This doesn't necessarily imply Haki Imbuement turning a blade black temporarily. The idea being spoken of here is the permanent blackening of a blade. Constant imbuement with Armament Haki ...

He appears to be a powerful swordsman and he has been seen coating his blade in Armament Haki. Tamago is quite a skilled pirate, worth 429 million berries. He is extremely dangerous, largely ...

Everyone seems to have Conqueror's Haki now, reducing its rarity and original significance. There are problems with Observation and Armament Haki ... as a shockwave or black lightning around ...