Recently, it has been shown that superhydrophobic coatings represent a promising and highly effective approach for protecting metals and alloys from corrosion. Although their practical application is currently rather limited due to the complexity of their production and the high cost of reagents, the search for affordable and environmentally friendly methods of surface hydrophobization is of great importance. It is widely known that alkyl carboxylates, especially their higher homologs, are effective passivating agents and corrosion inhibitors for various metals, including aluminum alloys. This review discusses methods for obtaining superhydrophobic coatings on aluminum alloy surfaces by first creating a rough surface texture (via chemical etching, anodizing, laser texturing, or mechanical treatment), followed by modification using non-toxic stearic acid in ethanol and aqueous-ethanol solutions.
The multifunctional properties of steel coatings based on waste motor oil (WMO) and zinc fillers with varying particle diameters have been investigated using PC-1 (3–7 μm) and PCR-1 (25–40 μm) zinc powders as examples. It was found that the density of the oil compositions increases with the concentration of zinc powders, particularly in the presence of PCR-1. Conversely, moisture permeability decreases, showing a more pronounced drop with the addition of PC-1. The latter is only slightly affected by an increase in relative air humidity from 75 to 100%. The kinematic viscosity of the compositions depends minimally on the zinc particle size. An increase in zinc particle size reduces the negative potential shift of the coated steel electrode in a chloride solution; however, the potential for galvanic (sacrificial) protection is maintained at a Zn concentration of 40–60 wt %. The addition of Zn powder to WMO leads to an enhanced protective efficiency of the composition in a 0.5 M NaCl solution and a humidity chamber, which is more significant when using PC-1 zinc and depends weakly on the zinc concentration within the 40 to 60% range. Under atmospheric field conditions, the protective effect of the oil compositions filled with PC-1 and PCR-1 is practically identical, reaching 92–93% after three-month trials.
The Kolmogorov Erofeev topochemical equation was used to analyze the experimental kinetic dependencies of the thickness of conversion coatings on the exposure time in a chromate free alkaline molybdate solution modified with various oxidizing agents and corrosion inhibitors. The samples were made of aluminum alloy B95 and had undergone pre treatment at temperatures T1, T2, and T3. For the first time, it has been shown that the anamorphoses of kinetic curves are linear, and the high values of the approximation reliability (R2) of all anamorphoses confirmed the adequacy of the used equation. The results of the kinetic analysis show that for the T1 heat treatment mode, the process of forming a chromium free conversion coating is controlled only by diffusion, while for the T2 and T3 modes, the values of the n parameter from the Kolmogorov Erofeev equation, which indicates the limiting stage of the process, are 1.12 and 1.04, respectively, indicating that the kinetic and diffusion mechanisms in these cases occur in parallel.
One of methods of solution to the problem of improper disposal of pharmaceuticals is the use of drugs as metal corrosion inhibitors. This study assessed the inhibitory efficacy of expired Pentoxifylline against the corrosion of St3 steel in 1 N HCl and H2SO4 solutions. At room temperature, the drug (200 mg/L) exhibits a protective effect of 83 and 76%, respectively, according to gravimetric data. Introduction of the drug with the KCNS additive increases the protective effect to 98 and 91%, respectively. The addition of KI increases the protective effect to 88% only in a sulfuric acid medium. Pentoxifylline and its combination with KCNS inhibit hydrogen diffusion into steel in the solutions studied.
The combined use of sodium tridecanoate (NaC13) with PEG-115 on copper alloy in neutral chloride solutions was studied using adsorption, polarization, and gravimetric methods. Polarization measurements showed that exposure of MNZh5-1 to an inhibited solution for 18 hours shifts the local depassivation potential of MNZh5-1 positively, more so than without exposure. Corrosion test results show that 0.5 mmol/L NaC13+5.0 mg/L PEG-115 provides complete protection of the alloy in a 0.001 mol/L NaCl aqueous solution, while in a 0.01 mol/L NaCl solution, complete protection occurs at 4.5 mmol/L NaC13+5.0 mg/L PEG-115. Preliminary exposure of the alloy to an inhibited solution reduces the concentration required for complete protection of the alloy: from 4.5 to 2.0 mmol/L NaC13+5.0 mg/L PEG-115 in a 0.01 mol/L NaCl aqueous solution.
Aluminum alloys with a high magnesium content exhibit good strength propertiesbut a higher content of magnesium containing intermetallic compounds can reduce their corrosion resistance in chloride-containing environments. One way to enhance their protective properties is to applycoatings using chemical oxidation. In this study, we investigated various concentrations of sodium molybdate as the main component for creating ultra-thin protective coatings on AMg6 alloy. It was shown that the resulting coatings can effectively adsorb acorrosion inhibitor during the sealingprocess; however, a structure with higher adsorption properties can only be achieved by introducing modifying additives into the oxidation solution. Among the additives studied, EDTAand its combinations with other additives demonstrated the best results, which is likely due to the homogenization of the oxide composition of the resulting coatings.
Coatings were deposited on samples steel alloy St20 based on powders Al2O3, BrAZhNMts 8.5-4-5-1.5, ADM Ni-72 (NiCrBSi), and WC-Co-Cr by detonation gaseous spraying. A comprehensive assessment of their structural and phase characteristics, as well as their physical, mechanical, and tribological properties, was carried out. X-ray structural analysis and electron microscopy were used to determine the phase composition of the coatings: Al2O3 — α- Al2O3, γ- Al2O3 and δ-Al196O288N4; BrAZhNMts — Cu, Al, Fe; ADM Ni-72 — Ni, Ni3B, Ni3C, Ni4B3, Ni23B6; WC-Co-Cr — WC, W2C, W, Co. Coatings microhardness HV0.2 were measured for BrAZhNMts – 267±60 kgs/mm2, WC-Co-Cr – 1360±109 kgs/mm2, Al2O3 – 1285±121 kgs/mm², ADM Ni-72 – 728±48 kgs/mm². The bond strength is maximum for WC-Co-Cr – 130±20 MPa and minimum for Al2O3 – 37±6 MPa; ADM Ni-72 and BrAZhNMts are 92±15 MPa and 50±10 MPa, respectively. It has been shown that an intermediate sublayer of WC-Co-Cr increases the adhesion of BrAZhNMts to 120±15 MPa and that of Al2O3 to 60±11 MPa. Tests on abrasive wear using the Taber method (1000 cycles) revealed the minimum mass loss for WC-Co-Cr – 31±3 mg and the maximum for BrAZhNMts – 147±11 mg; Al2O3 and ADM Ni-72 showed 50±5 mg and 88±7 mg, respectively. A direct correlation has been established between microhardness and wear resistance, while the brittleness of the ceramic reduces the effectiveness of its hardness. The following application recommendations are substantiated: WC-Co-Cr — for protection against abrasive wear; ADM Ni-72 — for corrosive media at high temperatures; Al2O3 — for thermal protection under wear conditions; BrAZhNMts — for restoring mounting surfaces and antifriction units. The results of the work can be used in developing technological recommendations for the implementation of detonation coatings in the oil and gas and mechanical engineering industries.
The study examined the effect of pipe wall shear stress (WSS) on the efficiency of inhibitor protection of steel pipelines against CO2 corrosion. It was established that at the initial stage (24 h), the critical shear stress causing film detachment is 8–16 Pa. However, under prolonged exposure (360 h) at 16 Pa, the protective effect recovers to 73.2%, owing to synergy between the inhibitor and inorganic corrosion products. At an extreme WSS of 26 Pa, a hydrodynamic anomaly was identified: intensification of mass transfer promotes the formation of a maximally dense protective film, which reduces the corrosion rate to an absolute minimum (0.019 mm/year).
An overview of the work in the field of chemical-catalytic nickel plating, carried out mainly in the Laboratory of the structure of the surface layers (A. N. Frumkin Institute of Physical chemistry, RAS). The chemical bases of the processes, the compositions of solutions, the conditions of deposition, as well as the dependence of the composition, structure and properties of coatings on factors such as the composition of the solution and temperature are considered. The effect of heat treatment on the structure and properties of the resulting materials is also discussed. To get a fairly complete picture, the authors have included in the list of references several other most significant works in this field.
