Real time localized corrosion monitoring in industrial cooling water systems

Localized corrosion, such as pitting and crevice/underdeposit corrosion, is responsible for the majority of plant equipment corrosion failures. However, the assessment of localized corrosion in plant operating conditions is often overlooked, partly due to the fact that none of the techniques commonly used today can provide realistic and effective monitoring of localized corrosion. Research carried out has resulted in the development of the Localized Corrosion Monitor (LCM) as a solution to this problem. The LCM is based on a new and patented electrochemical method capable of in situ on-line determination of underdeposit corrosion rates. Experimental results have shown that the LCM technique can be used to determine the rate of propagation of localized corrosion in mild steel accurately and reliably. It is ideally suited to monitor the performance of corrosion inhibition programs in industrial systems. In this paper, the scientific principles behind the LCM will be described. The usefulness of the LCM will be demonstrated by the results obtained in two refinery cooling water system trials. The results demonstrate clearly that the LCM localized corrosion rate is far more sensitive to process variable changes than general corrosion rate and real time on-line localized corrosion monitoring is most effective for treatment optimization to minimize the damaging effects of process variations.