My previous boat had an iron keel (Paceship PY23) so this topic still catches my attention.
Check out this article from Practical Sailor magazine . . .
Practical Sailor - Keels: Minor Maintenance and Repair - Tips Article
Good Old Boat magazine also had an excellent article on this several years ago but I can't seem to find it at present.
Paceship Chance 32/28 "Westwind"