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 testing 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.