Powers & Abilities Black blades are application of CoC Barrier.

[Cruxroux]

Thanks to @HellBlazer04 i just noticed this.

Roger confirmed, Xebec was Using CoC barrier to cancel out their Conqueror attacks. And he was scratchless the entire time.

Guess what mihawk said

Mihawk was fighting Shanks one of thr strongest Conqueror Haki user.

You can already see, xebec sword turning black slowly,
And black blades are made over time over numerous battles.

Just like Ryou was used by Luffy and Zoro. In different ways.

CoC barrier is used differently by Xebec and Mihawk.

And mihawk is Scar less the entire show. Whereas shanks admitted getting Scars from Mihawk.

 

[HA001]

So you fight with a coc barrier which is flame like which forges a kokuto
With the concept being when goku and gohan kept super saiyin in base looking in the cell saga
So when you use your haki with your kokuto it is even stronger.

 

[Sentry22]

The scars are from an encounter with BB not Mihawk.