I did something like you are proposing, but I used copper electrical wire. I had to strip the insulation first, but it worked well. I forget the gauge of the wire, but I think that it may have been 12 gauge or 14 gauge. Anyway, it works fine for me. I don't think that you should have any problem if the wire is heavy enough. Also, I think that you are on the right track with using copper wire (I am assuming that you have a copper immersion chiller). With that there should be no problems.
Mark