There's another way to solve your problem: rather than preventing it from mounting, you could have it automatically dismount after you log in to your user account.
This might not seems as neat as not mounting it at all (after all, the system has to mount then dismount it), but it does have some advantages:
1. It's very quick and simple to set up, and to disable at any time if you wish.
2., It means your disk is still available if you ever have to do some troubleshooting in the recovery HD or Safe Mode (say if your SSD is playing up or something).
Here's how to do it if you wish:
1. Open the Applescript editor (click on Spotlight in the menu bar and type 'applesc' and hit 'return' on your keyboard).
2. Copy and paste the following in the editor window:
tell application "Finder" to eject (first disk whose name starts with "Name")
3. Replace the word "Name" with the first word of the name of your disk as it appears in the Finder sidebar (not the first word in its pathname),. E.g., in Finder sidebar, my disk is called 'Buffalo 500GB HDD', so I'd put 'Buffalo' in the script).
IMPORTANT: be sure to retain the double quotation marks "" around the name of the disk.
4. Now let's test it. Click the 'Compile' button in the task bar and, assuming there's no errors, then 'Run'. Check in Finder sidebar that your disk has disappeared.
If you get any errors on compile or run try deleting the script and typing it by hand. Sometimes copying and pasting text over introduces buggy characters. If you type it, watch the punctuation. If you get errors and can't solve them, post back.
5. Assuming the test works, choose 'Save as' from the Applescript File menu and in the dialogue box change 'File Format' to Application. Choose a location to save to ( /Applications is preferred ) and click the 'Save' button.
6. Go to
> System Preferences... Users & Groups | Login Items.
Click the '+' sign in the Login Items tab, and add your new application to the list.
7. Restart the mac and test. The disk should dismount after the login process has finished.