One Piece Episode 638

[Kraco]

Half the time Bartolomeo apparently just covered his skin with it since nobody noticed a thing. Are you saying even in that case haki wouldn't help? If it helped, then erecting a fully separate barrier would make no difference. If it didn't, then I'd say haki performs quite unpredictably. I tend to think it sort of nullifies all fruit powers on contact, thus allowing physical damage to act like it normally would. In this barrier's case, an attack using haki would simply pass through as if it was empty air.

[DarthEnderX]

I tend to think it sort of nullifies all fruit powers on contact, thus allowing physical damage to act like it normally would.

I don't think that's the case at all.

I think Armament Haki simply allows a person to strike a person's "spirit" as well as their physical body. So that if your physical body is immune to physical damage for some reason, you can still be hurt by it.

I haven't seen any evidence that it actually turns off fruit powers the way Sea Stone or the Dark Fruit does.