Can Sanji use COA(Color of Arms/Busoshoku)? He didn't use it on Punk Hazard and he wasn't on Dressrosa. However it was mentioned in the manga when he battled his father in the current whole cake island arc that his haki is strong but it was not specified which haki. 

Can Sanji use armament?
Yes, Sanji can use CoA, even if it was not shown yet to my knowledge. We know this from Chapter 668, when Law asks Luffy who of his crew is able to fight Caesar, a Logia user.