Corrosion inhibitors spectroscopy

UV spectroscopy can be used to detect low levels of organic corrosion inhibitors in produced water. An analytic method has been developed using a diode array UV spectrophotometer [630]. 

There have been some examples of the use of LDMS applied to the analysis of compounds separated via TLC, although not specifically dealing with polymer additives [852]. Dewey and Finney [838] have described direct TLC-spectroscopy and TLC-LMMS as applied to the analysis of lubricating oil additives (phenolic and amine antioxidants, detergents, dispersants, viscosity index improvers, corrosion inhibitors and metal deactivators). Also a series of general organics and ionic surfactants were analysed by means of direct normal-phase HPTLC-LMMS [837]. Novak and Hercules [858] have... 

X-Ray photoelectron spectroscopy (XPS) was used to examine the surface of steel that had been exposed to 1.0 M hydrochloric acid in the presence of 3,5-diphenyF4//-l,2,4-triazole 27 as corrosion inhibitor. These measurements demonstrated that the inhibitor 27 was chemisorbed on to the metal surface the protection afforded by 27 was still... 

Fourier transform infrared reflection-absorption spectroscopy (FT-IFRAS) is applied to the study of corrosion protection of copper by an organic coating. Poly-N-vinyliroidazole (PVI(D) and poly-4(5)-vinylimidazole (PVI(4)) are demonstrated to be effective new polymeric anti-corrosion agents for copper at elevated temperatures. Oxidation of copper is suppressed even at 400° C. PVI(1) and PVI(4) are more effective anti-oxidants than the most commonly used corrosion inhibitors, benzotriazole and undecyllmldazole, at elevated temperatures. These new polymeric agents are water soluble and easy to treat the metal surface. 

Alkoxybenzotriazoles are effective corrosion inhibitors of copper and copper alloy <90EUP397455). The anticorrosion of benzotriazole on copper has been studied by surface-enhanced Raman spectroscopy, elUpsometry, and electrochemical techniques <86MI 401-01). 

Chadwick D, Hashemi T. Adsorbed corrosion inhibitors studied by electron spectroscopy Benzotriazole on copper and copper alloys. Corrosion Sci 1978 18 359. 

S.6.4.7.2 Corrosion Inhibitors The corrosion process and the mechanism of inhibitors is an important research direction for electrochemistry. Raman spectroscopy is advantageous in the investigation of adsorption-mediated corrosion inhibition, because it is readily applicable to the in situ observation of the behavior of inhibitors... 

Peptides are known to show some specificity toward metal binding, as was shown by titration experiments nsing H-NMR [7,8], potentiometry [9], luminescence measnrements [10], infrared (IR), circular dichroism (CD), and ultraviolet (UV spectroscopies [11]. Poly-L-aspartic acid binds to metals such as Eu, Ce, La +, Cu ", and Pb ", and acts as a corrosion inhibitor for steel and iron. This property has been ascribed to the carboxylate side chain of aspartic acid [12,13]. 

Investigation of electrode solution interfaces by in situ vibrational spectroscopy has two principal advantages firstly the species present and their structures are directly characterized by their spectra and, secondly, these spectra are sensitive to the environment and therefore can be used to probe complex interactions. Raman spectroscopy is particularly well suited to the investigation of aqueous systems and in certain cases the adsorption of neutral species, of anions in the double layer and of the solvent (as well as interactions between these species) can now be characterized[48]. Vibrational spectroscopy of systems of practical importance is illustrated by the Surface Enhanced Raman Spectra (SERS) of the corrosion inhibitor thiourea adsorbed at silver and copper electrodes[49] it should be noted that inhibitors such as thiourea are also used as plating additives. 

The buildup of soluble corrosion products can be used to monitor corrosion kinetics. This method has been used extensively in oil field corrosion inhibitor testing, particularly in sweet (CO2) systems with only small amounts of HjS present [29]. Iron analysis in the laboratory is most rapidly done on the bench with the Hach method (Phenantridine) [.30], although a host of other wet chemical methods are applicable. Instrumental methods include Atomic Absorption Spectroscopy (AAS) and Inductively Coupled Argon Plasma Spectroscopy (ICAP). While both these methods are well suited for high volume routine analysis, care must be taken that the samples are not contaminated by even traces of hydrocarbons. This includes soluble hydrocarbons such as methanol, chelating compounds such as EDTA, or scale inhibition products. Also used in the laboratory is Ion Chromatography (IC). This latter method is even more sensitive to sample composition and not recommended on a routine basis. 

Resonance Raman spectroscopy has been used as a tool to investigate the mode of corrosion protection by films of PANI on iron [466]. Spectra as displayed in Figure 47 in connection with measurements of the iron electrode potential implied that the emeraldine salt found at positive electrode potentials acts as a corrosion inhibitor of iron in its passive state, whereas the reduced leucoemeraldine salt is indicative of an iron surface at its corrosion potential. 

Shabanova 1. N., Chausov F. R, Naimushina E. A., Kazantseva 1. S. AppUcation of the X-ray photoelectron spectroscopy method for investigating the molecular structure of the corrosion inhibitor complex of 1-hydroxietylidene diphosphonic acid with zinc Zhumal struktumoi khimii. 2011. Vol. 52. Supplement. C. S113-S118. 

The structure of a mild steel oxide layer built up under different environmental conditions and, in particular, its interaction with corrosion inhibitors is not yet completely clarified (Seo and Sato, 1989 Ryan, 1995 Graham, 1995). The surface analytical techniques of X-ray photoelectron spectroscopy (XPS) and X-ray excited Auger-electron spectroscopy (XAES) are very useful for identifying the different chemical states... 

Successful inhibitor tests require suitable corrosion measurement and analysis techniques that are able to correctly record and interpret corrosion rate data. Many testing and monitoring techniques that were developed initially for the diagnosis and prediction of corrosion have been successful employed in laboratory and field corrosion inhibitor testing and research. These techniques include the use of corrosion coupons, solution analysis, electrical resistance probe, polarization resistance, electrochemical impedance spectroscopy and many other physical, electrical and electrochemical methods. 

Recent developments in the mechanisms of corrosion inhibition have been discussed in reviews dealing with acid solutions " and neutral solu-tions - . Novel and improved experimental techniques, e.g. surface enhanced Raman spectroscopy , infrared spectroscopy. Auger electron spectroscopyX-ray photoelectron spectroscopyand a.c. impedance analysis have been used to study the adsorption, interaction and reaction of inhibitors at metal surfaces. 

The impedance spectroscopy of steel corrosion in concentrated HC1, with and without inhibitors, exhibit relatively straightforward electrochemical phenomenology and can be represented by simple equivalent circuits involving primarily passive electrical elements. Analysis of these circuits for steel corroding in HC1 per se reveals that the heterogeneity of the surface is established rapidly and can be simulated with a simple electrical circuit model. 

Kendig, M. et al. "The application of impedance spectroscopy to the evaluation of corrosion protection by inhibitors and polymer coatings", CORROSION 85. 1985, NACE, Houston, Texas, Paper 74. 

During recent years, SERS spectra have been used to acquire basic information on new inhibitors [74-77], and also on the adsorption mode of benzotriazole in new solvent environments such as ionic liquids [78]. Thus, three decades after the pioneering studies [19-21], SERS spectroscopy is becoming a standard technique in studies of Cu corrosion inhibition. 

All derivatives of the benzo-hydroxamic acid inhibited copper corrosion more effectively than BHA itself. The efficiency was affected much more by hydrophobic bulkiness in the phenyl ring than by the electronpushing or electron-attracting character of the substituents. The results attained by electrode impedance spectroscopy and quartz crystal nanobalance techniques led to recognition that the higher efficacy was not due to the inductive effect of the substituents, as both chloro and methyl substitution led to enhanced inhibition. The most important factor is the hydrophobic bulkiness. In the inhibition process, the inhibitor molecule is attached to the copper surface by the polar group (CON"), and the apolar hydro-phobic moiety may block the metal surface... 

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