Metal oxides and novel metallates coated stable engineered steel for corrosion resistance applications

Highlights: • Various tungsten based metallates and mixed oxides have been coated on steel surface. • The proposed stoichiometry Fe_0.375X_0.4375O_0.1875 and WX_0.33O_2.66 exhibit high stabilities. • The corrosion resistance was found to be highest in the case of boron mixed tungstate oxide. Functional materials in the family of ternary metal oxides and metallates have seen surging interest in recent times due to their diverse applications. In this study, we report first-principle calculations and experimental characterization results for a variety of newly mixed metal tungstates and other oxides, which have the potential for corrosion protection of steel in extreme environments. These new mixed oxides/tungstate family have the chemical stoichiometry Fe_0.375X_0.4375O_0.1875, WX_0.33O_2.66 and FeWX_0.5O_3.5 (Where X$\equiv \mathrm{Ni},\mathrm{Mo},B$), exhibit high electrostatic binding forces resulting in high stabilities as revealed from DFT calculations. Different parameters like entropy, enthalpy, electrostatic forces, and solid solution formability were calculated from first principle calculations for the different stoichiometries, based on which the most stable structure and composition was predicted. By appropriate tuning of chemical composition, such novel mixed metal oxides and metallates were synthesized through a unique solution-based route and further coated on steels. After phase and morphological examination of these coatings, they were subjected to harsh extreme environments, and their corrosion resistive behavior was studied through polarization tests and electrochemical impedance spectroscopy (EIS). The corrosion resistance of many of these coated substrates was observed to be robust with high coating capacitance, and corrosion resistance was found to be highest in the case of boron mixed tungstate oxide, which is also consistent with first principle calculations that reveal high stability. Incorporation of these stable ternary mixed metal oxides/metallates (tungstates) can have great potential for preservation and the protection of steel in harsh environments.