A new type of hydrogen sensor for molten metals usable up to 1600 K

In order to simplify the structure of the galvanic cell-type hydrogen sensor using α-alumina as a solid electrolyte, the availability of employing air as the reference was checked by measuring the electromotive force (emf) of a gas concentration cell in the temperature range from 1073 to 1573 K. The emf was found to depend only on the hydrogen activity of the working electrode when air of normal humidity was used as the reference gas.The hydrogen activities in molten copper melted in a closed chamber were measured by immersing this structure-type hydrogen sensor at 1423 K. The measured values agreed with the hydrogen activities of the molten copper produced by supplying a H2/Ar gas mixture over the surface of the melt. The performance of the hydrogen sensor was also tested for molten copper melted in the open air. Reasonable emf responses were obtained by the melt treatments such as the enrichment of hydrogen by covering the surface with charcoal or the reduction of hydrogen by exposing the surface to air.These results suggest that this type of hydrogen sensor is currently the best one for the real time detecting of the amount of hydrogen in molten metal up to 1600 K.