电流密度对熔盐电镀铝晶粒形貌的影响

结合扫描电镜形貌观察和能谱分析研究了AlCl3-NaCl-KCl低温无机熔盐体系中电镀铝时电流密度对Q235钢基体上铝晶粒沉积形貌的影响,并从铝晶粒沉积过程中总的自由能变化的角度对其析出规律进行探讨。结果表明,在由80%AlCl3+10%NaCl+10%KCl所组成的熔盐中,当温度为150℃、电流密度为20.0～98.7 mA/cm2范围内电镀时,均可在Q235钢表面上获得完整、致密的铝镀层。电流密度的大小直接影响铝晶粒的形态和尺寸。电流密度低时,铝晶粒呈片状;电流密度高时,铝晶粒呈颗粒状,且随电流密度的增大,铝晶粒尺寸呈现减小趋势。结合热力学和动力学探讨了电流密度大小对电镀铝晶粒尺寸及形貌的影响。电流密度对铝晶粒形貌的影响与铝晶粒在Q235钢基体上沉积时形核及长大过程中的总自由能变化,特别是由电流密度大小所决定的铝晶核析出电化学能的大小有关。

Effect of current density on morphology of electrodeposition aluminum crystal from molten salts

Effect of current density on morphology of aluminum crystals electrodeposited on Q235 steel substrate from AlCl3-NaCl-KCl molten salt was investigated by SEM observation and EDS analysis.The precipitation of aluminum crystal was theoretically discussed from the standpoint of total free energy varying in the deposition process of aluminum crystals.The results show that,the uniform and compact aluminum layer can be obtained by electrodeposition at temperature of 150 ℃ with current density in the range of 20.0-98.7 mA/cm2 in 80%AlCl3+10%NaCl+10%KCl molten salt.The current density plays a vital role in the morphology and size of aluminum crystals.At low current density,the aluminum crystals take on flake-like shape,while at high current density,they become spherical.Meanwhile the size of aluminum crystals decreases with increasing the current density.Combined thermodynamics and kinetics,the effect of current densities on the size and morphology of aluminum crystals was discussed.The effect of current density on the morphology of aluminum crystals is related to the change of total free energy during the nucleation and growth of aluminum crystals deposited on Q235 steel,especially the magnitude of precipitation electrochemical energy which is determined by current density.