Measurement, corrosion

A corrosion measurement can be made without having to see or remove the test sample. 

Corrosion measurements can be made quickly—in a few hours or days, or continuously. This enables sudden increases in corrosion rate to be detected. In some cases, it will be possible then to modify the process to decrease the corrosion. 

Ion probes. Determining the level of ions in solution also helps to control corrosion. An increase in concentration of specific ions can contribute to scale formation, which can lead to a corrosion-related failure. Ion-selective elec trode measurements can be included, just as pH measurements can, along with other more typical corrosion measurements. Especially in a complete monitoring system, this can add information about the effect of these ions on the material of interest at the process plant conditions. 

A final type of measurement is the detection of localized corrosion, such as pitting or crevice attack. Several corrosion-measuring probes can be used to detec t localized corrosion. Some can detect locahzed corrosion instantaneously and others only its result. These types of corrosion may contribute little to the actual mass loss, but can be devastating to equipment and piping. Detec tion and measurement of localized corrosion is one of the areas with the greatest potential for the use of some of the newest electrochemicaUy Based corrosion monitoring probes. 

European Federation of Corrosion Publication No. 4, A WP report Guidelines on Electrochemical Corrosion Measurements, The Inst, of Metals, London (1990)... 

Bech-Nielsen, G. Automated Methods of Corrosion Measurement 31... 

Automated Methods of Corrosion Measurement Bech-Nielsen,G. Andersen, J. E. T. Reeve, J. C. Bisg rd, A. D. Nielsen, L. V. 31... 

Electric Breakdown in Anodic Oxide Films Physics and Applications of Semiconductor Electrodes Covered with Metal Clusters Analysis of the Capacitance of the Metal-Solution Interface. Role of the Metal and the Metal-Solvent Coupling Automated Methods of Corrosion Measurement... 

Measurements of corrosion rates and other parameters connected with corrosion processes are important, first as indicators of the corrosion resistance of metallic materials and second because such measurements are based on general and fundamental physical, chemical, and electrochemical relations. Hence improvements and innovations in methods applied in corrosion research are likely to benefit basic disciplines as well. A method for corrosion measurements can only provide reliable data if the background of the method is fully understood. Failure of a method to give correct data indicates a need to revise assumptions regarding the basis of the method, which sometimes leads to the discovery of as-yet unnoticed phenomena. 

The present selection of automated methods for corrosion measurements is not motivated simply by the fact that a certain measurement can be performed automatically. Automation is applied to nearly all types of... 

Corrosion measurements by titration (CMT) were first introduced in 1990. The method is based on the following considerations When a metal corrodes with no applied current in an aqueous solution, the anodic dissolution reaction... 

There is an obvious need for single, fast, and rehable corrosion measurements on metallic products, whether use in particular environments is the concern, or whether the application of a particular post-treatment necessitates a control. Various types of chamber tests are used for technical testing. These tests are accelerated, which means that the metallic items are exposed to more aggressive conditions than they are expected to meet during actual savice, but it still takes a long time to obtain a measurement. The measurement indicates the time to failure (to a certain degree or... 

Figure 3. Long-term corrosion measurement of an electrolytic Sn-Zn alloy containing 26% Zn (by weight) in a 3% NaCI solution, pH = 4.000, with argon bubbling through the solution. Upper diagram corrosion potential vs. time lower diagram CMT and EC measurements vs. time. After 80-100 min, the ratio CMT/BC is close to 4. (Reprinted from Ref. 2, with kind permission from Elsevier Science Ltd., Kidlington, Oxfmd, UK.)...

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