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Zev, if you want to speak to keel experts call up Mars Metal, who are the foundry making a large number of the new and replacement (special purpose) keels in the US. They are good folks and even if you aren't going to buy a new keel (and you shouldn't need one) they can give you information about maintenance and inspection.
4130 Morris Drive;
Burlington, Ontario, Canada L7L 5L6
Phone 905-637-3862; fax 905-637-8841
I don't know what your keel is made of but as noted you can test it with a magnet, or check online with owner's groups to find a spec for it. Keel bolts usually are made of stainless steel "J" shaped rods, which are hung in place over the keel as it is cast from molten metal, so they form solidly into it as it cools and hardens. Removing them is possible, but difficult. You would cut into the keel from the side, making a hole where the bottom of the "J" is, to cut that out. Then drill down from the top to remove the stainless bolt, and that's a huge task. So the practical solution to bad keel bolts is to sister them in between the existing bolts, tying into the cross-members or adding new ones if needed. That's extreme, and probably NOT your problem.
Most keel bolts are stainless, but the washers and bolts on the top of them are usually carbon steel--and if only the washers are not stainless, that's all it takes to cover the tops of them with rust. Usually that's all the problem is.
You can clean them up as best you can with a wire wheel or rust removers (Naval jelly, acid, etc.) and see if it is just surface rust. If not, you would want to remove one of the nuts to see if the corrosion is just the nut--or the bolt as well. You can usually do this with a large wrench and a pipe to extend the handle. (There are torque settings for these bolts, typically in the 100-300 foot pound range IIRC. ) If the nut is really frozen, you can saw most of the way through but stop short of the bolt, then crack it off with a chisel or automotive nut cracker. (Yes, there is such a tool.)
Odds are you just need to clean it up, and then apply something to prevent further rust, and keep the bilge drier. Some people try to "pot" the top of the bolts with epoxy or another permanent sealant. Others use wax or tar (tar makes a mess but works) or grease, which allows you to remove it and replace it from time to time so you can inspect the bare metal easily.
This is all assuming you have an external keel. If you do, there's also a less traditional way to reinforce it. You loosen all the keel bolts and rebed the keel (clean out the keel/hull mating surfaces, CLEAN, and then apply new bedding compound & retighten) using 3M 5200 permanent adhesive. If you do that, the adhesive is so strong that when properly applied, it can hold the keel even if all the bolts are stolen by burglars in the middle of the night.
But get down to bare metal to inspect the bolts, call Mars after that, and then see what's happening. You're right to be concerned about basic issues like the keel, and even if it is only cosmetic rust, to clean it off.