I was at my in-laws house earlier today looking at a Zalman CNPS7700Cu (the best pre-heatpipe-era cooler invented) that was in a computer I had pieced together for them a long time ago when I realized that although it was made of solid copper with (as far as I was aware) no special treatment, it wasn't showing any signs of oxidization (discoloring/turning green). To me this seemed strange, as I don't think copper products are given anodized platings and it's definitely not painted, so... why isn't it noticeably oxidized? It's likely over 3 years old and has been in contact with a computer that's on probably 18 hours/day.

I tried researching an answer, but all I can get is that as far as any old review sites knew at the time, it was solid copper and none make any mention of a coating. Metallurgical sites etc all seem to be of the consensus that anodizing isn't something you see on solid copper and suggest a paint/varnish or just cleaning copper every so often... so, I guess I'm hitting a dead end.

Any thoughts?