If the shaft cannot rotate, you can repair the shaft by the way of repairing the hydraulic cylinder. brush with the fast copper and fast nickel solutions.
If the shaft can be turned on a lathe, the best way is to plate self-replenish nickel due to this kind nickel is easy to use and have a good hardness. But you can also brush copper first and the plate self-replenish. One morething ,to brush self-replenish nickel you must use nickel as anode.