This shows the line between wet and dry on my 10" saw after sitting 4 or 5 weeks. About a month ago I cleaned out the saw after using water with a small amount of borax, with poor results on corrosion.  I had just stirred in some borax into cold water. This time, I boiled a liter of water, stirred in about 3/4 cup of borax until dissolved, and that seems to inhibit rust nicely. I think my first attempt just resulted in borax settling to bottom of tank.

Thanks for the nice borax solution tip.  Glad to see that it's working now.