Electrochemical and Mechanical Investigation of Newly Synthesized NiO-ZrO2 Nanoparticle–Grafted Polyurethane Nanocomposite Coating on Mild Steel in Chloride Media

Abstract

NiO-ZrO2 nanoparticles were prepared and characterized by Fourier transformed infrared spectroscopy (FTIR) and x-ray diffractometer (XRD) analysis. The NiO-ZrO2 nanoparticles were incorporated into polyurethane (PU) and the resultant polyurethane (PU)/NiO-ZrO2 nanocomposite was coated on the steel sample. The anticorrosion behavior of the PU/NiO-ZrO2 nanocomposite coating was electrochemically studied and compared with pure polyurethane coating by scanning electrochemical microscopy (SECM), potentiodynamic polarization studies and electrochemical impedance spectroscopy (EIS). EIS studies showed a pronounced protection performance for PU/NiO-ZrO2 coating in natural seawater. SECM analysis measured lower current for the PU/NiO-ZrO2 at the scratch of the coated surface compared to PU coating. The surface characterization and elemental composition of the coated samples were examined by surface morphological studies (SEM/EDX). Dynamic mechanical analysis (DMA) test was also carried out to examine the coated nanocomposite. The results provided valuable information about the protective performance and failure analysis of PU/NIO-ZrO2 nanocomposite coated surface. Field emission-scanning electron microscopy/energy-dispersive x-ray (FE-SEM/EDX) analysis was used to examine the corrosion products formed on the surface of coated sample. The formation of thin films of oxides and chlorides of Ni and Zr blocks the penetration of corrosive ion in the coating/metal interface. It was revealed from the mechanical properties of the nanocomposite and pure PU coatings that mixed metal oxide nanoparticles (NiO-ZrO2) enhanced mechanical as well as protection properties of the polyurethane coating against corrosion. A possible protection mechanism is also proposed.