If impressed current cathodic protection is used, or a simple circuit through the hull with sacrificial anode, then the iron rust would be minimized, in fact it’s actually the same process which gives rise to biorock, so the micro-cracks would be filled in, and the hull would grow.
At 22 watts per gram, it can easily do maintenance repairs,
such as filling in micro-cracking, with as much electricity as a lightbulb.
It would be interesting to grow the seasteads in spiral shapes like seashells,
the accretion is focused at the cathode, so can have it close to the new construction area.