Hello,
I often make a forced patina on my blades from 2442 or 01, helps to prevent rust and looks... cool
Important to clean the blade very good with soap, acetone etc.
I use hot water with added vinegar, the blade will start to bubble and within a 5 mins it will turn dark.
The 01 will not turn black, but grey (my 2442 will turn dark grey).
I whipe off some the patina and repeat, maybe use some steel wool. If you repeat this several times, it will come out an even dark grey patina.

Regards
Nicolas