A review of studies on migrating corrosion inhibitors (MCI) for the protection of steel reinforcement in concrete when exposed to chlorides is presented. Four MCI groups are considered: (1) Inorganic MCI; (2) Organic MCI, including electromigration corrosion inhibitors (EMCI); (3) Mixed MCI (a mixture of inorganic and organic MCI); (4) Organic MCI with hydrophobic components. Inorganic MCI were among the first to be studied. They are not widely used due to their low penetrating power, interaction with cement stone and possible negative impact on the environment. Organic MCI are well studied and commercially available, especially MCI based on amines and amino alcohols. In most cases, such mics effectively reduce the rate of corrosion both for new concretes that were not exposed to chlorides before treatment with an inhibitor, and for structures containing chlorides. Isolated studies have also reported their low effectiveness. Mixtures of organic and inorganic components in MCI often have a synergistic effect, which increases the anticorrosive effect. Modification of organic MCI with hydrophobic components enhances efficiency due to the additional effect on the concrete coating. In general, the use of MCI represents a promising and developing approach to prolonging the service life of reinforced concrete structures exposed to chlorides.
Cupressus is one of several genera of evergreen conifers within the family Cupressaceae that have the common name cypress. The efficiency of Cupressus macrocarpa extract (CME) as corrosion inhibitor for Al in 1 M HCl medium was carried out using weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation techniques. The results prove that the chemical content of CME can inhibit the corrosion rate of Al and exhibit high inhibition efficiency. Also, the results showed variation in inhibition performance of the extract with varying concentrations, immersion time and temperature. Temkin was tested to describe the adsorption behavior of the extract on the Al surface. Potentiodynamic polarization study clearly revealed that extract acts as a mixed type of inhibitor. According to the EIS study’s findings, the charge transfer resistance (Rct) increased while the double layer capacitance (Cdl) decreased. The extract is adsorbed on the Al surface, covering larger area from the surface of Al and hence, %IE increases. The adsorption of the extract on the Al surface is spontaneous, according to kinetic and thermodynamic characteristics and stable. CME inhibits corrosion on the Al surface through physical and chemical adsorption. According to the findings, CME may be useful as a corrosion inhibitor for Al in 1 M HCl.
The results of four one-year exposions of typical metals at three Vietnam corrosion test stations in rural, urban and marine atmospheres are obtained. At each corrosion test station, the samples were installed in two directions: in a non-marine atmosphere to the south and to the north, in a marine atmosphere to the sea and from the sea. The beginning of each exposure corresponded to the beginning of the season of the year. The difference in one-year corrosion losses of metals depending on the orientation of the samples and the beginning of exposure is shown. For each corrosion test station, the atmospheric corrosivity categories are determined in relation to each metal. It is shown that atmospheric corrosivity in each place is not definitely in relation to all metals.
The effect of sodium benzoate (BS) additives on known copper corrosion inhibitors 1,2,3-benzotriazole (BTA) and sodium laurate (LS) in neutral chloride solutions is considered. It has been shown that the addition of BTA to these compounds increases the protective properties of BTA and LS on the MNZh-5-1 copper alloy. According to polarization measurements, there is a sharp shift in the potential of local depassivation in the case of combined use of BTA with BS at their equimolar ratio. According to the results of corrosion tests, both studied equimolar compositions with BS protect the copper alloy from corrosion in a 3% NaCl solution.
Electrochemical impedance spectroscopy is a method for studying various properties of coatings, including conversion coatings on aluminum alloys. This method allows to analyze corrosion processes and protection mechanisms, providing information about the structure and properties of coatings. Chromate-free coating technologies by chemical oxidation continue to evolve, so understanding what characteristics coatings on various aluminum alloys will have, depending on the composition of the converting solution and modifying additives, is an urgent task. In this article, inhibited and non-inhibited chromate-free conversion coatings of IFKHANAL-3 modified with 1,2,3-benzotriazole and tolyltriazole (5-methylbenzotriazole) were studied using the electrochemical impedance method. It has been shown that modifying additives have different effects on coatings on D16 and V95T3 alloys, which is probably due to the different content of alloying elements and, first of all, the amount of copper in the alloys. In this case, the subsequent filling of coatings in a corrosion inhibitor solution shows the greatest effect for modified coatings if the initial coating had greater uniformity, according to the calculated impedance parameters.
Diffusion studies of the penetration of phosphoric acid, dimethyl sulfoxide, and methyl ethyl ketone solutions into modified amine-cured epoxides have been carried out. A zone of polymer fluorescence change has been detected under the influence of internal stresses arising from swelling in phosphoric acid. It is shown that under various spectral conditions for observing the fluorescence of epoxy binders and adaptive composites when exposed to phosphoric acid or dimethyl sulfoxide, it is possible to digitalize MPIs for subsequent multifractal analysis.
The article presents data on the redox properties of solutions of mineral acids (H2SO4, HCl, H3PO4) and their mixtures (H2SO4+H3PO4, HCl+H3PO4) containing Fe(III) and Fe(II) cations with a total concentration of 0.1 M. For these systems, the values of the electrode potentials of the Fe(III)/Fe(II) redox couple were measured in the temperature range of 20−95°C using potentiometry on a platinum electrode. The redox potentials of systems in the solutions in question are poorly described by the Nernst equation. The observed deviations result from the non-equivalent complexation of potential-determining species, namely Fe(III) and Fe(II) cations, with anions present in a solution due to dissociation of the acids. The active concentrations of Fe(III) and Fe(II) cations in these systems change non-equally, which affects the redox potential of a system. The deviation of a system’s redox properties from the Nernst equation is the stronger the higher the complexing ability of the ligands formed from the acid. The greatest deviation of the experimentally determined values of the electrode potential of the Fe(III)/Fe(II) redox couple from those calculated using the Nernst equation based on the reference value of the standard electrode potential of this redox couple (E°Fe(III)/Fe(II) = 0.771 V (25°С)) is observed in environments containing H3PO4.
Corrosion of structural metal materials in liquid high-temperature salt melts is a key problem for many modern and promising technologies: nuclear energy, production by electrolysis of almost all metals and their alloys, including rare earths, semiconductors, nanostructured materials and carbon nanotubes. The melts of halide salts have high corrosion aggressiveness to the structural material. Corrosion process in molten salt media is predominantly redox in nature, therefore electrochemical methods are widely used to study processes and control technological processes in salt melts. The redox potential is the main method of current control of hightemperature salt melts, corrosion of structural materials, impurities and fission products. Dynamic electrochemical methods of corrosion research and control are widely used, such as voltammetry, impedance spectroscopy, and others. Electrochemical devices and software developed by Frumkin Institute of Physical Chemistry and Electrochemistry Russian Academy of Sciences of are useful for scientific research and control of a variety of technological processes, including for monitoring the corrosion state of structural materials in salt melts.
The article discusses the possibility of hydrophobization of the metal surface as a way to reduce their corrosion in an aggressive environment. The effectiveness of hydrophobic treatment depends on the metal, the hydrophobic reagent and the solvent. In some cases, passivation of metals is possible. Formation of a thin hydrophobic protective coating on metals is carried out not only from organic, but also from aqueous solutions, in which chemisorption of the hydrophobic agent plays an important role. The possibility of increasing the stability of the hydrophobic surface of the aluminum alloy AMg6 and its passive state during treatment with an aqueous solution of sodium oleyl sarcosinate with the addition of aminoethylaminopropyltrimethoxysilane is shown. Methods of copper hydrophobization and its protection with triazoles, thiazoles and mixed corrosion inhibitors based on them, as well as alkanethiols are considered.
Copper and its alloys are widely used in industry due to their high electrical conductivity, thermal conductivity, and plasticity. However, in some neutral environments, copper undergoes corrosion, which degrades its functional properties and reduces its service life. Methods of protecting it from corrosion include treatment with inhibitors, but their environmental safety raises concerns. A promising approach is the creation of superhydrophobic (SHP) coatings, which is why we have studied the formation of SHP coatings on copper using alkylmalonic acids (AMAs) as environmentally friendly hydrophobizing agents. The copper surface was preliminarily structured using laser ablation technique to create multimodal roughness, after which it was modified with solutions of AMAs with alkyl chain lengths of C13 and C16. The resulting coatings exhibited superhydrophobic properties with contact angles (Θc) comparable to those of coatings based on stearic acid (C17). Additional rinsing in isopropanol with ultrasonic treatment increased Θc for AMAs but had no effect on stearic acid (SA). Tests under moisture condensation and in chloride-containing solutions confirmed the high protective efficiency of C16 AMA-based coatings, which was close to that of stearic acid. It was found that increasing the temperature of the hydrophobizing solution to 60°C or adding low concentrations of corrosion inhibitors (e.g., 0.1 mmol/ L 1,2,3-benzotriazole) enhanced the stability of the SHP coatings. The results demonstrate that alkylmalonic acids, especially those with long alkyl chains, can serve as an effective and environmentally friendly alternative to traditional hydrophobizing agents for protecting copper against corrosion.
