Don't have the thread about your rudder shaft.
Did see this company (Palm Beach) that says
"Seaworthy will restore corroded shafts on both rudders and propeller
shafts which are pitted and causing the seals to leak. Many times,
corroded and pitted shafts can be fixed and give years of good service
after our restoration."
http://www.oceanalloys.com/seaworthy.html

Don't know what process they use, but might be worth calling.

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Vic