Cast iron is quite a good metal vs. corrosion, etc.
To enhance the corrosion resistance you can boil it in very hot water
for several hours or soak the surface with a phosphoric acid mixture to
change the surface bloom of ferric oxide to ferrous oxide ... this is
the SAME process for 'blueing' iron based alloys. Why cast iron is
such a good metal for water jacket applications is that the hot water
continually turns any ferric oxide to ferrous oxide. So 'blue' the
cast iron before you coat it with anything else.



In article ,
wrote:

On Tue, 22 Feb 2005 12:17:36 -0600, "Sail-n-Dive"
wrote:

I'm doing a bottom job on my boat that has a cast iron keel with a
centerboard slot. Most of the keel stayed rust free but the slot and the
bottom of the keel that often comes in contact with the bottom at low tide
are rusty. I'm going to chip and sand blast but I'm unsure of how to treat
the bare metal before applying the new bottom paint. Suggestions?
Quinton

Suggestion #1 - don't allow an iron keel to come in contact with the
bottom

Suggestion #2 - Several layers of epoxy covered by a hard bottom paint


Weebles Wobble
(but they don't fall down)