Effect of TiO2 Pretreatment on the Corrosion Properties of Inconel 625 Overlay-Welded Low-Alloy Steel

Abstract Overlay welding with corrosion-resistant alloys is widely used to enhance the durability of components operating in corrosive environments such as offshore, petrochemical, and oil & gas. This study investigates the influence of oxide-based surface pretreatments of titanium dioxide (TiO2) on the corrosion performance of Inconel 625 overlays applied to low-alloy carbon steel using the Gas Tungsten Arc Welding (GTAW) process. Two sets of samples were prepared one with TiO2 surface activation as a pretreatment and other one without any pretreatment or surface activation. Corrosion resistance was evaluated through potentiodynamic polarization and coating capacitance is determined by electrochemical impedance spectroscopy (EIS) in a 3.5% NaCl solution. Microstructural examination using optical microscope was performed to analyze grain structure and surface morphology of weld overlay, interface between overlay and base material and base material. TiO2 demonstrated superior corrosion resistance compared to without flux sample, likely due to the formation of a more stable and adherent passive oxide film on the weld surface. The findings of this study that oxide-based surface activation using TiO2 as a pretreatment can significantly enhance both electrochemical and atmospheric corrosion resistance, making it a viable pretreatment strategy for extending the service life of Inconel 625 overlayed components in aggressive environments.