Atmospheric corrosion, which occurs across various industrial sectors including the military, agriculture, oil and gas, as well as in everyday life, is a widespread form of corrosion and causes significant economic losses in the metals industry (Kusmierek and Chrzescijanska 2015; Roberge et al. 2002; Santa et al. 2022; Syed 2006). Consequently, most metallic materials are exposed to the aggressive effects of the atmosphere, which contains corrosive agents such as oxygen, carbon dioxide, water vapor, aerosols of sea salts, industrial gases, and solid particles, and therefore undergo corrosion (Alcantara et al. 2017; Sabir and Ibrahim 2017; Syed 2006; Vidal et al. 2019). In recent years, atmospheric corrosion has gained increased attention from the materials science community, as it accounts for a higher incidence of failures – both in terms of tonnage and associated costs than any other form of environmental corrosion (Al-Moubaraki and Obot 2021; Mohn 1989; Yang et al. 2017; Zeng et al. 2025).

Carbon steel, galvanized steel, and aluminum are among the most commonly used metals in the construction industry. Of these, carbon steel tends to corrode the quickest, with a corrosion rate that can be 5 to 20 times higher than that of galvanized steel, depending on environmental conditions, and in more aggressive atmospheres can reach values of 100 times or more than that of aluminum over time (Natesan et al. 2006; Priyotomo et al. 2020; Santa et al. 2022; Vashi and Kadiya 2010). Steel remains the most frequently used metal in outdoor structures due to its low cost and strong mechanical properties, making it ideal for a variety of structural applications. The widespread use of carbon steel has made its corrosion behavior a central topic for corrosion engineers and electrochemists, and its atmospheric corrosion has been extensively studied in numerous research articles (Di Sarno et al. 2021; Paterlini et al. 2024; Soriano and Alfantazi 2016; Xie et al. 2017).

Classification and influencing factors. There are various types of atmospheric environments, each characterized by different temperatures, relative humidity levels, pollutant concentrations, and other environmental conditions – all of which influence the rate and nature of corrosion (Cai et al. 2020). Depending on the degree of surface moisture, atmospheric corrosion can be classified into dry, damp, and wet types (Landolfo et al. 2010).

Relative humidity. Atmospheric corrosion becomes an electrochemical process when an aqueous adlayer forms on the metal surface at ambient relative humidity levels exceeding the critical humidity. This critical threshold governs the formation of a continuous electrolyte film, which enables efficient oxygen depolarization and thereby promotes electrochemical corrosion at an accelerated rate (Cai et al. 2020; Lin and Chen 2018; Wang et al. 2015). Thus, in the absence of atmospheric pollutants, steel exposed to environments at or above the critical relative humidity undergoes corrosion through the electrochemical mechanism described by the relevant anodic and cathodic reactions:

Anodic reaction: 2Fe → 2Fe²⁺ + 4e⁻

Cathodic reaction: O₂ + 2H₂O + 4e⁻ → 4OH⁻

Overall reaction: 2Fe²⁺ + 4OH⁻ → 2Fe(OH)₂

Initially, ferrous ions are produced at the anode, while oxygen reduction occurs at the cathode. The resulting reaction products subsequently combine to form ferrous hydroxide, an insoluble compound at neutral pH that deposits on the metal surface.

In contrast, when the relative humidity falls below the critical level, the corrosion process slows significantly, as no electrolyte film is present. The time of wetness, defined by the presence of an electrolyte film on a metal surface, is a key parameter determining the duration of electrochemical corrosion process. This variable is complex, as it involves the formation and evaporation of the electrolyte solution on the metal surface (Hoseinpoor et al. 2020). Therefore, relative humidity is the most influential environmental factor affecting atmospheric corrosion, and its effects vary significantly with geography, season, and time of day (Cai et al. 2020). Several studies have shown that an increase in relative humidity leads to a higher corrosion rate on clean metal surfaces without salt deposits (Feliu et al. 2003; LeBozec et al. 2004; Samie et al. 2007).

The magnitude of atmospheric corrosion is primarily controlled by the duration of surface wetness, and is also influenced by a range of environmental and material factors. Besides relative humidity, these include temperature, solar radiation, rainfall, dew formation, wind speed, and atmospheric pollutants such as chlorides, sulfur oxides and nitrogen oxides. These factors are dynamic and exhibit temporal and regional variability, leading to significant differences in corrosion behavior across geographical locations (Esmaily et al. 2015; Heredia et al. 2024; Leygraf et al. 2016; Morcillo et al. 2015).

Temperature. As described above aqueous precipitation, such as rain and fog, as well as humidity induced condensation (dew) due to temperature changes, are the main promoters of electrolyte formation and, consequently, metallic corrosion (Morcillo et al. 2015). Temperature, along with its changes, is another important factor influencing atmospheric corrosion. When the relative humidity is below the critical relative humidity and no electrolyte film is present, the effect of temperature on corrosion is generally negligible. However, when relative humidity exceeds the critical level, increasing temperature accelerates the corrosion rate. The impact of temperature appears in two principal ways: directly, by influencing the kinetics of corrosion reactions, and indirectly, by affecting the formation and evaporation of the electrolyte film on the metal surface (Cai et al. 2020).

Atmospheric pollutants. Another factor that substantially influences the intensity of corrosion is the chemical composition of the atmosphere, including air pollution caused by gaseous emissions, acid vapors, and seawater aerosols. Almost all atmospheric components affect metal corrosion. Although not all impurities are equally corrosive, they can intensify each other’s actions. The primary airborne contaminants contributing to atmospheric corrosion are sulfur oxides, nitrogen oxides, chlorides, carbon dioxide, hydrogen peroxide, hydrogen chloride, ozone, oxygen, hydrogen sulfide, organic acids, and saline particles (Castano et al. 2007; Qu et al. 2002; Syed 2006; Tidblad et al. 2016). The electrolyte film that forms on the metallic surface contains various compounds derived from these atmospheric pollutants, which change the electrochemical characteristics of the corrosion process and, consequently, the kinetics of corrosion, mainly determined by electrochemical reactions occurring within this thin layer. As a result the atmospheric corrosion process involves simultaneous oxidation and reduction reactions, often accompanied by additional chemical reactions in which corrosion products take part. Overall, the presence and concentration of airborne pollutants further accelerate corrosion through the formation of aggressive corrosion products, leading to higher corrosion rates. Additionally, intrinsic properties such as metal composition and the physicochemical nature of corrosion products – rust layers also modulate the corrosion rate (Alcantara et al. 2017; Kim et al. 2004; Li et al. 2025).

Oxygen. Among the corrosive components of the atmosphere, besides water, oxygen has the greatest impact on the atmospheric corrosion process. Its concentration in the electrolyte and the prevailing diffusion conditions become the most important factors determining the rate of atmospheric corrosion. As a natural component of air, oxygen readily dissolves in the thin moisture film on the metal surface, facilitating oxidation reactions and promoting the conversion of ferrous hydroxide into rust (Li et al. 2023; Stratmann and Muller 1994). Experimental studies have shown that higher oxygen concentrations at elevated temperatures accelerate the oxidation and corrosion of iron and its alloys, with oxidation kinetics and scale growth rates increasing significantly as the oxygen partial pressure in the environment increases (Liu et al. 2024; Petrescu et al. 2025).

Clorides and sulfur dioxide. In polluted atmosphere conditions, chlorides and sulfur dioxide are the most common corrosive agents influencing the atmospheric degradation of metals (Qu et al. 2002). The high corrosivity of chlorides and sulfur dioxide arises from their easy incorporation into the thin moisture layers that form on metallic surfaces under atmospheric conditions.

Clorides. Chloride ions are among the most common and significant atmospheric corrosive agents, as reported by numerous researchers worldwide (Alcantara et al. 2015; Askey et al. 1993; Corvo et al. 2005; Enos 2022; Krivy et al. 2017). Those coming from natural airborne salinity, such as marine atmospheres, mainly in the form of aerosols, can deposit on metal surfaces and directly participate in electrochemical corrosion reactions. A high concentration of chloride ions in the aqueous adlayer on the metal surface, combined with high moisture retention in severely corroded rust layers, promotes the formation of ferrous chloride, which then hydrolyzes. Askey et al. (1993) published an interesting study on the corrosion of iron by atmospheric hydrogen chloride, proposing a direct reaction between carbon steel and hydrogen chloride. In this process, hydrogen chloride reacts directly with the metal to form soluble ferrous chloride, which is subsequently oxidized to ferric oxyhydroxide with the regeneration of hydrogen chloride. The overall reactions can be represented as follows:

Fe + 2HCl + O₂ → FeCl₂ + H₂O

2FeCl₂ + 3H2O + O₂ → 2FeOOH + 4HCl

Recent researches investigating the wetting behavior of metal surfaces have provided insights into the processes controlling atmospheric corrosion, particularly concerning the influence of relative humidity on steel corrosion in the presence of sea salt aerosols such as NaCl and MgCl₂ (Cole et al. 2004; De la Fuente et al. 2016; Ericsson 1978; Schindelholz et al. 2014a, b). Thus, sea salt, primarily originating from the oceans, is an important atmospheric contaminant, particularly contributing to the corrosion of carbon steel structures. Ericsson (1978) demonstrated that sodium chloride particles deposited on a carbon steel surface can initiate corrosion at relative humidity levels previously considered too low to induce sulfur dioxide related corrosion. He further reported that the synergistic interaction between sodium chloride and sulfur dioxide at 90% relative humidity increased the corrosion rate of carbon steel by approximately 14 times compared with that caused by sodium chloride alone.

Studies (Lin and Wang 2005; Lindstrom et al. 2000; Oh et al. 1999; Sica et al. 2007; Wang et al. 2018; Yang et al. 2017) have also shown that chloride deposition increases the corrosion rate of various metals, in addition to carbon steel, including zinc, aluminum alloys, and magnesium alloys. In addition it should be noted that the influence of chloride ions on the corrosion mechanisms of carbon steel has been much less extensively studied than the effect of sulfur dioxide.

Sulfur dioxide. The concentration of sulfur dioxide in the atmosphere, originating mainly from the combustion of fossil fuels containing sulfur, also plays an important role in determining the magnitude of atmospheric corrosion in urban and industrial environments (Smith et al. 2001). In general, high concentrations of sulfur dioxide in the atmosphere result in a corresponding increase in the corrosion rate. When the acidity of polluted atmospheres exceeds a certain level, sulfur dioxide can behave as an oxidizing agent and significantly enhance the cathodic reaction (Cox and Lyon 1994; Klinesmith et al. 2007).

The high solubility of sulfur dioxide, approximately 1000 times greater than that of oxygen in water (Feng et al. 2025) makes it a more effective cathodic reactant than dissolved oxygen, which is the primary depolarizing agent, despite its comparatively low atmospheric concentration. Even rainwater can absorb sulfur dioxide from the atmosphere as it falls, leading to the formation of acid rain. Consequently, rainwater collected downwind of highly industrialized regions often exhibits distinctly acidic pH values (Prakash et al. 2022). Under such conditions, the cathodic hydrogen evolution reaction becomes significant:

2H⁺ + 2e⁻ → H₂

Rozenfeld (1972) showed that sulfur dioxide acts as an active cathodic depolarizing agent because of its high reducibility on metallic surfaces. It is adsorbed on metal surfaces, has a high solubility in water, and in the presence of surface moisture electrolyte layer, undergoes oxidation to produce sulfate ions according to the following reaction (Tullmin and Roberge 2000):

SO₂ + O₂ + 2e⁻ → SO₄²⁻

On iron and steel surfaces, the presence of these sulfate ions contribute to the formation of iron sulfate, which is recognized as one of the primary corrosion products in polluted industrial atmospheres and usually detected within the surface corrosion layer (Huang et al. 2024). Sulfur dioxide participates in the formation and propagation of sulfate nests through its interaction with moisture and oxygen, producing sulfuric acid, which subsequently reacts with iron to produce iron sulfate, according to reactions (Alcantara et al. 2017):

2H₂SO₄ + 2Fe + O₂ → 2H₂O + 2FeSO₄

These sulfate nests initially appear as isolated points on the metal surface and gradually expand until the entire surface becomes covered by a rust film. Hydrolysis of the iron sulfate formed in these nests controls their propagation:

6FeSO₄ + H₂O + 3/2O₂ → 2Fe₂(SO₄)₃ +2FeOOH

Fe₂(SO₄)₃ + 4H₂O → 2FeOOH + 3H₂SO₄

Economic impact. These factors result in substantial, irreversible metal losses, posing a significant economic concern. Industry and academic sources commonly estimate that corrosion necessitates the replacement of roughly one-quarter of global steel production each year (Prosek et al. 2025). In developed countries, the cost associated with controlling metal corrosion is estimated to reach nearly 3–4% of GDP (Gross Domestic Product) (Iannuzzi and Frankel 2022). However, studies indicate that the implementation of corrosion prevention best practices could significantly reduce this financial load.

Techniques for Preventing Atmospheric Corrosion of Metals. There are many technical solutions to protect metals from atmospheric corrosion. The most widely used approach is the application of protective coatings. In particular, organic coatings on steel are a common and highly effective means of controlling rust formation (Lyon et al. 2017; Motlatle et al. 2022; Nazari et al. 2022). Painting represents an additional approach to preventing rust on metal surfaces (Petrunin 2022), though its applicability is limited, as not all metal surfaces can or require painting. Another way of preventing metal corrosion, used in industries where equipment must be stored outdoors after production instead of using closed storage method, which involves high material costs for the construction of garages and hangars, as well as operating expenses for their maintenance is the application of corrosion preventive fluids to protect them against meteorological conditions characteristic of a given area, including solar radiation, temperature and humidity, wind, and precipitation (Maraveas 2020; Schouten and Gellings 1987). Authors of (Vigdorovich et al. 2015) recommend using oil-based corrosion prevention fluids, which have shown high efficiency in protecting metal surfaces even at high concentrations of sulfur dioxide in the atmosphere.

Corrosion preventive fluids. Among the various anti-corrosion measures, corrosion preventive fluids are commonly applied to provide temporary protection by forming barrier films on metal surfaces. An effective temporary corrosion preventive fluid should adhere to the metal surface, form a protective film that ensures uniform coverage over the entire surface against moisture, and inhibit oxidation (Ghanbarzadeh and Akbarinezhad 2006; Kuznetsov and Redkina 2022; Ma et al. 2024; Saji 2020). They protect metallic components from corrosive environmental conditions during transportation or storage across a wide range of applications, including heavy machinery, military equipment, offshore drilling equipment, unfinished pipes, steel consumer products, steel fasteners, coiled steel, vehicle undercarriages, and construction materials. In many cases, corrosion protection is required only during storage prior to the start of production, and in such situations these fluids are particularly preferred because they can be easily removed (Ghanbarzadeh and Akbarinezhad 2006; Ma et al. 2024; Saji 2020; Zhang et al. 2024).

Corrosion preventive fluids are typically prepared by dosing corrosion inhibitors, film-forming agents, and other functional additives into a selected base medium, which constitutes the major portion of the final formulation and is chosen according to the desired film properties (Ghanbarzadeh and Akbarinezhad 2006; Kuznetsov and Redkina 2022; Saji 2020; Tang 2019). These media are:

It should also be noted that water-based corrosion preventives do not effectively displace water, therefore additional cleaning may be necessary to remove coolant residues prior to application.

Asia accounts for roughly half of the global corrosion preventive fluid consumption (Saji 2020), largely due to China’s extensive metal parts export industry, which requires protection during shipping. Solvent- and oil-based fluids dominate both Asian and American markets, while in Europe, where environmental regulations are stricter, water-based corrosion preventive fluids represent about 40% of usage.

Corrosion inhibiting components of preventive fluids. As mentioned above, corrosion preventive fluids, besides the base medium, contain a mixture of additives such as corrosion inhibitors, antioxidants, dewatering agents, and various specialty additives, formulated to achieve an optimal balance between efficiency and cost. The effectiveness of corrosion preventive fluids is significantly improved by the inclusion of corrosion inhibitor additives. As is well known, corrosion inhibitors are chemicals used to protect metallic surfaces. Most of them are organic surface-active compounds soluble in the medium of preventive fluids and usually consist of organic acid salts or related compounds (Aghazada et al. 2019; Saji 2020; Tang 2019). Overall, protection achieved through the application of corrosion inhibitor reagents is widely recognized as a simple and effective method for preventing metal corrosion (Abbasov et al. 2017; Abd El-Lateef et al. 2013; Aslam et al. 2022; Nmai 2004; Puzikova et al. 2025; Raja et al. 2016). Inhibitors act by adsorbing onto the metal surface and forming a protective film, which slows corrosion by affecting anodic and/or cathodic polarization behavior, limiting ion diffusion to the metallic surface, and increasing its electrical resistance (Abd El-Lateef et al. 2012a; Cicek 2017; Hirano et al. 1987; Ma et al. 2022; Shwetha et al. 2024). It is accepted that organic corrosion inhibitors adsorb (via physisorption and/or chemisorption) onto metal surfaces through their polar head groups, while their non-polar tails orient vertically and pack densely, forming a tight protective film (Nmai 2004). In addition, hydrocarbon molecules from the oil-based medium can interact with these non-polar tails through weak van der Waals forces (physisorption), increasing the thickness and effectiveness of the hydrophobic layer. Therefore, matching the chain lengths of the inhibitor and base oil is essential for achieving optimal corrosion prevention (Hirano et al. 1987). There are several characteristics that need to be possessed by an effective corrosion inhibitor, specifically, thermal stability, low cost, and, more importantly, compliance with environmental regulations and standards.

Many researchers around the world are focused on creating environmentally friendly corrosion inhibitors for various applications using cheaper and more accessible natural resources (Abbasov et al. 2012; Abd El-Lateef et al. 2012b; Al-Amiery et al. 2024; Ismayilov et al. 2015; Marzorati et al. 2019). In particular, authors (Abbasov et al. 2012, 2014; Abd El-Lateef et al. 2012b, 2013; Ismayilov et al. 2012, 2014) presented their studies on determining the protective effectiveness of compounds obtained from vegetable oil based materials as corrosion inhibitors. Amines, such as the alkanolamines monoethanolamine, diethanolamine, and triethanolamine, are well known as corrosion inhibitors in various metalworking fluid and lubricant applications. However, these organic amine type corrosion inhibitors are still insufficient for complete rust prevention, and the synthesis of new nitrogen-containing compounds based on them, with remarkable protective effectiveness, is highly desirable. Accordingly, the purpose of this work was to investigate compositions based on mineral oil and a corrosion-inhibitor additive derived from cottonseed oil and the nitrogen-containing compound monoethanolamine, for use as protective coatings for carbon steel against atmospheric corrosion.

The vegetable oil used in the experiments was commercially available product sourced locally.

Monoethanolamine (MEA) was a pure grade chemical produced by the Olaynen Chemical Reagents Factory (Latvia).

Analytical grade diethanolamine (DEA) was supplied by Merck (Germany)

Turbine oil (T-30) was used as a base medium for preparation of the corrosion preventive fluids. The concentration of corrosion inhibiting additive was 5–10 wt.%. The investigated fluids were prepared by simple mixing.

The studies were carried out on samples of carbon steel St10 with a composition, wt.%: C 0.10; Mn 0.50; Si 0.20; P 0.03; S 0.03; Cr 0.10; Ni 0.10; Cu 0.20; Fe balance. The carbon steel plates have a length of 50 mm, a width of 40 mm, and a thickness of 5.5 mm. Before the experiments, the specimen surfaces were successively polished, rinsed with deionized water, and degreased using organic solvent (petrol or alcohol).

The oil-based coatings were deposited by immersion of the plates into the bath containing the corrosion preventive fluid at room temperature for one day. After that, they were kept in a suspended state for an hour to drain off the excess oil composition and to form a protective film.

To investigate the effectiveness of the corrosion preventive fluids, tests were conducted according to GOST 9054-75 under various aggressive conditions simulating the effects of corrosive media: in seawater, in a 0.001% sulfuric acid solution, and in a Q-4 hydro chamber at high humidity (95 ± 3%) and temperature (40 ± 1°C) with periodic moisture condensation. The Q-4 hydro chamber work procedure was as follows: the tests were carried out for 8 hours, after which the chamber was turned off for 16 hours while remaining closed. This cycle was repeated, and periodic visual assessments of the plate surfaces were checked to detect corrosion products.

The parameter used to evaluate the protective properties of the corrosion preventive fluids was the time, in days, until corrosion damage appeared on the surface of the steel plates. For each corrosion preventive fluid, three parallel experiments were performed on samples to ensure the reliability of the results. The tests were stopped as soon as corrosion was observed on any one of the plates.

According to established practice and published studies, corrosion preventive fluids are generally regarded as effective when they provide prolonged protection of steel surfaces under accelerated testing conditions. Consequently, such fluids can be used in a wide range of applications.

The synthesis of monoethanolamides of cottonseed oil fatty acids was carried out via a direct one-step aminolysis process, involving the reaction of cottonseed oil triglycerides with monoethanolamine at different molar ratios (1:1–1:3) at high temperature 120°C for 3 hours. Monoethanolamides synthesized from the reaction of cottonseed oil triglycerides with monoethanolamine were designated according to the molar ratio of the reactants. The product obtained at a 1:1 molar ratio was named MEA1, while those produced at 1:2 and 1:3 molar ratios were labeled as MEA2 and MEA3, respectively. The acid numbers (mg KOH/g) were determined as key properties of the synthesized monoethanolamides. The measured values were 3.19 mg KOH/g for MEA1, 1.05 mg KOH/g for MEA2, and 4.20 mg KOH/g for MEA3. The relatively low acid numbers indicate that the aminolysis reaction proceeded effectively.

The reactions of cottonseed oil triglycerides with monoethanolamine are schematically illustrated for MEA1, MEA2, and MEA3.

Synthesis of the MEA1:

Synthesis of the MEA2:

Synthesis of the MEA3:

The structures of the synthesized monoethanolamides were confirmed using IR spectroscopy. The spectra were recorded on a BRUKER ALPHA FT-IR spectrometer (Germany). Figure 1 presents the IR spectra of the synthesized monoethanolamides derived from cottonseed oil fatty acids, and the assignments of the observed absorption bands are summarized in Table 1.

As seen from the spectra, the absorption bands corresponding to the scissoring, deformation, and stretching vibrations of the C–H bonds in the –CH₂– and –CH₃ groups exhibit nearly identical intensities for all three synthesized monoethanolamides. Similarly, the stretching vibrations of the C–H bonds in the = CH– groups at 3008 cm^− 1 also show the same intensities.

In the aminolysis process, as the molar ratio of the initial reactants (oil:monoethanolamine) increases in the sequence 1:1 → 1:2 → 1:3, a decrease is observed in the intensities of the absorption bands corresponding to the stretching vibrations of the C–O–C bonds at 1160 cm^− 1 (a), 1164 cm^− 1 (b), and 1169 cm^− 1 (c), as well as the C = O bonds at 1742 cm^− 1 (a), 1742 cm^− 1 (b), and 1740 cm^− 1 (c) in the ester groups.

Along this sequence, the absorption bands assigned to the stretching vibrations of the C–O bonds in the C–OH fragments, which indicate the formation of alcohol in the reaction medium, shift to lower frequencies at 1068 cm^− 1 (a), 1060 cm^− 1 (b), and 1050 cm^− 1 (c), accompanied by an increase in their intensity. At the same time, the broad absorption bands in the 3100–3600 cm^− 1 region, corresponding to the O–H stretching vibrations of the hydroxyl groups that also signify alcohol formation, become more pronounced as the molar ratio increases during the amidation process.

The increase in intensity was also recorded in the absorption bands of the stretching vibrations of the C = O bonds at 1656 cm^− 1 (a), 1652 cm^− 1 (b), and 1642 cm^− 1 (c), the deformation vibrations of the N–H bonds at 1535 cm^− 1 (a), 1545 cm^− 1 (b), and 1560 cm^− 1 (c), and the stretching vibrations of the N–H bonds at 3410 cm^− 1 (a), 3383 cm^− 1 (b), and 3296 cm^− 1 (c), in the order MEA1 → MEA2 → MEA3, confirming the formation of amide groups.

The interpretation of the spectra proves that, during the process, the ester groups are replaced by amide groups. Additionally, depending on the molar ratio of the initial substances, monoglyceride, diglyceride and glycerin molecules are formed in the medium, to which the observed alcohol groups can be attributed.

Atmospheric corrosion is a serious problem in various industrial sectors, including oil and gas, defense, machinery manufacturing, and agriculture, as well as in everyday applications, affecting approximately 25% of global iron production and causing significant economic losses. Among the factors determining its aggressiveness, relative humidity, temperature, and atmospheric composition can be particularly noted. Depending on the moisture level of the metal surface, corrosion can be classified as dry, damp, or wet. The main aggressive components driving corrosion processes on metal surfaces are oxygen, chlorides, and sulfur dioxide present in the atmosphere.

Among the methods of protecting metal equipment from atmospheric corrosion for a certain period of time, in addition to technical solutions such as storage in hangars, the application of special anti-corrosion coatings on surfaces is well known, of which the use of corrosion preventive fluids is more effective. Corrosion preventive fluids can be classified into three types: water-based, solvent-based, and oil-based. Their preparation involves the use of one or more components in varying amounts, one of which is corrosion inhibitors.

Nowadays, special attention is given to the synthesis of such reagents based on environmentally friendly raw materials. In this study, monoethanolamides were synthesized through the reaction of cottonseed oil and monoethanolamine at various molar ratios (1:1–1:3), key indicators characterizing the progress of the reaction were determined, and the structures of the synthesized compounds were confirmed by IR spectroscopy. At this time, it was observed that the intensities of the peaks belonging to the ether groups decreased, while the intensities of the peaks belonging to the amide groups, as well as the hydroxyl groups in the glycerides and glycerol, increased.

The synthesized monoethanolamides were added to T-30 turbine oil at concentrations of 5% and 10% to prepare the compositions, and their key physicochemical properties were investigated. Effectiveness of the compositions as corrosion preventive fluids was evaluated on carbon steel St10 plates under aggressive conditions, including a Q-4 hydro chamber, seawater, and a 0.001% sulfuric acid solution. Samples exhibiting high protective performance under these conditions were identified, and the compositions prepared with their addition to T-30 turbine oil in 10% amounts were more active.

The results were compared with those of our previous studies involving ethanolamides synthesized from cottonseed oil and diethanolamine, as well as from sunflower oil and ethanolamines, and general formulas were established for the protective efficiencies of such compounds. Thus, ethanolamides synthesized on the basis of sunflower oil as raw material exhibited higher protective efficiency than those synthesized based on cottonseed oil, while diethanolamides were superior to monoethanolamides in terms of protective activity. The sequence of effectiveness according to the molar ratio of the initial materials was 1:1 < 1:2 < 1:3. In certain cases where these formulas were not strictly followed, the differences in activity between the samples were insignificant. The observed research results are scientifically justified. Consequently, the higher activity of ethanolamides synthesized based on the sunflower oil as a raw material is attributed to the greater degree of unsaturation in the fatty acids, the higher activity of diethanolamides compared to monoethanolamides is explained by the presence of an additional hydroxyl group in the molecule, and the increased number of amide groups in compounds formed at higher molar ratios also contributes to their enhanced protective efficiency.