Electrochemical Test Methods

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. 

Wedge test results suggest that the curing process (e.g., percent crosslinking) of the epoxy-polyamide primer system is not affected by the addition of organosilanes, but may be affected by NTMP. The results of substrate surface characterization, adsorption behavior of applied films, and evaluation of candidate inhibitors by chemical, mechanical, and electrochemical test methods are presented. Mechanisms to explain the observed behavior of the various phosphonate and silane polymer systems are discussed. 

Thompson, N.G., Payer, J.H., DC Electrochemical Test Methods, in Corrosion Testing Made Easy, B.C. Syrett (ed.), NACE International, Houston, TX, USA, pp. 72-77, 1998. 

Refs. [i] StrehblowHH (2006) Conventional electrochemical test methods. In Czichos H, Saito T, Smith L (eds) (2007) Springer Handbook of Materials Measurement Methods. Springer. Part D, 12.1 Corrosion, pp 615-639... 

Since atmospheric corrosion is an electrochemical process, attempts have been made to develop electrochemical test methods that can predict the corrosion resistance of the coating-substrate system [9.41], [9.42],... 

By means of specially designed single or multi electrode probes many electrochemical test methods can, in principle, be implemented in plant, pilot testing facilities or natural environments. 

Immersion tests provide no information about reaction mechanisms and often they require relatively long exposure times. Electrochemical tests do not have these drawbacks and they are therefore widely used in practice. In the following electrochemical polarization methods are presented that provide information on the rate of uniform corrosion under conditions where the rate is controlled by charge-transfer. Other electrochemical test methods will be presented in subsequent chapters. 

One simple way of determining an appropriate scan rate is to use a scan rate slow enough so that if the scan is stopped (and the applied potential or current is maintained constant), the current does not decrease with time under a potential controlled scan, nor does the potential continue to shift under a current controlled scan. A little trial and error will determine the optimal scan rate. Often times it can be much faster than 0.6 V/h, especially in well-aerated, flowing solutions. Under quiescent conditions with oxidized materials, the necessary scan rate is much slower than 0.6 V/h. A detailed discussion on effects of scan rate, ohmic voltage error, choice of over-potential, and other factors appears in the chapter on electrochemical test methods in this manual. 

Lagerberg, S., Bernhardsson, S., and Lau, P., Electrochemical Testing Methods for the Study of Localized Corrosion, 10th Scandinavian Corrosion Congress, Swedish-Corrosion Institute, Stockholm, Sweden, 1986, pp. 271-277. 

Siebert, O. W., Laboratory Electrochemical Test Methods, Laboratory Corrosion Tests and Standards, ASTM STP 866, G. S. Haynes and R. Bahoian, Eds., ASTM International, West Conshohocken, PA, 1985, pp. 65-90. 

Several electrochemical tests have been used successfully over the years to estimate the corrosion behavior of a given metal in soil or to determine the soil corrosivity. These tests can be carried out in water extract of soil and/or in water saturated soil, when all dissolved salts (ions) are present. The electrochemical test methods and practices are described in several ASTM Tests Methods and Practice ... 

Electrochemical test methods evaluate various corrosion characteristics of metals and alloys in a relative short time. Among these characteristics that can be evaluated electro-chemically are ... 

Morales A., Ajona J.I. Durability, performance and scalability of sol-gel front surface mirrors and selective absorbers. J. Phys. IV France 1999, 9 513-518 Murray J.M. Electrochemical test methods for evaluating organic coatings on metals an update. 

Stimulation Electrode Materials and Electrochemical Testing Methods... 

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