Would it be at all useful to add a piece of solder wick (braided copper wire used to remove solder - available at Radio Shack) to the chassis, connected to the metal robot frame via a 1 MegaOhm or so resistor, just to limit inrush current? That or connect a Varistor, Transorb (zener), gas tube or similar device? Afrer all, it's not the voltage, it's the current that causes the real damage.
Ask the guys that routinely service the high-voltage transmission lines from a helicopter. (Check out
http://www.haverfield.com/) I don't know if they grab the 765,000 volt lines or not, but they do get ahold of some pretty high voltage lines, like in excess of 250 KV ( and I understand it smarts a bit).
Grounding and surge suppression is an art in and of itself.