Correlation of the Structure and the Inhibitive Action of Some Sulphoxides

Abstract

Three aliphatic and three aromatic sulphoxides (dimethyl di-n-butyl, tetramethylene, dibenzyl, diphenyl, and di-p-tolyl sulphoxide) have been tested for their ability to inhibit the corrosion of iron in a 1 N solution of H₂SO₄, and their anti-corrosive activity has been correlated with their chemical constituiion. The anodic and cathodic polarisation curves and the corrosion rates are explained by assuming that sulphides formed by the reduction of the sulphoxides. inhibit corrosion. The anti-corrosive activity of these sulphoxides is influenced by the electron density on the sulphur atom and their rate of reduction to sulphide.     

Inhibitoren der Korrosion 23 (1) – Gibt es eine Struktur- Wirkungs-Beziehung bei organischen Inhibitoren der Korrosion von Aluminium?

Corrosion inhibitors 23 (1) – Does there exist a structure-efficiency relation in the organic inhibitors of aluminium corrosion? Over 400 organic compounds have been routinely tested as potential inhibitors for the corrosion and dissolution of aluminium in In HCl/2,5% NaCl solution, using 10^?2 m/l as the concentration of the organic compound being tested. It was attempted to derive a relationship between efficiency of the inhibitor with molecular structure. Particular attention was devoted to the following classes of compound: organoarsenic; phosphonic and phosphinic acids; aromatic aldehydes and ketones; aromatic and aliphatic carboxylic acids; dihydric phenols; tetrazolium salts and formazan compounds; sulphoxides and aromatic sulphonic acids; sulphonamides and sulphones. For a selected number if inhibitors, the dependence of concentration and the effect of an oxygen-containing atmosphere were studied. Compounds which show good inhibition in the corrosion of aluminium are consistently even better in the protection of zinc surfaces. The mechanism of the corrosion inhibition is not clear, but the results suggest that the total molecular structure of the inhibitor must be considered, with particular importance paid to the nature and the spatial relationship of the different functional groups.     

Corrosion Protection of Phenolic-Epoxy/Tetraglycidyl Metaxylediamine Composite Coatings in a Temperature-Controlled Borax Environment

The failure behavior for two kinds of phenolic-epoxy/tetraglycidyl metaxylediamine composite coatings in 60 °C borax aqueous solution was evaluated using electrochemical methods (EIS) combined with scanning electron microscopy, confocal laser scanning microscope, water immersion test, and Raman spectrum. The main focus was on the effect of curing agent on the corrosion protection of coatings. Results revealed that the coating cured by phenolic modified aromatic amine possessed more compact cross-linked structure, better wet adhesion, lower water absorption (0.064 mg h^?1 cm^?2) and its impedance values was closed to 10⁸ Ω cm² after immersion for 576 h, while the coating cured by modified aromatic ring aliphatic amine was lower than 10⁵ Ω cm². The corrosion mechanism of the two coatings is discussed.     

Corrosion Inhibitors for Aluminium Alloys

Data (including literature data) are presented on the inhibition of the corrosion of Al and some Al alloys in hydrochloride, sulfuric, acetic and oxalic acids and sodium hydroxides. In this context the influence is shown of parameters such as inhibitors structure and concentration, temperature, time, medium concentration and external currents. Inhibitors dealt with include aliphatic and aromatic amines, carbonyl compounds (aldehydes, ketones); in this context it is shown that functional groups and their relative positions may have an important effect on inhibitor efficiencies.     

Biodegradation and corrosion behavior of manganese oxidizer Bacillus cereus ACE4 in diesel transporting pipeline

The degradation problem of petroleum products arises since hydrocarbon acts as an excellent food source for a wide variety of microorganisms. Microbial activity leads to unacceptable level of turbidity, corrosion of pipeline and souring of stored product. The present study emphasizes the role of Bacillus cereus ACE4 on degradation of diesel and its influence on corrosion of API 5LX steel. A demonstrating bacterial strain ACE4 was isolated from corrosion products and 16S rRNA gene sequence analysis showed that it has more than 99% similarity with B. cereus. The biodegradation and corrosion studies revealed that B. cereus degraded the aliphatic protons and aromatic protons in diesel and is capable of oxidizing ferrous/manganese into oxides. This is the first report that discloses the involvement of manganese oxidizer B. cereus ACE4 on biodegradation of diesel and its influence on corrosion in a tropical country pipeline.     

Studies of the effect of some fatty acids on the inhibiting properties of nitrated petroleum products

The variation in inhibitive effectiveness of some aliphatic acids in the oil coating on steel has been established on the basis of corrosion and electrochemical studies in distilled water and K₂SO₄ solution. This differentiated effectiveness is ascribed to different spatial orientation of molecules of the investigated saturated and unsaturated acids. The observed increase of protective effectiveness of a saturated hydroxy-acid is explained by additional tightening of the layers formed on iron surface as a result of hydrogen bonds. The synergism of inhibitors, a nitrated petroleum product (US), and some saturated fatty acids in an oil coating on steel is ascribed to the double task performed by the acids: as a rapidly acting component of the mixture during the first step of the corrosion process and as an inhibitor shielding and stabilizing the first chemisorbed layer formed by the US inhibitor on the surface of iron during the second step of the corrosion process.     

Inhibition of corrosion of aluminium-51S in hydrochloric acid solutions

The paper describes the performance of aliphatic polyamines and ethanolamine as corrosion inhibitors for Al-51S in hydrochloric acid solutions. These inhibitors function mainly by adsorption and their neutralizing effect has a secondary role in inhibition. Activation energies in the presence and absence of inhibitors have been given. The performance of inhibitors under the influence of external cathodic polarization has been evaluated. The protective potential is not a constant value and varies with each system, and changes with inhibitor concentration. It seems that an increase in ethylenediamine units in the linear chain does not favour inhibitive action. All inhibitors are predominantly cathodic in action.     

Korrelationsbetrachtungen zum Einfluß von Säureinhibitoren auf die Metallauflösungsgeschwindigkeit und die Kinetik der Wasserstoffabsorption

Considerations on the correlations between inhibition of metal dissolution and hydrogen absorption in the use of acid inhibitors Evaluating literature data on the impact of 53 quarternary ammonium salts, 13 aliphatic and aromatic aldehydes and 12 aliphatic and aromatic ketones on the inhibition of the rate of metal dissolution and the hydrogen permeation currents at steel in H₂S-free and H₂S-saturated 16% hydrochloric acid at ambient temperature, it is demonstrated by rank correlation considerations that there is no correlation between activity in blocking the metal dissolution rate and efficiency in decreasing the hydrogen absorption rate of the metal. Furthermore, there is no correlation between antipromotor/promotor-efficiency at the free corrosion potential and at cathodic polarization in H₂S-free and H₂S-saturated acid. Problems of H-absorption therefore have to be investigated for any particular case under conditions as close to the practice as possible.     

The use of quantum mechanics calculations for the study of corrosion inhibitors

In order to study the ability of quantum chemistry to select corrosion inhibitors, quantum mechanics calculations have been applied to different linear chain diols, diamines and aliphatic aminoalcohols. The corresponding structures have been optimized, and the energies and coefficients of their molecular orbitals have been calculated, using the semi-empirical method MINDO/3. Finally, the theoretical results obtained have been compared with the experimental data.     

Corrosion behavior of composite brake materials

It is very important to study the corrosion behavior of composite brake materials for their design, manufacture, and application. In the study, one kind of composite brake material used in engineering machinery, two kinds used in automobiles, and gray cast iron HT200 were selected as tested materials. Their corrosion behavior in typical acid solution, alkali solution, salt solution, running water, and air were investigated. The results showed that some components of composite brake materials, such as iron matrix, steel fiber, and iron powder, were easily subject to corrosion in acid solution. Corrosive pitting, net‐like cracking, and breakage appeared at their corrosion surfaces, and in the solution of 3.5% NaCl, corrosive pitting took place and corrosion holes of 2–8 µm diameter formed at the corrosion surface of these components. But when brake materials were exposed to the solution of 5% NaOH, the organic binder was corroded seriously, nearly parallel cracks formed at the corrosion surface and some samples even became loose powders because the corrosion makes the binder lose its adhering function. In running water and air, the tested samples have an excellent corrosion resistance, and the composite brake material containing organic binder has a better corrosion resistance compared with other tested materials. The investigation has also indicated that the interface between ingredients easily corrodes.     

Structural factors determining the inhibitive effect of alkyl(aryl)ammonium salts of functionalized perfluoropolyethers

Thirty homologous series of functionalized perfluoropolyethers (FP) based on alkyl(aryl)ammonium salts were studied, by correlation analysis and statistical data processing, as inhibiting constituents of perfluoropolyether lubricating greases. The basic adsorption and colloid-chemical factors responsible for the inhibitive effect of FPs are the high critical micell concentration, surface activity, hydrophobicity, and formation of chemoadsorption complexes, in which FPs function as electron-donating agents. Contributions from ten basic structural factors of FPs (carboxylate and arylsulfonate anions, electronic structure of an anchor heteroatom, active hydrogen atoms of NH- and OH-acids in aliphatic and aromatic fragments, aliphatic radicals, aromatic fragment in an alkylammonium cation, etc.), influencing their inhibitive effect in low-polarity media, were quantitatively estimated.     

The effect of the nature of binary water–organic solvents on thermodynamic characteristics of adsorption of aromatic compounds on hyper-cross-linked polystyrene

Using high-performance liquid chromatography under conditions close to equilibrium, adsorption has been investigated for a series of aromatic compounds from water–acetonitrile, water–methanol, and water–isopropyl alcohol solutions on hyper-cross-linked polystyrene with the degree of cross linking of 500%. The principles of the effect of the nature of binary water–organic solvents on thermodynamic characteristics of adsorption of the studied substances on hyper-cross-linked polystyrene have been determined. The role of intermolecular interactions, which are realized in bulk solution and interface, in the adsorption of aromatic compounds from their maximum diluted water–organic solutions on hyper-cross-linked polystyrene has been discussed. The compensation effect upon adsorption on hyper-cross-linked polystyrene individually from water–acetonitrile solution and various water–alcohol solutions has been discovered. The existence of linear dependences between the differences of Gibbs energy upon adsorption from water–organic solutions on hyper-cross-linked polystyrene has been shown.     

The effect of temperature on the galvanic corrosion of the copper/AISI 304 pair in LiBr solutions under hydrodynamic conditions

The corrosion behaviour of copper and AISI 304 stainless steel and the galvanic corrosion generated by the copper/AISI 304 pair, have been studied by electrochemical methods. These materials have been tested in an 850 g/L LiBr solution at different temperatures (25-75 °C) and at different Reynolds numbers (1456-5066) in order to study their performance in absorption machines. Results show that copper was always the anodic element of the pair and its corrosion resistance decreases due to the AISI 304 stainless steel galvanic effect. Galvanic corrosion increases with temperature and Reynolds number. However, it was proved that the effect of temperature on galvanic corrosion is more influential than the Reynolds number effect. This fact is also certain for corrosion of uncoupled copper and for corrosion of AISI 304 stainless steel. Experimental values of the corrosion current densities fit well the Arrhenius plot at all the Reynolds numbers analysed and a potential relation between the corrosion current densities and the Reynolds number has been found.     

Synergistic influence of iodide ions on the inhibition of corrosion of C-steel in sulphuric acid by some aliphatic amines

The synergistic influence caused by iodide ions on the inhibition of corrosion of C-steel in 1 M H₂SO₄ in the presence of some aliphatic amines has been studied using weight loss, potentiodynamic polarization, linear polarization and a.c. impedance techniques. Aliphatic amines used inhibit the corrosion of C-steel and the inhibition efficiency increases by increasing the concentration of the additives and also by addition of iodide ions. The adsorption of these compounds is found to obey Frumkin’s adsorption isotherm. The increase in surface coverage in the presence of iodide ions indicates that iodide ions enhance the adsorption of these aliphatic amines on the metal surface. Defines and evaluates synergism parameter (S_θ). Values of the parameter which are more than unity indicate the fact that the enhanced inhibition efficiency in the presence of iodide ions is only due to synergism and there is a definite contribution from the inhibitors molecules, which are adsorbed by coulombic interaction on the metal surface, where iodide ions are already adsorbed and thus reduces the corrosion rate.     

The inhibitive action of some azoles towards the corrosion and dezincification of 70Cu---30Zn brass in ammonia solution

An attempt has been made to study the effect of some azoles on the corrosion and dezincification of 70Cu---30Zn brass in ammoniacal solution using weight loss, solution analysis and potentiostatic polarization techniques. The inhibition efficiency of azoles for the corrosion and the dezincification of 70Cu---30Zn brass has been found to decrease in the order benzimidazole > 2-mercaptobenzothiazole > benzotriazole. Benzimidazole has been found to give almost complete protection against corrosion as well as dezincification of 70Cu---30Zn brass in ammoniacal solution. Potentiostatic polarization studies have shown that all the compounds inhibit both cathodic as well as anodic reactions, indicating a mixed type of inhibition.     

电弧喷涂Al-Zn-Si-RE合金涂层与Al-Zn伪合金涂层的耐蚀性能对比

为研究Al-Zn-Si-RE合金涂层和相同Al含量的Al-Zn伪合金涂层耐蚀性能的不同,采用电弧喷涂技术在Q235钢表面制备了此两种合金涂层。通过盐水全浸实验和电化学测试技术对比研究了两种涂层的耐腐蚀性能,并将两种涂层的极化曲线与纯Zn、纯Al、Zn-15Al合金涂层进行了对比分析。使用扫描电镜、金相显微镜和X-射线衍射仪等手段测试分析了两种合金涂层腐蚀前后的微观组织形貌和相组成。结果表明,Al-Zn-Si-RE合金涂层的自腐蚀电位和自腐蚀电流密度分别为-0.995V和3.319×10-6 A/cm2,腐蚀电位更正,腐蚀电流密度更低,耐蚀性更好,原因可能是致密的腐蚀产物膜抑制了腐蚀作用;Al-Zn-Si-RE合金涂层与伪合金涂层微观组织成分和相结构的不同引起腐蚀行为的差异,且Al-Zn-Si-RE合金涂层表现出更好的耐盐水腐蚀性能;稀土元素的存在有利于提高Al-Zn-Si-RE合金涂层的耐蚀性。     

Identification of steel corrosion associated with sulfate-reducing bacteria by electrochemical noise technique

Deterioration of steel structures in natural waters can result from microbiologically influenced corrosion (MIC) such as that caused by sulfate-reducing bacteria (SRB). Corrosion pits associated with MIC have been recently observed in submerged steel bridge piles and there is renewed interest to assess their deterioration. Conventional electrochemical techniques to identify MIC have been complicated due to the effects of the surface films and the mechanism for charge transfer by the bacteria on the steel surface. An electrochemical noise (EN) technique to identify steel corrosion in an aqueous solution has been developed and the method ideally can identify the onset of local pitting, but complications and limitations relating to data acquisition, filtering, and interpretation exist. EN analysis was shown to differentiate SRB and corrosion activity including initial biofilm development, pitting corrosion development, and diminution of SRB activity. Electrochemical behavior, environmental characteristics, SRB activity, and corrosion modality provided consistent correlation to EN and localized corrosion development.     

Corrosion and stress corrosion cracking of amorphous FeNiMoxB alloys in several neutral and acidic media

Corrosion and stress corrosion cracking behaviour of a series of amorphous iron alloys FeNiMo_xB (x = 0, 2, 4, 8.5) has been investigated in several neutral and acidic media. In particular in aqueous solutions of ferric chloride, potassium tetrathionate and sulphuric acid containing chlorides stress corrosion cracking (SCC) has been studied by means of constant strain tests and corrosion rates have been evaluated by means of weight loss measurements. In several cases polarization curves have been recorded in order to clarify the electrochemical behaviour of the amorphous alloys. SEM observations of the fracture surfaces have been performed. It has been observed that the glassy alloys under investigation are susceptible to SCC at free corrosion potential in all the environments. SCC has been observed on specimens cathodically and anodically polarized in sulphuric acid containing chlorides. Hydrogen embrittlement can reasonably be considered responsible of the SCC phenomenon, except in sulphuric acid solution on specimens anodically polarized and in iron chloride solution. A deleterious effect of molybdenum has been noted on the corrosion rates of unstressed specimens and on the time to failures of stressed samples.     

Reactivity of polyester aliphatic amine surfactants as corrosion inhibitors for carbon steel in formation water (deep well water)

Effect of different concentrations, 40-200 ppm, of various polyester aliphatic amine surfactants on inhibition of the corrosion of carbon steel in the formation water (deep well water) was investigated. These surfactants exhibit different levels of inhibition particularly at high concentration (200 ppm). Inhibition efficiencies in the range 86-96% were determined by weight loss method. Comparable results were obtained from electrochemical measurements using Tafel extrapolation and polarisation resistance methods. It was shown that all the investigated surfactants act primarily as anodic inhibitors; however, they also affect the rate and mechanism of the cathodic reaction. These compounds function via adsorption on reactive sites on the corroding surface reducing the corrosion rate of the metal. It was revealed that the adsorption of these surfactants obey Langmuir adsorption isotherm. The inhibition effectiveness increases with the length of the aliphatic hydrocarbon chain, being a maximum in the presence of surfactant IV (∼96% efficiency). The corrosion inhibition feature of this compound is attributed to the presence of a long hydrocarbon chain that ensures large surface coverage as well as the presence of multiple active centers for adsorption. Scanning electron microscopy, SEM, has been applied to identify the surface morphology of carbon steel alloy in the absence and presence of the inhibitor molecules.     

Mg–Zr alloy behavior in basic solutions and immobilization in Portland cement and Na-geopolymer with sodium fluoride inhibitor

The dismantling of uranium natural graphite gas nuclear reactor generates a large volume of fuel cladding. The fuel cladding materials are based on Mg–Zr alloy for UNGG. The dismantling strategy could be to encapsulate these wastes into an ordinary Portland cement (OPC) or Na-geopolymer (alumino-silicate material) in a form suitable for storage. Corrosion behavior of Mg–Zr in OPC interstitial solution and activating solution of Na-geopolymer has been studied in the presence and absence of sodium fluoride as corrosion inhibitor. Electrochemical methods have been used to determine the corrosion densities. Results show that the corrosion densities of Mg–Zr alloy in OPC solution are one order of magnitude more important than in activating solution of Na-geopolymer and sodium fluoride addition decreases corrosion densities in OPC interstitial solution. Hydrogen evolution of encapsulated Mg–Zr alloy has also been measured in both OPC and Na-geopolymer and results show that Na-geopolymer matrix appears to be an attractive binder in term of corrosion performance.