Here's an old letter I saved addressed to Lennard Zinn from Craig Calfee of Calfee CF Frames fame. There sure is a lot of conflicting info on the net from supposed experts on this subject so hard to know who to believe but Mr. Calfee is one I would listen to about grease and CF.
Dear Lennard,
Thankfully! An opportunity to dispel the myth that one shouldn't grease a carbon post! I don't know where the myth started, but carbon composites are not affected by grease. Our advice is simple: If the seatpost fits tight, grease it. If it slips, de-grease it. As has been known for many years, when aluminum and carbon fiber contact each other, galvanic corrosion can start. That is why Calfee uses a fiberglass sleeve as a seat tube shim. Aluminum seat tube (or sleeve) and a carbon post will result in corrosion of the frame and possible seizure of the post within the frame. A carbon sleeve on an aluminum post will result in corrosion of the post. Salty environments accelerate this corrosion. Anodizing merely slows it down. About the only common chemical that will hurt carbon fiber is paint remover (which attacks the resin between the fibers). But there are many solvents that will dull a nice paint job.
Craig Calfee