Corrosion behavior of AZ91D magnesium alloy in sodium sulfate solution

The corrosion behavior of as‐cast AZ91D magnesium alloy in 0.1M sodium sulfate solution at the corrosion potential (Ecorr) was investigated by using electrochemical impedance spectroscopy (EIS), environmental scanning electron microscopy (ESEM), energy dispersive X‐ray spectroscopy (EDS) and X‐ray diffraction (XRD). The results showed that the corrosion of AZ91D started at both the primary α‐Mg and the eutectic α‐Mg. The surface first was covered by a film (MgO, Mg(OH)2) which became thicker with time. Due to the dissolution of the eutectic α‐Mg, the concentration of aluminum increased, MgAl2(SO4)4 · 2H2O precipitated at the primary α‐Mg and progressively spread to the eutectic α‐Mg areas. The surface film changed from two‐layer to three‐layer structure with the increase of immersion time.

[1]  R. Raman.  The role of microstructure in localized corrosion of magnesium alloys , 2004 .

[2]  M. Jönsson,et al.  Atmospheric Corrosion of Magnesium Alloys: Influence of Temperature, Relative Humidity, , 2004 .

[3]  S. Mathieu,et al.  A corrosion study of the main constituent phases of AZ91 magnesium alloys , 2003 .

[4]  G. Frankel,et al.  Influence of Dichromate Ions on Corrosion Processes on Pure Magnesium , 2003 .

[5]  C. Blanc,et al.  AC Impedance Spectroscopy in Characterizing Time-Dependent Corrosion of AZ91 and AM50 Magnesium Alloys Characterization with Respect to Their Microstructures , 2001 .

[6]  M. Natta.  Evidence of Two Anodic Processes in the Polarization Curves of Magnesium in Aqueous Media , 2001 .

[7]  N. Pébère,et al.  The corrosion of pure magnesium in aerated and deaerated sodium sulphate solutions , 2001 .

[8]  W. Zhou,et al.  Evaluation of microstructural effects on corrosion behaviour of AZ91D magnesium alloy , 2000 .

[9]  G. Song,et al.  Corrosion behaviour of AZ21, AZ501 and AZ91 in sodium chloride , 1998 .

[10]  M. Dargusch,et al.  Influence of microstructure on the corrosion of diecast AZ91D , 1998 .

[11]  Noboru Masuko,et al.  Morphology and Structure of Oxide Films Formed on Magnesium by Exposure to Air and Water , 1995 .

[12]  J. Kruger,et al.  Corrosion of magnesium , 1993 .

[13]  O. Lunder,et al.  The Role of Mg17Al12 Phase in the Corrosion of Mg Alloy AZ91 , 1989 .

[14]  L. Fairman,et al.  Intergranular Stress-Corrosion Crack Propagation in Magnesium Aluminium Alloys , 1971 .