Can't unlock encrypted external drive with filevault (osx) I formated my external drive on mavericks, and then on Lion, sometimes I had to wait some time to unlock the volume. Other times I had to do a disk repair and only after that OSx accepts my password to unlock the volume.

This issue is described here: http://forums.macrumors.com/threads/cant-unlock-encrypted-external-drive.1668423/page-2

Now I can't unlock, regardless of the waiting or the number of times i do a disk repair. I even made an upgrade to El Capitain, but without sucess. Tried in another OSx computers, but without success.

Maybe there is a chance of some corrupted data, due to not eject the disk properly some times. 
I'm pretty sure of the password, so, what i can do to unlock/decrypt my data from this volume? Can I create a volume image with dd, or another tool and then try to decrypt? There is any tool available to do this?
Sadly you are going to have to get that volume unlocked before you can copy any data from it.  The encryption cannot be "cracked" in any reasonable period of time.

If there is corruption, the volume/data may be irretrievable.

Can you find a machine running Lion and try to unlock it one last time there?  If that works, copy all the data off the volume and onto a new volume.