Abstract: Various pH sensor apparatus, and methods of providing such apparatus, include using a hydrogen ion (H+) sensitive element formed of a corrosion-resistant metal, such as titanium or zirconium. The pH sensitive element makes use of a discontinuous metal oxide layer, e.g., titanium dioxide, formed on a surface of the metal hydrogen ion (H+) sensitive element (e.g., titanium wire core element). Preferably, the discontinuous metal oxide layer is formed by thermal treatment in the presence of an oxygen containing media. The pH sensor apparatus may be used with any of a range of standard reference electrodes for providing the pH measurement. Further, a pH sensor apparatus can be used as a reference electrode with a hydrogen sensing electrode, e.g., a fine gold wire, for measuring dissolved hydrogen (H2) concentrations.