Microstructure and corrosion properties of nico-graphene oxide composite coatings

NiCo (10% Co) and NiCo-GO composite coatings were electrodeposited over mild steel substrate. The amount of GO in composite coating was varied by varying the concentration of GO dispersed in the electrolytic bath. Six different NiCo-GO composites coatings were produced. Scanning electron microscopy, X-ray diffraction, Energy dispersive X-ray analysis were used to investigate the effects of adding graphene oxide particles on the surface morphology and grain size of the composite coatings. Electrochemical impedance spectroscopy and Potentiodynamic polarization were performed in 3.5% NaCI solution to observe the electrochemical behaviour of the composite coatings. All the coatings exhibited uniform and crack free morphology. Graphene oxide nanoparticles acts as additional nucleation sites during electrodeposition hence a reduction in grain size is observed. GO addition in the coatings lead to an enhanced corrosion resistance up to an optimum GO concentration after which it deteriorates. EBSD data revealed that the sample exhibiting maximum corrosion resistance also has high fraction of low angle grain boundaries 0<5°. (author)