Recycled Copper...safe to use?

[Copper Head]

Hi all. Great site, tons of good information. Looking for a couple of opinions if anyone is willing to give some feedback. I recently picked up 1 foot of three inch copper from a metal yard that recycles metal. I want to use this to cut plates for a bokakob I am in the process of making. On the inside of the pipe there is green (corrosion) discoloration. My concern is I have no idea what been going trough it, could be toxic, maybe not. Either way, if I clean it in a good acidic bath (moradic acid) would that get rids of any possible surface contaiminats if they are even there? I don't think copper is porrous so, after a good cleaning would it be good to go?

Alternatively, can you use stainless for the plates vice copper?

Thanks.