Why Did My Titanium Anode Case Turn Purple when Plating Sulfamate Nickel?

I am using sulfamate nickel bath to electroform optical discs. All hardware that I use is titanium, and after a short ramp, I use 100A(~24V) with a cathode surface area of 0.25 ft2.

Recently, an anode case was dumped and cleaned, and to my surprise, it was completely PURPLE inside and out. Since there are 6 baths running on the same solution, I don't think that the problem lies there. It doesn't appear to be burnt. Does anyone have any suggestions for why it turned this color?

You have two something weirds. I have never seen titanium that would stand 24 volts anodic in a sulfamate nickel tank. It self destructs starting at about 9 volts or slightly lower. 400 amps per sq ft is an awesome amount of power that normally requires exceptionally turbulent flow to not tree like mad. Lacking any other information, I would have to guess that you somehow anodized the titanium, as deep blue or purple is the color formed in sulfuric acid at about 20 volts.

A. The problem that you have mentioned is puzzling indeed. I have seen purple shades on titanium in conditions when excessive current is passed through it causing it heat up or may be a loose connection that causes the heat buildup. But as Mr. James Watt has mentioned about titanium self destructing at 9 volts, I use it regularly at 18 volts for the last few years. The CD is around 100 amp/sq ft. I think it is the high CD that may have caused it. Nitin Kibe - Pune, India 2000 A. I have seen more than one anode basket destroyed by about 9 volts anodic. Being able to go to 18V anodic must have been done with a very low chloride level. If not that, I have no clue. James Watts - Navarre, Florida .