<< If the plain iron carriage bolt was still functioning after 32 years, the
new stainless
bolt, upgraded in size from 3/8 to 7/16, could conceivably outlast the
skipper. >>
Unfortunately, Stainless does not like to be hidden and must be open to air or
it will rust where not aired. That is reason for yellowish streaks that form
below boarding ladder bolts after a while. Pig Iron (not steel) seems to rust
on the surface (like aluminum), the surface rust keeps the underlying metal
from continuing to rust. That is why Cruise ship mooring bits are made of pig
iron. That is also why antique wrecks with iron nails still have the nails
after 100's of years under salt water...
My ole Columbia 22's keel was pig iron and was not fiberglassed over. Usually
lasted 3 years before getting sanded for bottom paint.
My understanding is that monel is much softer than pig iron, steel or
stainless. So it would wear from friction a lot quicker.
Best
SF