its invisible unless you use hardening
you see how he doesnt use black coating but still hits a logia in logia form and causes damage
these are 4 pages in a row in the same chapter so i dont really know how ppl say oda forgot or its an artistic choice or w/e. we just dont see people using hardening until after the timeskip.

you see how he doesnt use black coating but still hits a logia in logia form and causes damage

these are 4 pages in a row in the same chapter so i dont really know how ppl say oda forgot or its an artistic choice or w/e. we just dont see people using hardening until after the timeskip.
No one in manga after pointed out about haki being visible. No one ever said "look his weapon/arms became black so he is using haki". That shit never existed.