Preparation of Sn-Ni alloy/Fluorographene Composite Coatings on Copper and Their Corrosion Behavior in NaCl Solution

Fluorographene (FG) is studied to produce Sn-Ni/FG composite coatings to improve the corrosion resistance to an aggressive environment. Before use, fluorographene is functionalized with amino/oxygen-containing groups, making functionated fluorographene (FFG) dispersible in an aqueous solution. Sn-Ni/FG composite coatings are electrodeposited on a copper substrate by dispersing FFG into the electrolyte bath. The effect of FG on the microstructure and corrosion behavior of Sn-Ni coatings was analyzed by scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy, X-ray diffraction (XRD), dynamic potential scanning, and electrochemical impedance spectroscopy (EIS). The amount of FG in the composite coatings was varied by changing the concentration of FG in the electrolyte bath. Sn-Ni/FG composite coatings with uniformly dispersed FG are successfully electrodeposited on copper substrates by dispersing functionalized fluorographene in a plating bath. Morphology examination of the coatings reveals that the addition of FG changes the grains from semispherical to interlock ridge. The crystallite size decreases and the compactivity of the composite increases with the increase in the FG content of the coatings when the content of FG in the bath is below 300 mg L -1 . Compared to the pure Sn-Ni alloy coating, the corrosion resistance rate increases with the amount of FG in the coatings. However, too much FG in the plating bath will lead to an increase in the corrosion rate because of its limited dispersion stability. The small grain size, compact layer, and hindrance of FG to ion diffusion are responsible for the good corrosion resistance of the Sn-Ni/FG composite coating to an aggressive environment.