铝酸盐及添加剂对铝阳极电化学性能的影响

为了扩大铝阳极的应用范围,采用添加剂来降低其腐蚀速度,同时活化铝阳极.用塔菲尔曲线、线性扫描伏安法、恒电流放电等方法,研究了在4 mol/L KOH溶液中,NaAlO2及添加剂NaF对铝(99.999%)阳极电化学性能的影响.结果表明:NaAlO2对铝阳极有害,NaAlO2的浓度不要超过3 mol/L;但添加50 mmol/L NaF在3.5 mol/L NaAlO2 4 mol/L KOH中,则铝的腐蚀电流密度由23.7 mA/cm2降低到20.8 mA/cm2,电极电位由-0.75 V负移到-1.50 V,开路电位由-1.64 V负移到-1.68 V,电位滞后时间缩短,基本上恢复到铝在4 mol/L KOH溶液中的电化学性能.

Effects of NaAlO2 and Additives on Electrochemical Behavior of Aluminum in Alkaline Solution

With a view to the decreasing of the corrosion rate and activation of aluminum anode by some additives, the effects of NaAlO_2 and additive NaF on the electrochemical properties of aluminum ( 99.999%) anode in a 4 mol/L KOH solution were studied using Tafel curves, linear scanning voltammetry and constant current discharge curves. The results indicated that NaAlO_2 was harmful to the aluminum anode, and it could be imperative to keep the concentration of NaAlO_2 below 3.0 mol/L. When NaF was added into the mixed solution of 3.5 mmol/L NaAlO_2 plus 4 mmol/L KOH at a concentration of 50 mmol/L, the corrosion current density (J_ corr) of the aluminum decreased from 23.7 mA/cm~ 2 to 20.8 mA/cm~ 2, the electrode potential shifted from -0.75 V to -1.50 V, the open circuit potential E_ ocp shifted from -1.64 V to -1.68 V, and the potential lag time decreased as well. This was essentially the same as those for the aluminum in 4 mol/L KOH solution, indicating that the additive NaF was capable of retaining the electrochemical properties of the Al alloy in the NaAlO_2 solution of a quite high concentration.