The corrosion behavior of pure aluminum in inhibited and uninhibited 4 M KOH was investigated by means of hydrogen collection, polarization curve measurement and electrochemical impedance spectroscopy (EIS). The results showed that the corrosion of pure aluminum was greatly inhibited by the addition of ZnO and dimethyl amine epoxy propane (designated as DE). EIS and EDAX analyses revealed that ZnO produces its effect by depositing on the aluminum surface, which increases the overpotential of hydrogen evolution. It was also found that the addition of DE could greatly improve the deposition of zinc layers.

The corrosion and electrochemical behaviors of pure aluminum in KOH-ionic liquid-water solutions with variable volume ratios of water and the ionic liquid 1-butyl-3-methyl imidazolium tetrafluoroborate (BMIMBF 4 ) were for the first time investigated by means of hydrogen collection, polarization curve, galvanostatic discharge, and electrochemical impedance spectroscopy (EIS). The results of hydrogen collection experiments showed that aluminum has a low corrosion rate in KOH-BMIMBF 4 -H 2 O solutions, and the corrosion rate decreases with increase in BMIMBF 4 content in the electrolytes. The results of electrochemical experiments revealed that aluminum is electrochemically active over a very wide potential window in the KOH-BMIMBF 4 -H 2 O solutions, and its electrochemically kinetic mechanism is similar to that in the corresponding aqueous solution; the increase in KOH and water contents in the electrolytes may improve the anodic dissolution performance of aluminum. It was found that aluminum presents excellent galvanostatic discharge performance in the 2.0 M KOH BMIMBF 4 -H 2 O mixed solution with 60% water.

The corrosion and electrochemical behavior of aluminum in inhibited and uninhibited 4 M KOH-methanol-water mixed solutions with a methanol/water volume ratio of 3:2 were investigated by means of hydrogen collection, polarization curve, galvanostatic discharge, and electrochemical impedance spectroscopy (EIS). The results of hydrogen collection and electrochemical experiments showed that the addition of ZnO can obviously inhibit the corrosion of aluminum in the 4 M KOH-methanol-water solutions, and its inhibition effect can be enhanced in the hydroxytryptamine (HT)-containing KOH solution. The results of scanning electron microscopy (SEM) and energy dispersive analysis of X-ray (EDAX) revealed that ZnO produces the inhibition effect by the formation of a zinc-containing deposit layer on the surface of aluminum, and the cooperative effect of ZnO and HT may improve the deposit of zinc. The results of galvanostatic discharge indicated that aluminum can present good electrochemical activity in the 4 M KOH-methanol-water solution with 0.2 M ZnO and 1.0 mL/L HT.

Al-substituted ␣-Ni(OH) 2 coprecipitated with the additives Mg 2ϩ and Co 2ϩ was prepared by a complexation-coprecipitation method. The physical properties of Al-substituted ␣-Ni(OH) 2 samples containing different amounts of Mg 2ϩ or Co 2ϩ were examined by X-ray diffraction, AES and ICP. The effects of Mg 2ϩ and Co 2ϩ on the electrochemical performance of Al-substituted ␣-Ni(OH) 2 such as charge-discharge and diffusion coefficient of the proton (D Hϩ ) measured by current pulse relaxation and cycle life were investigated. The results show that the addition of Mg 2ϩ increases the crystal cell parameters and the charge and discharge potentials and decreases the electrochemical polarization. A higher charge efficiency and cycle life are obtained by the addition of Co 2ϩ . The addition of both Mg 2ϩ and Co 2ϩ improves D Hϩ and the stability in alkaline solution at high temperature. The D Hϩ and R t of ␣-Ni(OH) 2 electrode reach their maximum and minimum values at about 50% depth of discharge ͑DOD͒ and 75% DOD, respectively. Nickel hydroxide has received increasing attention in recent years on account of its wide use as the positive electrode material of all nickel-based alkaline secondary batteries. It exists in two polymorphic forms, ␣-and ␤-Ni(OH) 2 , which transform to ␥-NiOOH and ␤-NiOOH, respectively, on charging. 1 A larger specific capacity is expected for the ␣-Ni(OH) 2 /␥-NiOOH couple because the oxidation state of nickel in ␥-NiOOH is 3.67 or 3.3-3.7, 2,3 compared with the ␤-Ni(OH) 2 /␤-NiOOH couple. Moreover, there are no volume expansion and mechanical deformation problems during overcharging or a long period of float charging in the ␣-Ni(OH) 2 /␥-NiOOH system; whereas, these problems exist in the ␤-Ni(OH) 2 /␤-NiOOH couple, limiting the further improvement of ␤-Ni(OH) 2 . However, ␣-Ni(OH) 2 is unstable in alkaline medium or at high temperature and transforms to ␤-Ni(OH) 2 . 1 More attention has been paid to synthesizing stabilized ␣-Ni(OH) 2 by partial substitution of other cations such as Co, 4 Al, 5-10 Fe, 11 Mn, 12 and Zn 13,14 for Ni to increase the stability of the ␣-phase structure in strong alkaline medium. Among these, Alsubstituted ␣-Ni(OH) 2 is most attractive because of its high electrochemical performance and structural stability. Kamath et al. 5 chemically prepared the Ni/Al-layered double hydroxides with a specific discharge capacity of 240 mAh g Ϫ1 and a half-discharge potential of 350 mV ͑vs. Hg/HgO͒ for a 20 mol% Al-containing compound. Dai 10 reported that ␣-Ni(OH) 2 stabilized by 15 mol% Ni substitution with Al can maintain the basic ␣-phase structure, and the crystallites become larger or crystallinity increases during the charge-discharge cycles even in the overcharge condition. Wang 9 also reported that Al-substituted ␣-Ni(OH) 2 is stable in strong alkaline medium even after 100 electrochemical cycles when the content of Al reaches 15.7 mol% and a recrystallization process occurs both during the alkaline aging treatment and charge-discharge cycling, which causes growth of crystallin...

The effects of zinc oxide and/or polyethylene glycol (PEG) as electrolyte additives on the corrosion and electrochemical performances of pure aluminum in 4.0 M KOH solutions were investigated by means of hydrogen collection, polarization curve, galvanostatic discharge, scanning electron microscopy (SEM), and energy dispersive analysis of X-ray (EDAX). The addition of ZnO markedly inhibited the corrosion of aluminum in 4.0 M KOH solutions, resulting from the deposition of zinc with high hydrogen evolution overpotential in aluminum surfaces. The introduction of PEG in the alkaline zincate solution obviously improved the deposition of zinc by increase in the overpotential of zinc deposition, thus the corrosion rate of aluminum in the alkaline zincate solutions with PEG was further decreased. The enhancement effect of PEG on the inhibition of zinc oxide first increased and then decreased with increasing the content of PEG in the electrolyte. The electrolyte system with 0.2 M ZnO and 2.0 mM PEG presented the highest inhibition efficiency (98.8%) for the corrosion of aluminum. The results of galvanostatic discharge indicated that the aluminum anode shows excellent discharge performances in the 4.0 M KOH solution with 0.2 M ZnO and 2.0 mM PEG.