Doeas an encryption wipe all hidden data?

[Der_Affenkoenig]

Hello, i discovered a couple days ago VeraCrypt, and it looks that this Tool is very awesome.

But i have a question:

I use a external HDD as Backup for sensitive data.
If I encrypt the entire HDD with VeraCrypt, then will all existing data blocks be overwritten,.... also my invisible data blocks from already "deleted" files?
Or should I completely delete the partition, overwrite the "hidden" Data with "cipher /w" or "WipeDisk" before i encrypt the HDD with VeraCrypt ?

The Stored Data, which are on the HDD are not that important (they are important, but not at the moment), its just an backup from files of my Computers, so if they get lost, when i encrypt the HDD, its not that bad.
I will copy them again, after the HDD is encrypted.

[Enigma2Illusion]

Yes. VeraCrypt will encrypt the entire partition including unused space as long as you do not select quick format.

VeraCrypt cannot encrypt sectors that have been marked bad.

https://www.veracrypt.fr/en/Reallocated%20Sectors.html

When encrypting in-place, meaning keeping existing data, once VeraCrypt finishes encrypting the partition, you will need to remove the Windows assigned drive letter using Windows Disk Management. Then mount and assign a drive letter via VeraCrypt.