铝及Al-Mg-Zn-Cd合金在氯化锂的水、甲醇溶液中的阳极行为及其负差效应机理

研究了纯铝和Al-Mg-zn-Cd合金在氯化锂水溶液和氯化锂甲醇溶液中的阳极特性,探讨了负差效应的机理。合金在LiCl甲醇溶液中有较高的负电位,比纯铝的负差效应小,且其数值随LiCl浓度增加而减小。合金在酸性水溶液中的负差效应受电化学溶解过程控制。铝的阳极氧化不是一步完成的,存在着由低价态氧化为高价态的迟缓性,使得某些低价态离子(如Al~+)离开电极表面,与溶液中H_3O~+发生化学的氧化还原反应而析出氢气。该过程的可能性与电化学溶解速度成正比。

Anodic Behavior and Mechanism of Negative Difference Effect of Aluminium and Al-Mg-Zn-Cd Alloy in Aqueous and Methanol Solution of Lithium Chloride

The anodic behavior of pure aluminium and A1-Mg-Zn-Cd alloy in aqueous and methanol solution of lithium chloride has been studied. The mechanism of negative different effect is discussed. In methanol solution of LiCl, the alloy has higher negative potential and less negative different effect than pure aluminium and the negative different effect is decreased as the concentration of LiCl is increased. In acidic solution, the negative different effect of the alloy is controlled by the kinetics of electrochemical dissolution. Aluminium is slowly oxidized from lower oxidation state to higher oxidation state in the anodic electrochemical oxidation process. Therefore, certain some ions of the lower oxidation state(such as Al~+ )will diffuse from the surface of the electrode and react with H_3O~+ in the solution to evolve hydrogen. The possibility of this process is proportional to the rate of the electrochemical dissolution process.