Looking for a coating for a high temperature auger (auger is hollow
and hot oil circulates thru it at 500 degrees F). Auger dimension is 6
foot O.D. by 16 feet long made of 1018 mild steel. Rpm is 10 max.
Auger runs clockwise 9 to 10 minutes then reverses. Hopefully a
coating will keep biosolids from sticking as they dry. Considering
teflon, ceramic, etc. Help!

Just as a non-detailed suggestion, you could consider thermal spraying.
Thermal sprayed coatings are generally very durable and can be
engineered to suit practically any purpose including strengthening,
insulating, protecting, etc?
Non-Stick thermal spray coatings are a relatively recent addition to
the usage of this technology, but you can find companies who will do
it.
However, you will have to look for quotes to see whether it would fit
in your price range.

Here is a site you can look at to start.
http://www.engineeringtalk.com/news/poe/poe118.html

Another,  more feasable suggestion.
http://www.magnaplate.com/
The company I am working for is currently using this to prevent
urethane from adhering to molds that we use.  It works great.  The
company has a wide range of coatings and coating processes, and they
will work with you to help determine what you need.  After talking to
them about what we were doing and what we needed, the company sent us
several samples to test out to see which one worked the best.
if you are still looking for a coating for your auger, you should
contact magnaplate.  Their representatives will be able to give you
much more detail in what they can do for you.
I hope this helped.