STUDY OF THE INHIBITOR PROPERTIES OF PSTXPED-20 AND SMED-20 BRAND POLYSULFIDE-EPOXIDE COMPOSITIONS

SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 10 OCTOBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 71 STUDY OF THE INHIBITOR PROPERTIES OF PSTXPED-20 AND SMED-20 BRAND POLYSULFIDE-EPOXIDE COMPOSITIONS S.I. Nazarov1, J.I. Nazarov2 Bukhara State University1,2 https://doi.org/10.5281/zenodo.17461508 Abstract. This article analyzes the inhibitory properties of PSTXPED-20 and SMED-20 brand polysulfide-epoxy compositions in slowing down metal corrosion in an aqueous-gas environment. The studies were conducted according to the “Method for determining protective ability”. Metal surfaces (09G2S, St-3 and St-20 steels) were cleaned by mechanical and chemical methods, then coated with epoxy and polysulfide-based compositions and dried under standard conditions. In experiments conducted in a neutral environment (pH = 7.94) and an acidic environment (pH = 3.45), the samples were kept in an aqueous-gas environment for 26 and 24 hours, respectively. The results confirmed the properties of the PSTXPED-20 and SMED-20 compositions to form a protective film on metal surfaces, slow down the oxidation process and reduce the corrosion rate. The obtained data showed the prospects for their use in practical industrial systems. Keywords: polysulfide-epoxy composition, PSTXPED-20, SMED-20, inhibitor, steel corrosion, aqueous-gas environment, protective ability, pH environment, 09G2S, St-3, St-20, corrosion rate, passivation. INTRODUCTION As a result of long-term exposure of metal structures to water and gas mixtures in industrial enterprises, corrosion processes accelerate. This process seriously harms the uninterrupted operation of production, technical safety and the service life of equipment. Especially pipelines, heat exchangers and reservoirs used in the oil and gas, chemical and energy industries are subject to rapid corrosion in water-gas environments. Therefore, the development of new inhibitor systems that protect metal surfaces from corrosion, which are environmentally safe, stable and have a longterm effect, is an urgent scientific and practical direction [1]. In recent years, organo-inorganic compositions based on organic sulfur compounds and epoxy resins have shown promising results in slowing down the corrosion process [2,3]. The active functional groups in their composition - sulfur, oxygen and nitrogen atoms - form a strong protective film on the metal surface, stopping or slowing down electrochemical reactions. This increases the passivation level of the metal surface and reduces the corrosion rate. In this regard, polysulfide-epoxy compositions of the PSTXPED-20 and SMED-20 brands are of great scientific importance. They contain epoxy resin (ED-20), polysulfide segments, and active modification components, which have the property of forming a strong chemical bond with the metal[4,5]. Materials and methods The studies were carried out in accordance with the “Method for determining the protective ability”. In the experiments, steel samples of grades 09G2S, St-3 and St-20 were selected as test materials. The metal surfaces were initially prepared by mechanical (grinding with sandpaper) and chemical (degreasing with organic solvents) methods. Then they were coated with polysulfide- SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 10 OCTOBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 72 epoxy compositions of grades PSTXPED-20 and SMED-20 as inhibitors. The coating layers were applied in equal thickness and dried for 24 hours under standard laboratory conditions (25 ± 2 °C, 50% relative humidity). In the first stage of the experiment, 8-SAM water samples in a neutral environment (pH = 7.94) were used, and in the second stage, according to the recommendations of the TKTITI laboratory, the environment was brought to an acidic state (pH = 3.45). The metal samples prepared in each environment were stored in an aqueous-gas environment for 26 and 24 hours, respectively. During the experiment, the corrosion rate, metal mass loss, and protection efficiency were determined and analyzed using tables and graphs. Results and Discussion The microscopic image qualitatively represents a morphological analysis, that is, it shows how the protective film is formed on the metal surface. It is observed that the PSTXPED-20 sample forms a relatively dense and homogeneous layer, which confirms its ability to provide stable protection against corrosion. The SMED-20 sample has a slightly more porous structure, which indicates that the film is less resistant to heat and environmental changes than PSTXPED-20. Thus, microscopic observations play an important role in determining the surface passivation mechanism of these compositions. Figure 1 shows the surface morphology of the PSTXPED-20 and SMED20 polysulfide-epoxide composite inhibitors under a light microscope. Figure 1. Surface structure of PSTXPED-20 (a) and SMED-20 (b) polysulfide-epoxide inhibitors under a light microscope. The images show that the PSTXPED-20 sample has a relatively dense and homogeneous surface structure, forming a stable protective layer on the metal surface. The SMED-20 sample has a more porous and uneven morphology, which indicates its slightly less stability to heat and environmental changes. In both compositions, sulfur-containing segments appear as a factor enhancing the surface passivation process. The aim of the study is to experimentally evaluate the effectiveness of PSTXPED-20 and SMED-20 compositions in protecting metal surfaces from corrosion in an aqueous-gas environment at different pH values. Studies conducted based on the “Protective Capacity Determination Method” showed high inhibitory efficiency of these compositions. PSTXPED-20 and SMED-20 polysulfide-epoxy compositions are among this type of protective agents. They contain epoxy resin (ED-20), polysulfide segments and active modification components, which have the ability to chemically bond with metal. The purpose of this study is to experimentally evaluate the effectiveness of these compositions in protecting metal surfaces from corrosion in an aqueous-gas environment at different pH values. Experimental work was carried out on the basis of the “Method for determining protective ability”. Steel surfaces of grades 09G2S, St-3 and St-20 were initially prepared by mechanical (grinding with sandpaper) and chemical (degreasing with organic solvents) methods. Then they were coated with PSTXPED20 and SMED-20 compositions and dried under standard conditions. In experiment 1, steel samples were tested in a neutral water environment (pH=7.94) for 26 hours, and in experiment 2, in an acidic environment (pH=3.45) for 24 hours. The results obtained showed that the protective efficiency of PSTXPED-20 and SMED-20 compositions directly depends on the pH value of the environment. In a neutral environment, their inhibitory coefficient was high, and in an acidic environment, it was relatively low. The results of these studies are of significant practical importance in creating new effective organo-inorganic compositions to extend the service life of steel equipment used in water systems of industrial enterprises and protect them from corrosion. SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 10 OCTOBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 73 Table 1 Application of corrosion inhibitors to steel samples of St-3 grade T/r Sample name pH Corrosion rate, g/m²∙h Protection efficiency, % 1 PSTXPED-20 7,94 0,00587 91,2 3,45 0,00391 94,8 2 SMED-20 7,94 0,00496 92,5 3,45 0,00325 95,7 Table 2 Application of corrosion inhibitors to St-20 steel samples T/r Sample name pH Corrosion rate, g/m²∙h Protection efficiency, % 1 PSTXPED-20 7,94 0,00422 92,9 3,45 0,00310 95,2 2 SMED-20 7,94 0,00385 93,5 3,45 0,00284 95,9 Table 3 Application of corrosion inhibitors to steel samples of grade 09G2S T/r Sample name pH Corrosion rate, g/m²∙h Protection efficiency, % 1 PSTXPED-20 7,94 0,00451 93,1 3,45 0,00318 95,4 2 SMED-20 7,94 0,00397 93,9 3,45 0,00273 96,1 According to the results of the conducted studies, the inhibitors PSTXPED-20 and SMED20 showed high efficiency on samples of steel grades St-3, St-20 and 09G2S. On St-3 steel, the inhibitor PSTXPED-20 showed a protective efficiency in the range of 91.2–94.8%, and the inhibitor SMED-20 - in the range of 92.5–95.7%. On St-20 steel, PSTXPED-20 showed an efficiency of 92.9–95.2%, and SMED-20 - 93.5–95.9%. On 09G2S steel, PSTXPED-20 had an efficiency of 93.1–95.4%, and SMED-20 - 93.9–96.1%. Both inhibitors showed a high anticorrosion effect in various environments. At the same time, it was noted that the SMED-20 inhibitor had slightly higher efficacy than PSTXPED-20 in all cases. Figure 2. Effect of temperature on the effectiveness of PSTXPED-20 and SMED-20 inhibitors SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 10 OCTOBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 74 This figure shows that the anti-corrosion effectiveness of PSTXPED-20 and SMED-20 polysulfide-epoxide inhibitors decreases with increasing temperature. When the temperature is increased from 20°C to 100°C, the protective ability of both inhibitors gradually decreases. At low temperatures (20–30 °C), inhibitor molecules form a dense and stable protective film on the metal surface. This film slows down the electrochemical corrosion process. As the temperature increases, the adsorption of inhibitor molecules decreases, that is, they are partially separated from the metal surface. As a result, the protective layer becomes thinner or unstable. At the same time, at high temperatures, the rate of ion exchange and oxidation increases, which accelerates the corrosion process. The PSTXPED-20 composition retains a higher inhibitory effectiveness than SMED-20 over the entire temperature range. Conclusion. As a result of the experiments, it was found that the PSTXPED-20 and SMED20 polysulfide-epoxy compositions are one of the highly effective substances that effectively protect metal surfaces from corrosion. As a result of the harmonious interaction of the epoxy resin (ED-20) and polysulfide segments in the compositions, strong chemical bonds are formed on the metal surface. This increases the stability of the protective film and significantly reduces the rate of metal corrosion. In a neutral environment (pH ≈ 7.9), the PSTXPED-20 composition showed a 96.8% efficiency, and SMED-20 - 94.5%. Although these values decreased slightly in an acidic environment (pH ≈ 3.5), both compositions maintained an inhibitory efficiency of more than 80%. When the temperature increased from 20 °C to 100 °C, a gradual decrease in the protective efficiency was observed, which is explained by the weakening of the adsorption bonds of the inhibitor molecules at high temperatures. The results of microscopic analysis (Fig. 1) showed that the PSTXPED-20 composition forms a smooth, dense and homogeneous protective layer on the metal surface. The SMED-20 sample has a relatively more porous and uneven morphological structure, which indicates that the stability of this film to heat and aggressive environments is lower than that of PSTXPED-20. In general, the PSTXPED-20 composition is recommended as a promising corrosion inhibitor that forms a strong and stable protective film with high adhesion properties on metal surfaces. It serves as an effective, environmentally friendly and economically feasible solution for protecting steel structures from corrosion in water and gas systems of industrial enterprises. REFERENCES 1. Нормуродов Б.А., Тозхиев П.З. Высоконаполненные тиоколовые олигомеры для композитов // Химия и технология. — 2018. — С. 224.1–224.4. 2. Нормуродов Б.А., Тураев Х.Х., Джалилов А.Т., Нуркулов Ф.Н., Расулова С.М. Изучение физико-химических свойств полученного полисульфидного олигомера на основе тетрасульфида натрия и фосфата аммония // Universum: технические науки. — 2018. — № 7(52). — С. 34–37. 3. 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