Electrochemical behavior of Mg-Al-Pb alloy in 3.5% NaCl solution

Abstract

An investigation on electrochemical behavior of Mg-5%Pb alloy, Mg-6%Al alloy and Mg-6%Al-5%Pb alloy (mass fraction) in 3.5% NaCl (mass fraction) solution was conducted using electrochemical measurements and corroded morphology observation, in which solid solution and the as-aged state of each alloy were compared to discuss the influence mechanism of lead and aluminium on the electrochemical properties of alloys. The X-ray diffraction (XRD) analysis was performed to make microstructure characterization. The electrochemical results indicate that the corrosion of Mg-5%Pb alloy is predominated by homogeneous pitting and dissolution of PbCl2 film due to Cl ions attack, while corrosion crevice propagates along grain boundaries in solid solution of Mg-6%Al alloy and the micro galvanic corrosion also plays vital role in Mg₁₇Al₁₂ phase containing experimental alloys. The co-existence of lead and aluminium in magnesium alloy increases corrosion current density and electrochemical activity as well. The comparison between solid solution and the as-aged state demonstrates that Mg₂Pb and Mg₁₇Al₁₂ somewhat increase corrosion resistance but lighten anodic polarization by facilitating corrosion product flaking off.

Keywords

Mg-Al-Pb alloy / electrochemical behavior / corrosion / solid solution / as-aged state

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