After screws are cleaned by most methods it leaves the steel very
prone to further rusting.  I once left on the floor a very large box
of screws which the cat mistook the box for a litter box.

Well, it did require some thorough washing; you don't need details.
Some were rusted by the time I noticed the cat's indiscretion.
I cleaned them with white vinegar and salt, then boiled the screws
and added a small amount of cooking oil which left a light film on
the screws.

Is there a better way of preventing rust?  Bluing may have been used
on some old screws but does it prevent rust?

Bill Chapman
La Quinta, California
(pronounced locally as La Keenta, which means a country house)