Rusty Keel

[Sootydog]

The boat has just been lifted and I have noticed a flake of rust about the size of my palm has fallen off.  The surrounding area looks flaky. The yard is suggesting sand blasting the keel back to bare metal, drying and cleaning with acetone followed immediately by an epoxy coat. I'm concerned that the sand blast will compromise the seal between the keel and the boat.  Other than a few unsightly rust spots everything else seems ok. Is this an overkill or required maintenance?

[sunshine]

If you want to do the job properly, then you do need to blast and epoxy it. Expensive boats have a lead/antimony keel which doesn't have this issue but bavarias along with all other boats at our end of the market have cast iron keels which will corrode once the paint/epoxy layer gets compromised. If left long enough it starts to look pretty scabby and the pitting can get quite deep. Some people are happy to wire brush and tidy up at antifoul time each year. In my case, the previous owner didn't get the coppercoat properly done at the bottom of the keel and it got pretty ratty (see pics).

I got my keel done last winter as part of re-coppercoating. The yard should be careful to blast in a way that doesn't damage the hull joint. I think they actually used salt to blast mine. Its also quite a precision job with a nozzle, not a huge hose spraying everywhere, so I wouldn't worry about the join assuming you use a reputable yard. You also want to get it done indoors in a dry atmosphere.

[Rampage]

It’s a fact of life with cast iron keel; they get rusty, some more so than others.  However, it’s all cosmetic, as despite the somewhat unsightly appearance of the putting, it’s s only a tiny fraction of the total mass of the keel.  So unless you’re thinking of applying Coppercoat or similar, then I think blast cleaning of the keel is overkill. 
I took my keel back to bare metal using an angle grinder a few years back, followed by any number of coats of primer and epoxy coating followed by antifoul.  A couple of years later, the rust was back, not as bad but bits appearing like chicken pox.
I now simply grind out the pox in the spring, apply epoxy primer and top coat and slap on the antifoul.  Rarely reappears in the same spot two years running....

[tckearney]

I had a similar problem with my B42 2000 version.  I just used a drill and wire disc to clean it, then four or five coats of Hammerite smooth followed by three or four coats of a two part epoxy and checked it last years after being afloat for two years and all was fine.   I did have quite a lot of rust.