Assessment of the microstructural features and electrochemical corrosion behaviour of nanostructured Gd2Zr2O7 EB-PVD TBCs under three salt conditions

Abstract

Improving corrosion resistance is a challenging task, as it determines the life time of thermal barrier coatings (TBCs). In this regard, this study was aimed to characterize the electrochemical corrosion behaviour of nanostructured Gadolinium Zirconate in three different corrosive salt conditions such as Na2SO4 + 55 wt% V2O5 (SM1), Na2SO4 + 10 wt% NaCl (SM2), and Na2SO4 + 7.5 wt% NaCl +7.5 wt% V2O5 (SM3). The uniformity of the coated surface was verified by mapping the vibrational bands associated with Gd and Zr using FT-IR and Raman spectroscopy. The coated surface possessed a uniform columnar structure with leafy appearance. Potentiodynamic polarisation studies and electrochemical impedance spectroscopic data demonstrated that the nanostructured GZ exhibited superior corrosion resistance properties under SM1 salt condition as compared to SM2 and SM3 conditions. SEM and EDS analysis were used to evaluate the nanostructured GZ coatings that were subjected to electrochemical corrosion. In the case of SM2 and SM3 conditions, the surfaces were degraded with microcracks. The formation of corrosion products and the exposure of succeeding layers as a result of corrosion were also characterized using FT-IR, Raman spectroscopy, XRD technique and 3D optical microscope.