Reaction of molybdenum electrode with components in glass
Molybdenum electrodes react with certain components or impurities in the glass composition at high temperatures, causing serious corrosion to the electrodes. For example, glass solutions using As2O3, Sb2O3, and Na2SO4 as clarifiers corrode molybdenum electrodes very seriously and will be oxidized into MoO and MoS2.
Electrochemical reactions in glass electrofusion
The electrochemical reaction occurs in glass electrofusion at the contact interface between the molybdenum electrode and the molten glass. During the positive half cycle of the AC power supply, negative oxygen ions transfer to the positive electrode to release electrons, and the electrons release oxygen, causing the oxidation of the molybdenum electrode.
During the negative half cycle of the AC power supply, some cations (such as boron) in the glass melt will move toward the negative electrode and generate molybdenum electrode compounds. These compounds are loosely deposited on the electrode surface and damage the electrode.
Temperature and current density
The erosion rate of molybdenum electrodes increases with increasing temperature. When the glass composition and process temperature are stable, current density becomes the factor controlling the electrode corrosion rate. Although the maximum allowable current density of molybdenum electrodes can reach 2~3A/cm2, if large current is operated, the erosion of the electrode will increase.