AZ91D镁合金在NaHCO_3薄液膜下的腐蚀行为

Corrosion Behavior of AZ91D Magnesium Alloy Under Thin Electrolyte Layers Containing NaHCO_3

镁合金大气腐蚀的研究十分重要,而目前有关侵蚀性离子HCO_3^-在薄液膜下对镁合金腐蚀行为的研究报道较少。通过阴极极化曲线和电化学阻抗谱研究了AZ91D镁合金在NaHCO_3薄液膜下的腐蚀行为,详细讨论了液膜厚度、NaHCO_3浓度和时间等参数的影响,并用扫描电镜(SEM)、能谱仪(EDS)和X射线衍射仪(XRD)进行了表征。结果表明:随着液膜厚度的降低,阴极和阳极过程均受到限制,AZ91D镁合金腐蚀速率变小;NaHCO_3浓度增加会加剧AZ91D在薄液膜下的腐蚀;浸泡24.0 h后,本体溶液中腐蚀表现为均匀腐蚀,主要腐蚀产物为MgCO_3和Al_2O_3,而薄液膜下则表现为局部腐蚀,主要腐蚀产物为MgCO_3,Al_2O_3,MgCO_3·2H_2O和Mg_5(CO_3)_4(OH)_2·5H_2O。

The corrosion behaviors of AZ91 D magnesium alloy under thin NaHCO3 electrolyte layers （TEL） were studied by cathodic polariza- tion curve and electrical impedance spectroscopy （EIS）, and the influences of thin electrolyte layer thickness, NaHCOz concentration and immerse time were discussed in detail. In addition, the corrosion behaviors were characterized by scanning electron microscopy （ SEM）, energy dispersive spectrometry （EDS） and X-ray diffractometer （XRD）. Results showed that with the decrease of TEL thickness, both the cathode and anode reactions were suppressed, and the corrosion rate of AZ91D magnesium alloy declined. Increasing the NaHCO3 concentration could accelerate the corrosion of AZglD under thin electrolyte layer. After immersed for 24.0 h, the corrosion morphologies of alloy in bulk solution and TEL were uniform corrosion and localized corrosion respectively, and the main corrosion products were respectively as follows： MgCO3 and Al2O3; MgCOa,Al2O3, MgCO3 · 2H2Oand Mg5（CO3）4（OH）2 · 5H2O.