Diffused Nickel Cadmium is turning orange at edges

I have having an issue with Ni-Cd, after diffusion bake the panels/parts are turning orange at the edges. Any ideas why?

The sacharin brightener in some nickel will turn yellow under heat, but I assume and hope you are using almost pure nickel, like from a sulfamate solution.

The "edges" would be high current density locations. Nickel does not "throw" as well as cadmium so the nickel would be richer on the edges after baking. When nickel oxidizes it first turns orange, then brown, and finally black.

To get a more balanced distribution of nickel, then get further away from the anodes and raise the pH about 0.2 pH.

An analysis of the orange powdery coating shows to be mostly cadmium, less than 0.1% Nickel