Better would be to put the sculpture on a post with sealed roller bearings
top and bottom than use a lazy susan type bearing. The dirt will stop the
lazy susan bearing before the rust will if you use one.
If you really want to use a lazy susan bearing, probably the best will be to
integrate it into the sculpture if you can with large stone or glass balls
and a ground in track to support the item. A very shallow groove on the
ground side will tend to keep the dirt from being really bad with the
bearing

--
Bob May
Losing weight is easy! If you ever want to lose weight, eat and drink less.
Works every time it is tried!