I may have found a workaround for your problem: nickel plating.
It involves some nasty chemicals, so you might consider contracting this out.
Some info:
http://www.pfonline.com/articles/pfd0015.html
http://www.pfonline.com/articles/040102.html
http://www.proplate.com/nickel1.htm
http://www.proplate.com/nickel2.htm
http://www.caswellplating.com/kits/electroless.htm (also on eBay).
I'm looking into this right now, for a heat exchanger that I just picked up.