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It has been illustrated by researchers that graphene and graphene oxide can be embedded into metal matrix to produce highly corrosion resistant composite coatings. This paper investigates the effect of graphene oxide (GO) on microstructure and corrosion behavior of Sn-rich, SnNi-GO composite coatings. SnNi-GO composite coatings were electrodeposited on mild steel substrate by dispersing chemically synthesized GO into the electrolyte bath. Amount of GO in the composite coatings was varied by changing the concentration of GO in the electrolyte bath used for the electrodeposition. Morphological characterization of the coatings revealed the presence of rod shaped features in a flat matrix. Volume fraction of the rod-shaped features progressively increased with the addition of GO into the coatings. Structural characterization revealed the presence of Sn rich phase along with Ni 3 Sn 4 , Ni 3 Sn 2 and Ni 3 Sn intermetallic phases in all the coatings. Crystallite size of the Sn-rich phase decreased significantly due to the addition of GO into the coatings. Corrosion behavior of the coatings was examined through potentiodynamic polarization and electrochemical impedance spectroscopy methods. A significant improvement in the corrosion resistance in terms of reduction in corrosion current and corrosion rate and increase in polarization resistance was noted in the case of SnNi coating containing GO. Corrosion resistance of the coatings increased with increase in the GO content. Microstructural characterization of the cross-section coating sample performed using transmission electron microscopy (TEM) technique revealed differences between the microstructures of coating containing different amounts of GO. All the coatings with GO contained almost pure Sn grains with Ni present at the grain boundaries. Size of the Sn sub-grains within the larger Sn grains, however, decreased with increase in the GO content in the coatings. Smaller Sn sub-grains and presence of Ni at the grains boundaries led to quicker formation of the corrosion products that are SnO and NiO with increasing GO content in the coatings eventually yielding the highest corrosion resistance value for the coating containing maximum amount of GO. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of graphene oxide (GO) on morphology, microstructure and corrosion behaviour of Cu-GO composite coatings. Cu-GO composite coatings were electrodeposited on mild steel substrate by dispersing chemically synthesised GO into a Cu electrolytic bath. Anionic surfactant (sodium lauryl sulphate) was used to obtain uniform and compact coating morphology. Incorporation of GO into Cu matrix produced a finer granular coating morphology with a strong 〈220〉 preferred orientation. The analysis of electrochemcial corrosion test results revealed that steels coated with Cu-GO were invariably more corrosion resistant compared to both bare steel and pure Cu coated steel. Extent of the reduction in the corrosion rate increased with increasing amount of GO in electrodeposited Cu matrix. Improved corrosion resistance of Cu-GO coatings was related to 〈220〉 texture and high impermeability of GO to Cu + ions and dissolved O 2 in the chloride media. [ABSTRACT FROM AUTHOR]

Electrochemical properties of pure SnZn and SnZn-graphene oxide composite coatings were determined and compared. Graphene oxide (GO) was synthesized by the modified Hummer's method. SnZn-GO composite coatings were electrodeposited over a mild steel substrate. Amount of GO in the composite coatings was varied by changing the concentration of the GO dispersed in the electrolyte bath used for the electrodeposition. Morphological and topographical characterization revealed that the relative smoothness and the compactness of the coatings increased with increase in the concentration of the graphene oxide in the coatings. Texture and the crystallite size, however, did not show any significant variation with the concentration of GO in the coatings. Corrosion behaviour of the coatings was examined through potentiodynamic polarization and electrochemical impedance spectroscopy methods. A significant improvement in the corrosion resistance in terms of reduction in corrosion current and corrosion rate and increase in polarization resistance was noted in the case of SnZn coating containing GO. Corrosion resistance of the coatings increased with increase in the GO content. Microstructural investigation conducted using transmission electron microscopy revealed that the pure SnZn coating contained large scale segregation of Zn-rich and Sn-rich phases. Whereas, the presence of graphene oxide facilitated relatively uniform distribution of Zn phase in the Sn-rich matrix. Uniform distribution of Zn-rich phase causes uniform formation of the corrosion product that is ZnO over the coating surface in case of SnZn-GO composite coating. This is responsible for greater corrosion resistance performance of the SnZn-GO coatings when compared to pure SnZn coating. [ABSTRACT FROM AUTHOR]