Plasma-sprayed coatings of yttria-stabilized ZrO 2 and Al 2 O 3 .TiO 2 used as a protective barrier on β-Si 3 N 4 -based sialon ceramics were investigated. The coatings showed better cohesion with the pre-oxidized surfaces due to the reaction between the SiO 2 -rich oxidation layer and the coating materials. Formation of low thermal expansion zircon and aluminium titanate on the pre-oxidized ceramic was studied using scanning electron microscopy and X-ray diffraction. Preliminary experiments on oxidation and molten metal immersion, showed that the coatings provide significant protection against oxidation and molten metal attack.