Does removing disk partition clean all the data?

Removing the disk partition will take away easy access to the drive, but it's not really destroyed.

The disk partition (in simple terms) organizes the data into a group, which can then be assigned a drive letter, Deleting the partition removes the 'group' assignment, but the data remains largely intact. 

The danger in just removing partitions is that any semi-tech-savvy individual could easily recover the entire contents of the drive, with very basic data recovery software.

If you want to avoid your time-consuming disk cleaning, you could wack the exposed circuit board with a hammer a couple times (the method I use). 

At least with that kind of damage, any would-be 'dumpster diver' would need substantial technical skills (and probably a class 100 cleanroom, or around $2000 cash for a professional recovery from a facility, such as Knoll-Ontrack or DriveSavers) to recover the data.

HOWEVER, if you are responsible for "data security" in your line of work, and your work is sensitive or interesting enough for outside entities to take an 'active interest' in the contents of your trashed drives, then you should probably be physically opening the drives, and smashing the platters..takes about 5 mins per drive. Data recovery from this type of destruction requires an electron microscope, which is exactly what it would take to recover data from a high-end software-based 'drive cleaning'/data shredder' app.