Hot corrosion of a novel (Ni,Co)O/(Ni,Co)Fe2O4 composite coating thermally converted from an electrodeposited Ni–Co–Fe2O3 composite coating

Ni–Co–Fe2O3 composite coatings were successfully developed by sediment co-deposition. In order to improve their hot corrosion resistance, a pre-oxidation treatment was conducted at 1000 °C for 6 h. The corrosion behaviour of the oxidised composite coating was investigated at 960 °C in an atmosphere consisting of a mixture of Na3AlF6–AlF3–CaF molten salts and air. They exhibited good hot corrosion resistance due to not only the pre-formed oxide scale with (Ni,Co)O and (Ni,Co)Fe2O4 phases after pre-oxidation, but also the formation of (Ni,Co,Fe)Al2O4 phases in the outer layer and a well-distributed NiFe2O4-enriched phase along the grain boundaries in the subscale area during the corrosion process.

► Ni–Co–Fe2O3 coatings are successfully developed by sediment co-deposition method.
► The oxidized coated specimens produce a protective oxide scale with good adhesion.
► The newly formed (Ni,Co,Fe)Al2O4 in corrosion process was protective.
► Intergranular precipitates can restrain the further attack of the molten salt.