Abstract
Existing coupled multielectrode array sensors (CMAS) with epoxy insulation are promising devices for application as online tools for corrosion monitoring. However, most of these devices have an upper operating temperature limit of approximately 70 °C. The sensor has an array of electrodes made from the metallic material of interest. The electrodes are electrically insulated from each other with a paint or mounting material (epoxy) but coupled by an external circuit and arranged so that a small area of the electrode contacts a corrosive environment. However, epoxy and paint are strongly affected by temperature and may degrade at high temperatures. In this paper, corrosion monitoring using coated aluminum and nickel-based Alloy 600 electrodes at temperatures above 100 °C is presented. A diamond-like carbon thin film was deposited on the sensing electrodes. The effectiveness of the diamond-like carbon film in protecting the aluminum and Alloy 600 electrodes in a saturated solution containing a NaCl-NaNO3-KNO3 salt mixture at 128-141 °C was demonstrated. The effective corrosion monitoring capability of the new electrochemical sensors at high temperatures was attributed to the high corrosion-resistance properties of the diamond-like carbon film that prevented crevice formation between the aluminum and Alloy 600 electrodes.
