Preparation of conducting poly-pyrrole layer on zinc coated Mg alloy of AZ91D for corrosion protection

Conducting polypyrrole (PPy) film was successfully prepared on the zinc coated magnesium alloy of AZ91D by electrochemical oxidation under constant current control in sodium tartrate aqueous solution. The oxidation was started from the formation of zinc oxide and zinc tartrate, followed by PPy electropolymerization. Surface morphology and the layer structure were analyzed by using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The PPy coating exhibited protection properties of the zinc coated magnesium alloy against corrosion in sodium chloride aqueous solution. The PPy coating is assumed to enhance the open circuit potential of the zinc coated alloy and cause the alloy to be passivated.

► A conducting polypyrrole layer was electrochemically prepared on the magnesium alloy of AZ91D.
► The PPy coating consisted of the inner zinc oxide and tartrate and the outer PPy layer.
► The PPy coating maintained the passive state in 3.5% sodium chloride solution for 1–2 h.