Electrochemical On-Line Corrosion Monitoring

Electrochemical On-Line Corrosion Monitoring On-line corrosion monitoring is used to evaluate the status of equipment and piping in chemical process industries (CPI) plants. These monitoring methods are based on electrochemical techniques. To use on-line monitoring effectively, the engineer needs to understand the underlying electrochemical test methods to be employed. This section covers many of these test methods and their applications as well as a review of potential problems encountered with such test instruments and how to overcome or avoid these difficulties. 

ENA was recently used for remote on-line corrosion monitoring of carbon steel electrodes in a test loop of a surge water tank at a gas storage field. An experimental design and system for remote ENA and collection of electrochemical impedance spectroscopy (EIS) data (Fig. 13) have been presented elsewhere. In the gas storage field, noise measurements were compared with electrode weight loss measurements. Noise resistance (R ) was defined as... 

Continuous, on-line corrosion monitoring can be used to operate FGD systems at optimal efficiency while avoiding high corrosion rates. Conventional corrosion monitors are designed for use in bulk liquids and do not function satisfactorily in the thin condensate films that form on the surfaces of FGD ducts. Recent EPRI research has made use of an advanced electrochemical method of corrosion surveillance developed by the Corrosion and Protection Centre Industrial Services (CAPCIS) in England [30]. This method allows on-line monitoring of corrosion activity in either thin condensate films or bulk liquids. EPRI introduced the CAPCIS system to the U.S. electric utility industry in 1985, sponsoring several field demonstrations. 

Roberge PR, Sastri VS. On-line corrosion monitoring with electrochemical impedance spectroscopy. Corrosion 1994 50 744—54. 

Development of the monitoring techniques is necessary to ensure sound and efficient operation of the FUJI-MSR. Fortunately, the reactor system does not require continuous monitoring of the major fuel constituents such as Li, Be, Th, F and U [XXX-36]. Therefore, electrochemical on-line monitoring of the redox potential has been developed it is only the U /U ratio, which responds to the corrosive atmosphere and to the distribution of fission... 

Neufeld, P. and Queenan, E. D., Frequency Dependence of Polarisation Resistance Measured with Square Wave Alternating Potential , Br. Corros. J., 5, 72-75, March (1970) Fontana, M. G., Corrosion Engineering, 3rd edn., McGraw-Hill, pp 194-8 (1986) Dawson, J. L., Callow, L. M., Hlady, K. and Richardson, J. A., Corrosion Rate Determination By Electrochemical Impedance Measurement , Conf. On-Line Surveillance and Monitoring of Process Plant, London, Society of Chemical Industry (1977)... 

Dawson, J. L., Callow, L. M., Hlady, K. and Richardson, J. A., Corrosion Rate Determination By Electrochemical Impedance Measurement, Conf. On-Line Surveillance and Monitoring of Process Plant, London, Society of Chemical Industry (1977)... 

ASTM G 96, Practice for On-Line Monitoring of Corrosion in Plant Equipment (Electrical and Electrochemical Methods)—This standard outlines procedures for online corrosion monitoring in operating systems. The test methods described in this standard are used to determine the cumulative metal loss (electrical resistance method) or instantaneous corrosion rates (electrochemical method). Reference 15 provides a summary of electrical resistance and polarization resistance theory. 

G 96, Guide for On-Line Monitoring of Corrosion in Plant Equipment (Electrical and Electrochemical Methods)... 

There are many other techniques for measuring corrosion. Some of these may rely on chemical solution analysis or physical measurement of metal loss. One widely used additional technique is provided by ASTM G 96, Practice for On-Line Monitoring of Corrosion in Plant Equipment (Electrical and Electrochemical Methods). This guide covers two basic procedures. In one, a sample of the material, usually in the form of a continuous wire, is immersed into the environment of interest (liquid, air, solid, or multiphase). The electrical resistance through the wire is determined. As corrosion consumes the cross section of the wire, the resistance increases proportionately. The second procedure uses the polarization resistance technique described in ASTM G 59 to determine the corrosion rate in the environment. 

From the presented review, it is apparent that at present we do not have at our disposal a reliable and effective electrochemical technique enabling rapid and accurate determination of the corrosion current of metals in cathodic polarization conditions, although achievement of the assumed aim seems much closer. At present, there is a significant demand for such types of methods, which could be the basis of modem on-line monitoring systems of corrosion of polarized structures, and would introduce an expected technological breakthrough in the control of the effectiveness of electrochemical protection. 

Work is being carried out on new on-line monitoring systems of CP effectiveness. The start of production by some firms of complicated portable apparatus for electrochemical investigations, allowing measurements in field conditions, should be mentioned. The SOLARTRON SI 1280 corrosion monitor and Gamry Instruments apparatus can be mentioned here. The development of apparatus in this direction holds... 

Standard Guide for on-line monitoring of corrosion in plant equipment (Electrical and electrochemical methods). Annual Book of ASTM Standards. Philadelphia, Pa. American Society for Testing of Materials, 2001 03(02) G 96-90. 

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