The effect of indium addition on the corrosion behavior of AP65 Mg alloy was examined. The indium modified AP65 exhibits accelerated pitting corrosion and overall corrosion, but there is almost no incubation period at the onset of corrosion. Polarization curve measurements indicate that the indium modified AP65 has more negative corrosion potential, which is an improvement aspect of the electrochemical activation. The corrosion current density increases from 0.126 to 0.868 mA/cm2 with and without 2.0% (mass fraction) indium addition. The mean potentials of AP65 negatively shift from -1.491 V to -1.584 V by adding 2.0% indium. The effect of indium addition on the corrosion performance of AP65 seems to be associated with the decrease of cathode-to-anode area ratio of the alloy, which may change the electrochemical anode and cathode polarization behavior of the alloy.
Magnesium is a promising metal used as anodes for chemical power sources. This metal could theoretically provide negative discharge potential and exhibit large capacity during the discharge process. However, when the magnesium anode is adopted for practical applications, several issues, such as the discharge products adhered to the electrode surface, the self-discharge occurring on the anode material, and the detachment of metallic particles, adversely affect its inherently good discharge performance. In this work, the types of chemical power sources using magnesium as anodes were elaborated, and the approaches to enhance its anode performance were analyzed.
The effects of Hg and Ga on the electrochemical corrosion behaviors of the Mg-2%Hg, Mg-2%Ga and Mg-2%Hg-2%Ga (mass fraction) alloys were investigated by measurements of polarization curves, galvanostatic tests and measurements of electrochemical impedance spectroscopy. Scanning electron microscopy, X-ray diffractometry and energy dispersive spectrometry were employed to characterize the microstructures and the corroded surface of the above alloys. The results demonstrate that the microstructure of the Mg-2%Ga alloy is solid solution and the Mg-2%Hg and Mg-2%Hg-2%Ga alloys have white second-phases at the grain boundaries. The Mg-2%Ga alloy has the worst electrochemical activity and the best corrosion resistance, showing a mean potential of -1.48 V and a corrosion current density of 0.15 mA/cm2. The Mg-2%Hg-2%Ga alloy has the best electrochemical activity and the worst corrosion resistance, showing a mean potential of -1.848 V and a corrosion current density of 2.136 mA/cm2. The activation mechanism of the Mg-Hg-Ga alloy is dissolution-deposition of the Hg and Ga atoms.
Mg-Al-Pb alloy is one of the newly developed materials for the seawater activated batteries. As-cast Mg-6Al-5Pb and Mg-6Al-5Pb-0.5Mn alloys with different additions of Al-15%Mn （mass fraction）, Al-30%Mn and Al-50%Mn master alloys were prepared by melting and casting. Their microstructures were observed by optical microscopy and scanning electron microscopy. The electrochemical properties, hydrogen evolution and mass loss of Mg-6Al-5Pb-0.5Mn alloys were studied. The results show that Mg-6Al-5Pb-0.5Mn alloy added with Al-50%Mn master alloy provides more negative corrosion average potential （-1.66 V）, smaller corrosion current density （7 μm/cm2） and lower free corrosion rate （0.51 mg·cm-2·h-1） than other alloys. This is probably attributed to the presence of Al11Mn4 phase, which facilitates the self-peeling of corrosion products and enlarges the electrochemical reaction area as well as enhances the electrochemical activity.
The influence of Ga and In on the electrochemical properties of Mg anode materials were investigated by the polarization and galvanostatic curve tests. The microstructure and the corroded surface of the Mg-In-Ga alloys were observed by scanning electron microscopy （SEM）. The corrosion product of the Mg-0.8%In （mass fraction） and Mg-0.8%Ga-0.3%In alloy were determined by X-ray diffraction. The results show that no second phase exists in the Mg-xIn （x=0-0.8%） allloys. Intergranular compounds containing Ga and In elements occur in the Mg-0.8%In-xGa （x=0-0.8%） alloys. The addition of In into Mg as well as the addition of 0.05%-0.5%Ga into Mg-In alloy promotes the corrosion resistance. The addition of Ga into Mg-In alloys also promotes the electrochemical activity. The Mg-0.8%In-0.8%Ga alloy has the most negative mean potential,-1.682 V, which is more negative than -1.406 V in AZ91D. The corrosion type of the Mg-In-Ga alloys is general corrosion and the corrosion product is Mg（OH）2.
Aluminum is an innovative anode material for seawater battery. But large polarization and low electrochemical activity restrict its application. In this research, A1-Mg-Sn-Hg-Ce anode materials were prepared and the microstructures were investigated by scanning electron microscopy （SEM）. The electrochemical properties of A1-Mg-Sn-Hg-Ce anode materials were measured by potentiodynamic polarization and potential-time discharge in a 4.5 wt.%NaOH solution at 353 K. The results indicated that the increasing content of cerium addition refined the grain structure of A1-Mg-Sn-Hg alloy and promoted the uniform distribution of Sn and Hg elements in A1 matrix. The morphology of second phases changed from disperse granular to intergranulate strip with the increasing content of cerium addition in AI-Mg-Sn-Hg alloy. During the half-cell tests at a 650 mA/cm3 current density, the discharge activity of AI-Mg-Sn-Hg-Ce alloy was improved with the increasing content of cerium addition. The average discharge potential of AI-Mg-Sn-Hg-0.3 wt.%Ce alloy was -1.721 V （vs. SCE）, which was more negative than -1.406 V （vs. SCE） in AZglD. The best corrosion resistance occurred in A1-Mg-Sn-Hg-0.05 wt.%Ce alloy with the corrosion current density, 18.84± 2.21 mA/cm2. The corrosion behaviours of A1-Mg-Sn-Hg-Ce alloys were also analyzed.
