Correlation of Process Data and Electrochemical Noise to Assess Kraft Digester Corrosion: Spring Grove Experiment

摘要

Electrochemical noise (ECN) probes were deployed in a carbon steel continuous kraft digester at four locations and at one location in the bottom cone of the associated flash tank. The probes consisted of carbon steel electrodes, representing the vessel construction material, and 309LSi stainless steel overlay electrodes, representing the weld overlay repair in a portion of the vessel. Current and potential noise, the temperature at each probe location, and the value of about 32 process parameters (flow rates, liquor chemistry, etc.) were monitored continuously for a period of almost one year. Historical vessel inspection data and post-test evaluation of the probe components were used to assess/compare ECN corrosion activity with physical changes in wall thickness and corrosion patterns on the digester shell. In addition, attempts were made to correlate ECN activity from each electrode type with process parameters.