Corrosion Behavior of AZ91D Magnesium Alloy in Simulated Acid Rain

Corrosion behavior of AZ91D magnesium alloy in simulated acid rain with different pH values was studied by polarization curves and eletrochemical impedance spectroscopy(EIS),and the surface morphology after corrosion was observed by means of SEM.The results showed that the polarization resistance of the magnesium alloy became larger and corrosion current density decreased when the pH value of simulated acid rain rose.In solutions with pH value of 2.7 and 3.0,EIS consisted of two capacitive arcs,while with increasing pH value,EIS showed only one capacitive loop,an integrated film was formed on the alloy surface.The whole surface of AZ91D magnesium alloy was corroded in simulated acid rain,and corrosion extent decreased with increasing pH value.The white corrosion product mainly consisted of Mg,Al,S and O.