Spectroscopic methods corrosion

Bullock, K. R., Electrochemical and Spectroscopic Method of Characterising Lead Corrosion Films , J. Electroanal. Chem., 222, 347-366 (1987)... 

Met. = Method. C = chronocoulometry, CC = corrosion current method, EC = Electrocapillary method, EL = Ellipsometric method, IR = Infrared spectroscopic method, CV = cychc voltammetry, RT = Radiotracer method, T = Tensammetry, TF = Thin film resistance, WL = weight loss method. When a combination of methods was used aU methods are listed separated by slashes. See also list of symbols. 

In situ methods permit the examination of the surface in its electrolytic environment with application of the electrode potential of choice. Usually they are favored for the study of surface layers. Spectroscopic methods working in the ultra high vacuum (UHV) are a valuable alternative. Their detailed information about the chemical composition of surface films makes them an almost inevitable tool for electrochemical research and corrosion studies. Methods like X-ray Photoelectron Spectroscopy (XPS), UV Photoelectron Spectroscopy (UPS), Auger Electron Spectroscopy (AES) and the Ion Spectroscopies as Ion Scattering Spectroscopy (ISS) and Rutherford Backscattering (RBS) have been applied to metal surfaces to study corrosion and passivity. 

If the goal is a mechtinistic/kinetic investigation of the corrosion process, ag lin examination of samples after field exposure in the enviromnent of interest may be the ideM. When this is not possible or practical, accelerated test methods should be used. If possible, these accelerated methods should have been previously verified to result in the same extent and mechtuiism of degradation as actutd field exposure. ElectrochemiceJ methods can often provide important mechanistic/kinetic information about a corrosion process. Surface m j3rtical, metcJlographic, or spectroscopic methods, or a combination thereof, can also be important components of 2my mechanistic study of metallic corrosion. 

In situ X-ray absorption spectroscopy and X-ray diffraction, as well as the already mentioned STM studies, have shown the adsorption of anions at metal surfaces and their influence on metal dissolution. Adsorption and complexation by anions may be followed even by XPS if appropriate preparation of the metal surface and its transfer into the UHV is successful. Therefore, detailed studies with modern microscopic and spectroscopic methods are required to obtain detailed insight into the reaction steps of corrosion processes. However, even electrochemical corrosion studies give insight into their mechanism. As an example, the catalysis of iron dissolution according to Heus-ler is presented (Bonhoeffer and Heusler, 1956). 

The complementarity of electrochemical and surface analysis has been described. In principle, both should be accessed regularly in assessing any new corrosion problem in practice, electrochemists and surface scientists are often ignorant of the power of their respective techniques. It is hoped that new microscopic and spectroscopic methods will provide added inducement by their ability to examine the fragile water-filled films that are believed to be so important to pa.ssivation. This could open up a greater dialogue than has been possible in the past. 

As discussed earlier, it is important that corrosion inhibitors are transportable through the resin matrix and therefore this transport was investigated using radiochemical, spectroscopic and conductimetric methods on dry and water immersed resin, different detection techniques being applicable to different inhibitor species. In all cases it was found that diffusion was negligible in dry samples but that diffusing water could "pick up inhibitor species and transport them sufficiently well to compensate for any small amount of depletion of inhibitor at the chip surface. 

The most common type of structure determination is structure verification. In this case, enough information is available (perhaps on the basis of well-known synthetic reaction paths) to propose a probable structure. The structure information which is achieved using IR and Raman spectroscopy is usually sufficient here. One of the fundamental problems in polymer science is the determination of the chemical structure of the repeat unit this moiety determines all of the chemical properties such as reactivity, stability and weatherability. Vibrational spectroscopic techniques are advantageous as a method of determining structure because the methods are applicable to aU polymers regardless of the state of order. The IR and Raman spectroscopy methods are accurate, faster than chemical analysis and reduce exposure to irritating, toxic and corrosive chemicals. 

Li and Ba (2008) prepared silica sol-gel coating of aluminum for corrosion protection using triethoxysilane (TES) as a precursor and characterized the materials using spectroscopic (NMR, FTIR, and Raman) and other methods. Electrochemical data have shown that the sol-gel coating significantly improves the corrosion protection properties of aluminum. The Si NMR spectra of... 

The most commonly used method to measure the concentrations of corrosive gases in field environments is to adsorb the gases on chemicaUy treated filter paper, sometimes followed by a water extraction or chemical treatment, and then to determine the composition and quantity spectroscopically. IBM [75] developed a stacked canister sampler that was adapted for use in the BatteUe studies [79]. Each element in the canister stack collects a specific poUutant. The canisters are easily deployed anywhere in the world, the only inconvenience being that an air pump is required to draw a well-controlled air volume. The reliability of these pumps, based on the author s experience, is less than desirable but adequate. A similar technique, developed largely under the sponsorship of the U.S. EPA, is the "denuder tube. This method is also based on species-specific absorption of pollutants on a chemically treated surface, but in this case a permanent honeycomb substrate is mounted inside a tube. For field sampling, the tubes are stacked, the number depending on the number of species to be analyzed. Airflow pumps are also required in this approach. While this method is more cumbersome than the IBM/Battelle canisters, all the equipment and follow-up chemical analysis can be obtained commercially. 

In the present work the corrosion behavior of AISI types 316L, 316Ti and 321 stainless steels was studied at 750 °C in melts based on a NaCl-KCl equimolar mixture by spectroscopic, gravimetric and electrochemical methods. In addition the surface of the corroded samples was analyzed using metallographic and X-ray microanalysis. Quenched melt samples taken after each experiment were also analyzed chemically to determine the content of the elements of interest. 

This chapter on the fundamentals of corrosion is a short introduction in those parts of thermodynamics and electrochemistry, which are required for an understanding of corrosion phenomena and the related mechanisms. To keep the chapter small enough, only a condensed overview could be given and it should be seen as a recapitulation of the basics. Other important topics for corrosion, especially methods for corrosion research, are not mentioned here. Modern corrosion research applies various in situ and ex situ methods, spectroscopic and surface analytical tools like XPS, AES, Raman and IR-spectroscopy scanning techniques like STM, AFM, SEM, and electron microprobe analysis impedance spectroscopy and potential scanning methods like SRET and SVET and theoretical calculations. The application of these methods will be mentioned in the different chapters. Literature describes these methods in detail, which is recommended to the interested reader [5,. ... 

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