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Study on electrodeposition of Al-Mn alloys in ionic liquids

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Tutor: HuaYiXin
School: Kunming University of Science and Technology
Course: Non-ferrous metallurgy
Keywords: BmimCl-AlCl3-MnCl2ionic liquid,electrodeposition,Al-Mn alloy,Al-Mn-Ti alloys,cor
CLC: TG146.21
Type: Master's thesis
Year:  2013
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Abstract:
Al-Mn alloys have an excellent corrosion resistance and decorative property, it can be electroplated on steel and other materials to improve the corrosion resistance. In this paper, the BmimCl-AlCl3-MnCl2ionic liquid is used as the electrolyte for the electrodeposition of Al-Mn and Al-Mn-Ti alloy.The mechanism of electrodeposition of Al-Mn and Al-Mn-Ti alloy has been investigated systematically by cyclic voltammetry, chronamperometry measurements, etc.Electrochemical analysis shows that equilibrium electrode potential of Mn is close to Al in the BmimCl-AlCl3-MnCl2ionic liquid, which provides the foundation on codeposition of Al-Mn alloy.The cathodic electrode pocess is a qusai-reversible process.By comparing the cyclic voltammetry curve, in can be observed that the reduction peak current density reduces sharply when TiCl4is added into the BmimCl-AlCl3-MnCl2ionic liquid, however, there is no obvious change on reduction peak current density by anodic dissolution titanium electrode. Therefore, it is advisable to introduce titanium ions into the ionic liquid by making use of titanium as the anode.Electrodeposition of Al-Mn alloy experiment shows that the Mn content increases in the alloy with the increase of current density and MnCl2content in the BmimCl-AlCl3-MnCl2ionic liquid. However, with the increase of the content of and current density, current efficiency increases initially but decreases at last. When the current density is15mA/cm2, MnCl2content is1.25%, the highest current efficiency (96.8%) can be obtained. XRD shows that when the content of Mn below8.7at%, peaks can be observed that are all consistent with fcc Al(Mn) solid solution reflections. When the content of Mn is between15.3at%-26.8at%, a single amorphous phase alloy is obtained. Al-Mn alloy surface morphology depends on the Mn content in the alloy.The surface of the obtained pure aluminum coating is acicular, while the Al-Mn alloy coatings is spherical.With the increase of Mn content, the obtained crystal is fined.Al-Mn-Ti alloy is electrodeposited successfully in the BmimCl-AlCl3-MnCl2ionic liquid by making use of the titanium as the anode. Ti content in the Al-Mn-Ti alloy and current efficiency show a trend of decrease at last after the increase initally with the increase of current density, temperature and MnCl2content. When the current density is5mA/cm2, the temperature is90¡æand MnCl2content is0.63%, the highest content of Ti (5.3at%)can be obtained.At low current density, MnCl2content and temperature, smooth, bright and finer particle size of Al-Mn-Ti alloys can be obtained.Corrosion resistance experiments demonstrate that compared with Al and Al-Ti alloy, Al-Mn and Al-Mn-Ti alloy show a good corrosion resistance. Al-Mn alloy with an amorphous phase is more resistant than Al-Mn alloy with fcc Al (Mn) solid solution reflections. The corrosion resistance of Al-Mn-Ti alloy depends on the content of Ti.The high content of titanium in Al-Mn-Ti alloys does not play a positive role in the corrosion resistance. On the contrary, the addition of a small amount of Ti to the related Al-Mn alloys can apparently improve corrosion resistance compared with Al-Mn alloys.
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