Electrochemical reactions of Al3+ and formation mechanism of Al-W intermetallic compound on tungsten electrode were investigated by means of cyclic voltammetry and theoretical calculation analysis. Al3+ was reduced to Al metal in a single step and the deposition potential of sodium was more negative than aluminum in molten cryolite system. In both Na3AlF6-Al2O3 system and Na3AlF6-Al2O3-LiF system

the deposition reaction of Al3+ as Al-W intermetallic compounds on tungsten electrode was quasi-reversible

involving diffusion process from the sweep rate range of 50 mV·s-1 to 150 mV·s-1. During the forming process of Al-W intermetallic compound

Al3+ diffusion coefficient increased from 4.54×10-9 cm2·s-1 to 5.71×10-9 cm2·s-1

and reaction activation energy decreased from 11.14 kJ·mol-1 to 10.47 kJ·mol-1. Al-W intermetallic compound was insoluble in both Na3AlF6-Al2O3 system and Na3AlF6-Al2O3-LiF system. In Na3AlF6-Al2O3-LiF system

Li did not deposit out on tungsten electrode during the reduction process and oxidation current was larger than that in Na3AlF6-Al2O3 system during the formation process of Al-W intermetallic compound. In the constant current electrolysis experiment

XRD

SEM

EDS showed that Al-W intermetallic compound was insoluble in molten salt

but adhered to the surface of the working electrode. Adding LiF decreased Al-W intermetallic compound (WAl4) quantity but increased Al2O3 quantity. With the formation of Al-W intermetallic compound

Li-Al intermetallic compound also formed at the same time and it was soluble in Na3AlF6-Al2O3-LiF system. It confirmed that the working electrode was more stable during the electrolysis process after adding LiF. LiF inhibited the growth of WAl4 and increased the activity of Al3 + in Na3AlF6-Al2O3-LiF system. As the cathode of aluminum electrolysis

alloying effect was obvious on tungsten electrode during the electrolysis process. In order to guarantee normal electrolysis

tungsten wire electrode should be pretreated to form a stable alloy.