Elucidating the mode of action of a corrosion inhibitor for iron

Two polymetallic iron(III) complexes 1 and 2 have been synthesised from the known corrosion inhibitor 3-(4-methylbenzoyl)-propionic acid HL1 and their crystal structures determined. Coordination geometries extracted from these structures have been used as the basis for molecular modelling onto idealised iron(III) oxide surfaces as an aid to understanding the efficacy of inhibitors of the 4-keto acid type. The proposed mode of action involves 1,3-bridging didentate coordination of the carboxylate function of L1 to two FeIII ions, hydrogen-bond formation between the 4-keto group of L1 and a bridging surface hydroxy group, as well as close packing of the aromatic end groups, which should generate a hydrophobic barrier on the surface. Adsorption isotherm experiments have been used to compare the strengths of binding of related carboxylic acids onto iron(III) oxide surfaces and indicate that the presence of the 4-keto function leads to the formation of significantly more stable surface complexes.     

Adenosine as corrosion inhibitor for mild steel in hydrochloric acid solution

Research on Chemical Intermediates - (2R,3R,4S,5R)-2-(6-amino-9H-purin-9-yl)-5-(hydroxymethyl)oxolane-3,4-diol (adenosine) is an identified component present in agarwood leaf extract. The corrosion...     

Cocos nucifera L. water as green corrosion inhibitor for acid corrosion of aluminium in HCl solution

<正>The ability of Cocos nucifera L.water(CW) as non-toxic corrosion inhibitor for acid corrosion of aluminium in 0.5 mol/L HCl has been studied using chemical technique.CW shows significant inhibition as corrosion inhibitor,with 93%efficiency at the highest concentration of the inhibitor.The inhibitive action is attributed to the adsorption of the inhibitor molecules on metal surface following Langmuir adsorption isotherm.     

Microencapsulation

Microencapsulation is the enveloping of liquid droplets or fine solid particles to form microscopic capsules 1 to 5000 μm in diameter. For the fabrication of such capsules special techniques have been developed which take into account the substance to be encapsulated and the intended use of the capsules. The envelopes, consisting of natural or synthetic polymers, may be made permeable, semipermeable, or impermeable. Thus, there are several possibilities for controlled release of an encapsulated reactive substance, for example by destruction of the envelope or by permeation: alternatively, reactions can be allowed to take place within the microcapsules. Microencapsulation facilitates delivery of many substances to their site of utilization in a novel form of preparation and novel mode of dosage, the solids being dispersed very finely and having a very large surface area.     

Application of AC-SECM in corrosion science: local visualisation of inhibitor films on active metals for corrosion protection

The suitability of frequency-dependent alternating-current scanning electrochemical microscopy (4D AC-SECM) for investigation of thin passivating layers covering the surface of corrosion-inhibited metals has been demonstrated. Inhibition of copper corrosion by benzotriazole (BTAH) and methylbenzotriazole (MBTAH), which are effective inhibitors for this metal under many environmental conditions, was investigated. Strong dependencies were found for the AC z-approach curves with both the duration of the inhibitor treatment and the frequency of the AC excitation signal applied in AC-SECM. Both negative and positive feedback behaviours were observed in the AC approach curves for untreated copper and for Cu/BTAH and Cu/MBTAH samples. Negative feedback behaviour occurred in the low-frequency range, whereas a positive feedback effect was observed at higher frequencies. A threshold frequency related to the passage from negative to positive regimes could be determined in each case. The threshold frequency for inhibitor-modified samples was found always to be significantly higher than for the untreated metal, because the inhibitor film provides electrical insulation for the surface. Moreover, the threshold frequency increased with increasing surface coverage by the inhibitor. 4D AC-SECM was successfully applied to visualizing spatially resolved differences in local electrochemical activity between inhibitor-free and inhibitor-covered areas of the sample.     

Pulse radiolysis study of 2-Mercapto-benzothiazole-a corrosion inhibitor

Pulse radiolysis of 2-Mercaptobenzothiazole (2-MBT) has been undertaken in aqueous solution. The semi-oxidized species formed at pH 4.5 due to the reaction of OH^•, Br₂ ^•− and N₃ ^• and at pH 10.5 with OH^• yielded a spectrum with λ_max = 348 and 595 nm. These semi-oxidized species were able to oxidize phenothiazine drugs (E^o⋟0.8 V). Reducing species such as e_aq ⁻, CO₂ ^•− and H^• atoms react with 2-MBT resulting in the formation of a transient having λ_max = 350 nm and reducing in nature. Kinetic and spectroscopic data of interest are reported.     

Zinc basic benzoate as eco-friendly steel corrosion inhibitor pigment for anticorrosive epoxy-coatings

The inhibitive properties of benzoate anion were known from many years ago but the employment of soluble compounds in anticorrosive paints is limited because their lixiviation would greatly increase coating permeability. However, it is possible to prepare insoluble metallic benzoates with certain cations. This paper describes the experimental procedure to prepare zinc basic benzoate to be employed in anticorrosive paints. The anticorrosive properties of zinc basic benzoate were assessed by electrochemical techniques (corrosion potential and linear polarization measurements). The nature of the compounds forming the protective layer was determined by different techniques, including spectroscopic ones. In a second stage, the anticorrosive properties of the pigment were evaluated by incorporating it in epoxy anticorrosive paints which, in turn, were evaluated by accelerated (salt spray and humidity tests) and electrochemical measurements (electrochemical impedance spectroscopy). The morphology and the nature of the protective layer grown under the paint film in the salt spray chamber was assessed by scanning electron microscopy (SEM) and UV–vis diffuse reflectance spectroscopy.

Experimental results showed that basic zinc benzoate was adequate to formulate epoxy anticorrosive paints with improved anticorrosive performance, especially with the water-borne binder.     

微胶囊化方法

总结了各种制备微胶囊的方法和原理,结合国内外最近几年对微胶囊的研究进展,介绍了一些常用的微胶囊制备方法。     

Water-soluble inhibitor on microbiologically influenced corrosion in diesel pipeline

The effect of water-soluble corrosion inhibitor on the growth of bacteria and its corrosion inhibition efficiency were investigated. Corrosion inhibition efficiency was studied by rotating cage test and flow loop techniques. The nature of biodegradation of corrosion inhibitor was also analyzed by using Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (NMR) and Gas chromatography and mass spectrometer (GC–MS). The bacterial isolates (Serratia marcescens ACE2, Bacillus cereus ACE4) have the capacity to degrade the aromatic and aliphatic hydrocarbon present in the corrosion inhibitor. The degraded products of corrosion inhibitor and bacterial activity determine the electrochemical behaviour of API 5LX steel. The influence of bacterial activity on degradation of corrosion inhibitor and its influence on corrosion of API 5LX have been evaluated by employing weight loss techniques and electrochemical studies. The main finding of this paper is that the water-soluble corrosion inhibitor is consumed by the microbial action, which contributes to the decrease in inhibitor efficiency. The present study also emphasis the importance of evaluation of water-soluble corrosion inhibitor in stagnant model (flow loop test) and discusses the demerits of the water-soluble corrosion inhibitors in petroleum product pipeline.     

Fluconazole as an inhibitor for aluminium corrosion in 0.1 M HCl

The interfacial behavior of fluconazole (FLC) between aluminium and hydrochloric acid has been investigated by using weight loss technique at 30–50 °C. The results showed that fluconazole is an excellent corrosion inhibitor for aluminium in acidic medium. Inhibition efficiency increased with increase in the concentrations of fluconazole but decreased with rise in temperature. The adsorption of the inhibitor on the aluminium surface is found to accord with Temkin adsorption isotherm. Some thermodynamic and activation parameters have been calculated and analysed. The mechanism of physical adsorption is proposed from the values of E_a and obtained. The correlation of inhibition effect and molecular structure of fluconazole was then discussed by quantum chemistry study to further provide insight into the mechanism of the inhibitory action.     

Water-soluble inhibitor on microbiologically influenced corrosion in diesel pipeline

The effect of water-soluble corrosion inhibitor on the growth of bacteria and its corrosion inhibition efficiency were investigated. Corrosion inhibition efficiency was studied by rotating cage test and flow loop techniques. The nature of biodegradation of corrosion inhibitor was also analyzed by using Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (NMR) and Gas chromatography and mass spectrometer (GC–MS). The bacterial isolates (Serratia marcescens ACE2, Bacillus cereus ACE4) have the capacity to degrade the aromatic and aliphatic hydrocarbon present in the corrosion inhibitor. The degraded products of corrosion inhibitor and bacterial activity determine the electrochemical behaviour of API 5LX steel. The influence of bacterial activity on degradation of corrosion inhibitor and its influence on corrosion of API 5LX have been evaluated by employing weight loss techniques and electrochemical studies. The main finding of this paper is that the water-soluble corrosion inhibitor is consumed by the microbial action, which contributes to the decrease in inhibitor efficiency. The present study also emphasis the importance of evaluation of water-soluble corrosion inhibitor in stagnant model (flow loop test) and discusses the demerits of the water-soluble corrosion inhibitors in petroleum product pipeline.     

Ceforanide: a new and efficient corrosion inhibitor for mild steel in HCl solution

The corrosion inhibition properties of ceforanide for mild steel in HCl solution were analyzed by electrochemical impedance spectroscopy, potentiodynamic polarization, and gravimetric methods. The increase in inhibitor concentration and immersion time showed a positive effect on inhibition efficiency. The experimental data showed a frequency distribution and therefore a modeling element with frequency dispersion behavior and a constant phase element have been used. In aqueous acid solution, mild steel reacts by evolution of hydrogen. Visual observations showed that the hydrogen evolution decreased (i.e., corrosion inhibition effect increased) with increasing concentration of ceforanide. Potentiodynamic polarization study revealed that ceforanide acted as a mixed type of inhibitor. The results obtained from different methods are in good agreement. The adsorption behavior of ceforanide is experimentally investigated by contact angle measurement on metal surface. The contact angle of metal surface to the acid solution increased with inhibitor concentration; thereby confirming the increased hydrophobic nature of metal surface to the acid solution having inhibitors.     

Encapsulation of the corrosion inhibitor 8-hydroxyquinoline into ceria nanocontainers

Ceria nanocontainers were synthesized through a two-step process and then loaded with 8-hydroxyquinoline (8-HQ). The size of the containers was 110 nm as determined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). X-ray diffraction analysis (XRD) showed that the ceria nanocontainers were of the cerianite crystalline phase. The presence of 8-HQ in the nanocontainers was confirmed with Fourier-transform infrared spectroscopy (FT-IR). The loading of the inhibitor in the nanocontainers was estimated with differential thermal analysis (DTA) and thermogravimetric analysis (TGA). The loading amount of 8-HQ was 4.28% w/w. Based on the size of the nanocontainers and the assumption that they are not broken, we deduced that there were approximately 6.0 × 10⁵ molecules of 8-HQ per container. Furthermore, release of 8-HQ in a corrosive environment was studied by potentiodynamic measurements, showing that the inhibitor is released from the nanocontainers, suppressing the corrosion activities by a strong barrier effect. SEM and dynamic light scattering (DLS) measurements confirmed that the nanocontainers are not significantly agglomerated and maintain their shape after suspension in 0.5 M NaCl solution for more than 72 h.     

Release mechanism of electrodeposited polypyrrole doped with corrosion inhibitor anions

Scanning Kelvin probe and electrochemical impedance spectroscopy were used to study the release behaviour of inhibitor anions doped in polypyrrole film (e.g. molybdate, 3-nitro salicylate). The polypyrrole coatings were formed on mild steel and zinc substrates in aqueous solution. It was shown that the release behaviour of the molybdate and 3-nitro salicylate anions depends on the size of cations in the electrolyte. The delamination is determined with the migration and incorporation of small cations.     

Surface analysis methods in the investigation of corrosion inhibitor performance

Summary Being economical and easily applied, organic corrosion inhibitors are finding increasing use. The efficacy of inhibitors is normally investigated by gravimetric and electrochemical methods. For further information — for example, on the thickness, composition and structure of protective films, or the binding states of the inhibitor and metal — surface analysis methods, such as ESCA, AES, SIMS and LAMMA, must be used. The system copper/ benzotriazole or tolyltriazole in tap water is investigated as an example of interface inhibition. A quasipolymeric film with a thickness of only a few molecular layers is formed from Cu(I) and inhibitor and is remarkably resistant even to air and solvents. Phosphonic acids act as membrane inhibitors on iron in cooling water. Together with corrosion products and ions from the water they form layers with a thickness of about 20–40 nm. As their growth then ceases, they cause no hindrance to heat transfer.

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Oberflächenanalytische Methoden zur Untersuchung der Wirksamkeit von Korrosionsinhibitoren

     

Surface analysis of corrosion inhibitor films by XPS and ToFSIMS

In recent years developments in the capabilities of techniques such as XPS and static SIMS have led to wider application of these methods for the characterisation of industrial materials. After a brief discussion of recent key developments of these techniques, this paper presents a selection of results from research work at our laboratory in the characterisation of organic film-forming corrosion inhibitors on a range of metal substrates which illustrate the nature of the information available. The inherent advantage ofsurface sensitivity and the advantages of a multi-technique approach for the evaluation of surface molecular structure from complex organic compounds is discussed. The additional benefits for analysis offered by the latest developments in technique are also demonstrated.     

Perezone as corrosion inhibitor for AISI 1018 steel immersed in NaCl saturated with CO2

Journal of Solid State Electrochemistry - An electrochemical study of natural compound perezone as a corrosion inhibitor of 1018 steel immersed in 3% NaCl solution saturated with CO2 was conducted...     

Xanthione: A new and effective corrosion inhibitor for mild steel in sulphuric acid solution

The adsorption and inhibition effect of xanthione (XION) on mild steel in 0.5 M H₂SO₄ at 303–333 K were studied using gravimetric and UV–visible spectrophotometric methods. The results obtained show that XION acts as an effective corrosion inhibitor for mild steel in sulphuric acid and inhibition efficiency reaches 98.0% at a very low inhibitor concentration of 10 μM. Inhibition efficiency was found to increase with increase in XION concentration but decreased with temperature suggesting physical adsorption mechanism. Arrhenius law and its transition equation lead to estimate the activation parameters of the corrosion process. XION inhibits the corrosion of mild steel effectively at moderate temperature and adsorbs according to the Langmuir isotherm. Thermodynamic parameters governing the adsorption process have been calculated and discussed. The UV–visible absorption spectra of the solution containing the inhibitor after the immersion of mild steel specimen indicate the formation of a XEN–Fe complex. Attempt to correlate the molecular structure to quantum chemical indices was made using density functional theory (DFT).