Several directions of metal corrosion inhibition are considered, which are combinations of an inhibitor (CI) with either other CI, or with cathodic protection, or with a thin protective coating, for example, superhydrophobic.

The paper investigates stress corrosion cracking (SCC) of X70-grade pipe steel under conditions simulating the underground service of main gas pipelines. Corrosion-mechanical tests were performed on specimens cut from pipes by cyclic four-point bending (maximum stresses were close to the yield strength) in electrolytes with different capacities to promote hydrogen uptake. NS4 solution, simulating the electrolyte beneath a disbonded coating, and a citrate buffer at pH 5.5 were used as model near-neutral media. The degree of hydrogen charging was increased by adding a hydrogen-uptake promoter (thiourea) and by varying the potential. It is shown that microcracks initiate at the bottom of stress concentrators (pits) and then emerge on the specimen surface, forming narrow cracks with a high aspect ratio. The corrosive medium shortens the incubation period of crack formation by approximately a factor of two compared with air, while the time to crack initiation is determined by the size and shape of the concentrator: natural pits with diameters on the order of hundreds of micrometres promote crack formation within 24 – 28 days, whereas artificially produced holes 0.6– 1 mm in diameter initiate cracks within 5 – 7 days. Based on hydrogen permeability measurements (electrochemical desorption), ranges of hydrogen concentration in the near-surface layer were estimated in which the effect of hydrogen on SCC initiation becomes noticeable. Under moderate hydrogen charging, crack initiation is hardly accelerated, whereas at elevated hydrogen concentrations in the steel the crack-initiation incubation period decreases sharply. The possibilities of inhibiting SCC by organosilicon (organosilane) films formed on the surface of pipe steel during its modification with solutions of organosilane-based compositions (vinyl- and aminosilanes) and with solutions of mixtures of organosilane + organic corrosion inhibitor (benzotriazole (BTA), Catamine AB) were also studied. The greatest increase in the time to crack initiation (incubation period), together with a decrease in crack growth rate, was achieved using the most effective composition, vinylsilane + benzotriazole. For unprotected steel, a crack emanating from a 1 mm hole appeared after 5 days, whereas in the presence of the surface layer [VS + BTA] it appeared after 36 days; in addition, the crack growth rate at the initial stage of crack development was reduced. The results may be useful for improving the reliability of underground pipelines and for advancing above-ground methods of corrosion diagnostics for underground structures.

The article continues a series of publications dealing with the migrating corrosion inhibitor HAENYTEX Protectoseal Ci for steel reinforcement in concrete. The ability of migrating inhibitors of various brands to protect reinforcing steel against chloride-induced corrosion is analyzed by corrosion-electrochemical methods. The data obtained indicate that Sika Ferrogard-903, IFKhAN-80, and HAENYTEX Protectoseal Ci manifest high and comparable efficiency. MCI 2020 is inferior to all the migrating inhibitors mentioned above.

A comparison of adsorption, protective and passivating properties of sodium salt derivatives of malonic acid on copper and zinc in neutral chloride solutions was carried out. The free energy of adsorption and the protective effect on copper and zinc increase depending on the number of carbon atoms in the alkylsubstituent of the sodium malonate derivative. In corrosion studies, an inverse relationship was obtained between the length of the alkylsubstituent in the structure of the sodium malonate derivative and the degree of zinc protection in a 0.01 mol/L chloride aqueous solution for 7 days. Thus, for copper, with increasing hydrophobicity, the degree of protection by sodium alkylmalonate in a 0.01 mol/L sodium chloride solution increases. In zinc, on the contrary, the degree of protection for the C₉-substituent is lower than for the C₂-substituent.

The replacement of toxic chromate compounds of chemical oxidation of aluminum alloys is an urgent task. One of the ways to achieve high efficiency of chromate-free conversion coatings is to study the parameters of the oxidizing composition and various additives to it. This article presents the results of a study investigating the effect of treatment temperature on the corrosion resistance of chromate-free conversion coatings formed on D16 aluminum alloy (Russian analogue of AA2024 alloy). The protective properties of coatings obtained at 80°C and 90°C in conversion solutions, with and without the addition of modifying additives 1,2,3-benzotriazole and EDTA-Na2, was evaluated. Through polarization measurements, electrochemical impedance spectroscopy, and corrosion testing, it was determined that increasing the treatment temperature promotes the formation of a coating with superior anticorrosion protection. The introduction of modifiers was found to enhance the protective properties of the coatings. Corrosion tests conducted in a climatic chamber confirm the effectiveness of coatings obtained at 90°C.

The passivation and protective properties of the anti-rust additive V-15/41 and its composition with 2-mercaptobenzothiazole (2-MBT) were studied on metals: St3 low-carbon steel, MNZh5-1 copper alloy in aqueous chloride and borate buffer solutions. Individually, V-15/41 is capable of spontaneously passivating all the metals studied and improving the local depassivation potential in a borate buffer solution supplemented with 0.01 mol/L NaCl. The composition V-15/41+2-MBT (9 : 1) has the highest passivation properties, for which at 8.0 mmol/L the protective effect on St3 is 0.22 V, and on MNZh5-1 at 4.0 mmol/L the protective effect is 0.38 V. In a 0.01 mol/L NaCl solution at 7.0 mmol/L of the composition V-15/41+ 2-MBT (9:1) MNZh5-1 and St3 is completely protected from corrosion destruction.

The researches carried out at the Institute of Physical Chemistry of the Academy of Sciences for more than 50 years in the field of electrodeposition of alloys, the use of surfactants in the production of electroplating coatings and the phenomena of passivity during electrodeposition, as well as work on the application of non-stationary electrolysis in electroplating is reviewed.

The review is devoted to the history of phosphate treatment of metals and alloys, the basis for the industrial application of which was laid by the staff of the Institute of Physical Chemistry of the USSR Academy of Sciences in the first half of the twentieth century. The results of their work were the discovery of a method of accelerated phosphating, which makes it possible to obtain more corrosion-resistant coatings, the development of methods for additional coating treatment, and the creation of a method for express analysis of phosphate films protective properties. The review briefly describes the most popular industrial phosphate treatments, the features of zinc and aluminum phosphate treatment, and provides examples of corrosion studies of phosphate treatment coatings conducted at IPCE RAS.