Reference Electrodes in Acid and Base Systems

Several electrodes were screened for possible use as reference electrodes for anodic corrosion control systems. Mercury- mercury salts, noble metal-noble metal oxides and molybdenum-molybdenum oxide were examined extensively and found to be useful reference electrodes in sodium hydroxide and phosphoric acid. A chromium carbide electrode was found to be a useful reference electrode in sodium hydroxide. The emf of these electrodes as a function of concentration and of temperature is described. The emf behavior of the noble metal-noble metal oxides in chromic acid cleaning solution and the emf of stainless steel in nitric acid are described briefly.