Electrochemical production of sodium for the modification of aluminium in foundries

The sodium concentration in aluminium-silicon alloys needs to be about 100ppm for optimum strength. This is difficult to maintain because of its low solubility and high volatility. Continuous and/or automated sodium addition is desired so a new device is being developed to enable this. Suitable electrochemical devices have been under development for over 6 years. The major innovations discussed here are removing the sodium ion conducting ceramic away from the aluminium melt and combining the device with a flow degassing unit to aid mixing and dissolving of the sodium. Tests have shown that the device improves efficiency from about 20% to 50% and there is a dramatic reduction of local air pollution and running costs. Sodium sensors are needed so that the device can be automated and for improving the quality of castings. After more than 20 years there is finally sufficient interest to finalize a commercial sensor.