I've tried this:
Having the UUID for the volume (seen on disk utilities) to hide during the mount process, from an admin account edit the /etc/fstab file:
sudo pico /etc/fstab/
Add a line with the UUID for your volume and the mounting point information, for example:
UUID=EXAMPLE-5558-3BB3-9FA9-EXAaaaaAMPLE none hfs rw,noauto
Save the file.
But it does not work. Any ideas?