Control of the near-surface OH concentration of float glass by anodic proton injection

Controlling the OH concentration near the float glass surface was investigated via anodic proton injection into a glass melt under conditions simulating the float glass process. A DC voltage of 1-4 V was applied to the glass at 1000°C between the molten tin as an anode and graphite placed on the glass as a cathode. Although the OH concentration of the glass near the glass/tin interface was controlled to the same level as that in the interior of the glass when a DC voltage of 3 V was applied, the decrease in Na concentration, one order of magnitude greater than the amount of injected protons, was observed around the glass/tin interface. Therefore, the OH concentration by dehydration cannot be restored using anodic proton injection without substantial composition change. Tin was observed to be electrochemically injected into the glass when a DC voltage of >4 V was applied, and majority of the injected protons were released from the glass under the experimental conditions. Finally, the conditions that achieved an OH concentration near the glass/tin interface matching with that in the interior of the glass without substantial composition change around the anode are discussed and proposed.