Oh.....one other note I forgot...If you have zinc and nickel together the zinc will destroy itself lonnnnng before it causes any problem with the nickel.
Sound like you understand the corrosion process so you know Zinc is a sacrificial metal and nickel is way up on the nobel list from zinc.
Hope this helps you get a better footing on the problem.
Let me know if I can assist any more.
48BUICK