There is no such thing as "centrifugal force." It's a "pseudoforce" which simplifies some problems but clouds the reality of the situation. In your setup, the coin starts out with zero momentum. Since the disc is frictionless, there is nothing (no force) acting on the coin -- where of course I'm ignoring the vertical force due to gravity and the equal-and-opposing vertical force applied by the disk to keep the coin at a fixed altitude.
Now, it might be interesting if you started out with a spinning disk that was not frictionless and had a coin sitting on its surface, then at some point scientificomagically turned off the friction. Calculate the coin's momentum at that instant and see what happens.