BIP38 ("Passphrase-protected private key") utilises "Scrypt"... which is notoriously "slow" when it comes to attempting to bruteforce it. It was chosen for this very reason
![Tongue](https://bitcointalk.org/Smileys/default/tongue.gif)
As you can see from
the stats on this BIP38 bruteforce tool... it took 337.219 seconds to check 500 passwords! at a speed of roughly 1 passphrase per 0.675 seconds
This bruteforce tool was running at around 0.6s/passphrase during the run in
this video. ![Undecided](https://bitcointalk.org/Smileys/default/undecided.gif)
As the video presenter points out "it is not a very fast bruteforcer"...
There is also this one:
https://github.com/cculianu/brute38 (no idea on the speed)