Evaluation of corrosion protection performance of electroplated zinc and zinc-graphene oxide nanocomposite coatings in air saturated 3.5 wt. % NaCl solution

This work aimed to compare and evaluate the microstructure and corrosion behavior of electroplated pure Zn and Zn-graphene oxide nanocomposite coatings with considering the effects of brightener additives as surfactant, and various concentrations of graphene oxide as colloid in electroplating solution. Zn and Zn-GO nanocomposite coatings were electrodeposited galvanostatically over a mild carbon steel substrate. It was found that incorporation of GO into the Zn matrix and the presence of brightener additives lead to the production of a coating with finer morphology and glossy appearance compared to pure Zn coating. Also, it was revealed that adhesion strength of Zn-GO nanocomposite coating was two times higher than that of pure Zn coating. In order to comparing the corrosion behavior of the coatings, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), potentiometric and salt spray tests were carried out in air saturated 3.5 wt. % NaCl solution. Based on the results, Zn-GO nanocomposite coated mild steel has a higher corrosion resistance compared to pure Zn coated mild steel. In general, the corrosion resistance of the mild steel coated with Zn-GO nanocomposite was improved up to similar to 5-fold (from 105 to 510 Omega cm(2)), while its corrosion rate was reduced by up to 15-fold (from 32 to 2.4 mpy) compared to the mild steel coated with pure Zn. Fine-grained microstructure and high impermeability of GO to corrosive agents such as oxygen and chloride are responsible for greater corrosion resistance performance of the Zn-GO coatings when compared to pure Zn coating.