"Here's a few other things
"Here's a few other things to consider regarding corrosion. The rate of corrosion of any material is temperature dependant. The hotter the material, the faster it corrodes. If it's cold enough for water to freeze, the rate of corrossion of iron is dramatically less than when the engine is at operating temperature. That doesn't mean it isn't happening, but it is significantly reduced.
Another term for corrosion is oxidation. In order for iron to turn into iron oxide (rust) is needs oxygen. If the susceptable material is not in contact with O2, there will be no corrosion. So putting the engine in an antifreeze bath will certainly eliminate or nearly eliminate corrosion... while it's in lay-up... i.e., while it's cold, and the rate of corrosion is almost insignificant anyway.
I it was think Rod that also mentioned in another thread that when bare iron first starts to undergo general corrosion, a very hard and nearly impermiable oxide layer forms on the surface and sheilds the underlaying material from oxidation. The key to success in preservation here is promoting general corrosion and not pitting corrosion. Material submersed in an ionic solution (i.e., salt water) will tend to exibit pitting corrosion over general, especially when it's hot. Lake, river and tap water aren't completely free of minerals and ions. Granted, it's a lot less concentrated, but they are still there. Warm, dry air, on the otherhand is virtually free of ions, but plentyful in oxygen... a perfect environment to promote general vs. pitting corrosion. The only problem is you never get all the water out of an engine block and all the little pockets where there is water and air are going to corrode relatively faster (but once cold, "relatively faster" is still going to be very slight), unless you can come up with some kind of air-dry system and leave it running until all the moisture is removed. Aside from Big Navy, I don't think anybody does this.
Conslusion...
You're not completly pissing in the wind by filling your block with anti-freeze. But in the big sceme of things, it's probably not making that big of a difference WRT corrosion or protecting from freezing as compared to leaving it dry. Regions that don't go below freezing and stay there for the whole winter are the exception, and would probably see some benefit from anit-freeze lay-up."