I have each one.of those plugs. Theory one I have not bought is the first 48 plated in silver. I have a few sets in rhodium and a few sets of the very best rhodium plug as well. Lol I cheaper out and bought four sets of the 48 rhodium ones and I have five sets of the Top one as well in rhodium  plating. I also bought one set of the 15 in copper. I have a neotech gold as well have not tried that on anything yet. The basic copper plug set to me has the resolution  of the rhodium  plated ones and the musicality  of the gold plated one but not the detail of either of the other two. I bought some of the carbon fiber covers I slipped over the plug and iec ends. That did make them a bit better. Where I liked those covers the best was over the 46 gold plated plugs the resolution  got better and still had the swing of the gold plated ends. Also I have some of the best rhodium  receptacle s and some of the best gold receptacles.  Some components  I like a rhodium  plug into a gold receptacle and vise Vera. Some sound best with all gold or all rhodium  in the chain. Lol that takes lots of time and listening  to decide  which way to go. 

Regards