Method of measuring metal loss from equipment in process systems. Probes installed for monitoring of erosion and/or corrosion (metal loss) in process equipment use results from resistivity measurements in a measurement element and a reference element to produce a measurement of metal loss in the measurement element exposed to process flow and may trigger an alarm when measured metal loss exceeds a threshold level. Prior art methods produce numerous false alarms hiding true alarms. The present method ignores these false alarms by calculating confidence measures that are included in the metal loss calculations to attenuate noise that otherwise would produce false alarms or misinterpretation of the corrosion or erosion state in the process equipment being monitored