CMSE2015

Field Application of Electrochemical Noise (EN) Corrosion Monitoring Systems in the Process Industries
Dr. William M. Cox
Editor of Anti-Corrosion Methods and Materials Director and Principal Consultant, Corrosion Management Limited, UK
It is now more than thirty years since the electrochemical noise analysis was proposed for the monitoring of corrosion phenomena, yet there is still a degree of contention over its efficacy and reliability. In substantial measure, this has been due to misunderstanding and misapplication of the technology, even by respected practitioners and academics, as well as to a degree of hostility from established suppliers of traditional instrumentation. EN instrumentation has a unique capacity to operate satisfactorily in circumstances where conventional equipment is unusable. It also has an unmatched capability to detect and quantify localized corrosion phenomena such as pitting attack, stress corrosion cracking, corrosion fatigue and stress-assisted IGA. The use of electrochemical noise instrumentation to provide an indication of the cumulative rate of attack, in a manner that is similar to the approach when using traditional corrosion monitoring systems, is to overlook its most powerful capability, however, which is its capacity to provide a highly sensitive indication of the onset of attack, enabling timely and effective remedial action to be taken, thereby reducing both the duration and severity of damage. Example applications will be drawn from field installations to monitor environmentally-assisted cracking in chemical process and high purity water systems, for condensing environments in the fossil power generation and nuclear reprocessing applications and in high temperature service such as for radiant and superheater tubes in waste-to-energy and oxy-fuel combustion conditions. Particular attention will be paid in respect of specific precautions that need to be taken when utilizing EN instrumentation in process plant applications. The paper will consider a strategic approach to corrosion monitoring, corrosion surveillance and, ultimately, corrosion management. The role of modern instrumentation in augmenting condition management systems and complementing and enhancing risk-based methods of process plant operation, inspection and maintenance also will be covered.