Corrosion of platinum alloy electrodes in a LiO₂–Al₂O₃–SiO₂ melt

Although platinum is known to be one of the most corrosion resistant metals, material degradation is observed when platinum alloy electrodes are in contact with glass melts. A glass melting furnace was set up in order to investigate the degradation mechanisms of platinum alloy electrodes in glass melts. This setup enables glass melting at temperatures up to 1700°C and has two water cooled electrodes immersed into the melt with a maximum current of 10 A and variable current frequencies (0–6000 Hz). The well-known LiO₂–Al₂O₃–SiO₂ glass ceramic Ceran^® was chosen for this work. The corroded platinum alloy electrodes were investigated using scanning electron microscope (SEM), energy dispersive x-ray spectroscopy (EDS), micro x-ray fluorescence analysis (μRFA), diffractometry (XRD), and inductively coupled plasma-optical emission spectroscopy (ICP-OES). It was shown that above a threshold frequency platinum alloy degradation is very strongly reduced. The dependence of corrosion on current frequencies can be explained by jump distances of ions.