Corrosion behavior of Mg-Al-Pb and Mg-Al-Pb-Zn-Mn alloys in 3.5% NaCl solution

Mg-6%Al-5%Pb and Mg-6%Al-5%Pb-0.55%Zn-0.22%Mn (mass fraction) alloys were prepared by induction melting with the protection of argon. The corrosion behaviors of these alloys were studied by electrochemical measurements and immersion tests. The results show that at the corrosion onset of Mg-Al-Pb anode there is an incubation period that can be shortened with 0.55%Zn and 0.22%Mn additions in the magnesium matrix. The corrosion rate of Mg-Al-Pb anode is mainly determined by the incubation period. Short incubation period always leads to high corrosion rate while long incubation period leads to low corrosion rate. The corrosion rates based on the corrosion current density by the electrochemical measurements do not agree with the measurements evaluated from the evolved hydrogen volume.