Electro chemical characterization of V$_X$Nb$_Y$C$_Z$/Bi$_X$Ti$_Y$O$_Z$ coatings produced through thermo-reactive diffusion and the sputtering technique

Abstract

We present an experimental study of the structural evolution of a bilayer V$_X$Nb$_Y$C$_Z$/Bi$_X$Ti$_Y$O$_Z$ coating produced via thermo-reactive diffusion (TRD) and the RF sputtering process on D2 steel substrate. The TRD treatments were carried out in a molten mixture consisting of borax, ferro-niobium, ferro-vanadium, and aluminum, at 1313 K for 3 hours, using a resistance-heating furnace. Bi$_X$Ti$_Y$O$_Z$ coatings were deposited using RF magnetron sputtering on TRD coatings, in order to carry out a study of the corrosion behavior of this compound. The crystallographic structure of the coatings was determined via X-ray diffraction (XRD), the corrosion resistance was analyzed through the potentiodynamic polarization test (Tafel Extrapolation) and electrochemical impedance spectroscopic analysis (EIS). XRD patterns showed that the ternary coating (VNbC$_2$) was preferentially oriented along the [200] direction with a cubic-centered face structure, and the Bi$_X$Ti$_Y$O$_Z$ coatings were amorphous. The electrochemical studies showed that the resistance corrosion of the coatings increased with respect to the bare substrate, and that polarization resistance in the bilayer coatings increased with respect to the ternary coatings, suggesting that the titanate has anticorrosive barrier effects.