 The use of such coatings would require addition coatings that are more oxidation resistant, such as alumina or mullite.The bond-coat is an oxidation-resistant metallic layer which is deposited directly on top of the metal substrate.It is typically 75-150 μm thick and made of a NiCrAlY or NiCoCrAlY alloy, though other bond coats made of Ni and Pt aluminides also exist.