Development of electrochemical techniques to study oxide films on construction materials in high temperature water

Electrochemical measurements in BWR coolants are complicated due to the low conductivity of the water. To obtain useful information, a technique based on thin-layer electrode arrangement has been introduced. This technique enable one to perform electrochemical impedance, voltammetric and other electrochemical measurements even in high purity water. Combining these results with measurements of the surface resistance of the oxide film using the contact electric resistance (CER) technique enables more detailed studies of oxide growth mechanisms and of the influence of water chemistry on oxide properties. Examples are given on impedance and CER measurements of the oxide film forming on AISI 316L stainless steel in high temperature low conductivity water. The results indicate that the oxide film forming on AISI 316L in BWR water during short exposure times is a good electronic conductor, and that its impedance spectrum is clearly influenced by the oxygen content of the water. In addition, the newest modifications of the thin layer electrode arrangement are discussed. (author)