Kuang-Tsan Kenneth Chiang and Lietai Yang
Department of Earth, Material, and Planetary Sciences
Geosciences and Engineering Division
Southwest Research Institute^®
San Antonio, TX 78238-5166, U.S.A.

  ABSTRACT

 Existing coupled multielectrode array sensors are promising devices for application as an online tool for corrosion monitoring.  However, most of these devices have an upper operating temperature limit of approximately 70 °C.  At temperatures above 70 °C, crevice formation between the electrode and the mounting material (epoxy) may result in erroneous corrosion rate measurements.  In this paper, a new electrochemical corrosion monitoring system that has high temperature (>100 °C) capability is presented.  A diamond-like carbon thin film was deposited on the sensing electrodes.  The coated surfaces exhibited high electrical impedance after tested in caustic (pH = 10) solution at 250 ^oC.  The effectiveness of the diamond-like carbon film in protecting the electrodes was demonstrated in a corrosive solution containing NaCl-NaNO₃-KNO₃ salt mixture at 150 °C.  The new corrosion monitoring system has potential application for monitoring corrosion rate for container materials in potential nuclear waste repositories and in the high temperature systems of nuclear power plants.