Corrosion behavior of polypyrrole (Ppy) coating modified by polyethylene glycol (PEG) doped ammonium bifluoride on AZ31 magnesium alloy

In this study, polypyrrole (Ppy) coatings embedded by polyethylene glycol (PEG) doped ammonium bifluoride (doped Ppy) was deposited on the AZ31 Mg alloy using cyclic voltammetry. Fluoride-nuclear magnetic resonance (F-NMR), thermal gravimetric analysis (TGA), and differential scanning calorimetry (DSC) results showed that the doping of fluoride in the polyethylene glycol molecule was implemented. Corrosion performance of the doped Ppy coatings was assessed by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques in 0.05 M NaCl solution. Field emission scanning electron microscopy (FESEM) and energy-dispersive x-ray spectroscopy (EDS) showed that doped Ppy coatings possessed higher corrosion resistance than that of Ppy coating. Charge transfer resistance of doped Ppy coating measured about 2 and 5 times higher than un-doped Ppy and Ppy coatings, respectively which were associated to the synergistic behavior of fluoride with polyethylene glycol as well as its release to the anodic zones.