Прегледај по Аутор "Tomić, Milorad V."
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- СтавкаEffect of Temperature on the Corrosion Inhibition of Nonionic Surfactant TRITON-X-405 on Ferritic Stainless Steel in 1.0 M H2SO4(American Chemical Society, 2012) Fuchs-Godec, Regina; Pavlović, Miomir G.; Tomić, Milorad V.The inhibiting action of a nonionic surfactant of the TRITON-X series (TRITON-X-405) on stainless steel type X4Cr13 in 1.0MH2SO4 solution within the temperature range of 25!45 !Cwas studied using the gravimetric and potentiodynamic technique. The inhibition efficiency was found to increase with the inhibitor concentration and decrease with temperature. The satisfactory inhibition efficiency of TRITON-X-405 on SS type X4Cr13 in 1.0MH2SO4 was limited to temperatures below 35 !C or at the surfactant concentration higher than c = 10!5 M. The adsorption of TRITON-X-405 on stainless steel type X4Cr13 in one molar of sulphuric acid within the chosen temperature range follows the Flory!Huggins adsorption model with very high negative values of the free energy of adsorption ΔGads. The thermodynamic parameters, such as the heat of adsorption and adsorption entropy, were calculated by employing thermodynamic equations. Activation parameters such as apparent activation energy, activation enthalpy, and activation entropy were evaluated from the effect of temperature on corrosion and inhibition processes. Those entire apparent activation parameters show an increase!decrease characteristic (a nonmonotonic function). They increased at concentrations lower than the cmc of added surfactant and decreased when the concentration of TRITON-X-405 was higher than c = 10!5 M.
- СтавкаEffect of α-tocopherol as a green inhibitor on chloride induced corrosion of steel(Elsevier, 2019) Fuchs–Godec, Regina; Tomić, Milorad V.; Pavlović, Miomir G.Immersion of stainless-steel (SS) samples of type X4Cr13 in ethanol solutions of stearic acid, with and without addition of α-tocopherol, resulted in a modified surface with hydrophobic and corrosion resistance characteristics. We observed a double effect: a hydrophobic and corrosion-resistant surface of SS type X4Cr13 in a solution of 3.0% (wt.) NaCl at 25ºC. The corrosion properties of bare and modified surfaces of stainless steel were tested by polarization and electrochemical impedance spectroscopy (EIS) in 3.0% (wt.) NaCl solution at 25°C. To observe the morphology and microstructures of sample surfaces, a Scanning Electron Microscope (SEM) was used after the electrochemical measurements. The results obtained from potentiodynamic polarisation measurements show that the inhibition effectiveness of X4Cr13 reached ≈ 68% in cases when surfaces were modified in stearic acid alone (EIS measurements ≈ 82%), while the values increased to more than 99.0% (for both methods) with addition of α-tocopherol (E307). Modification of the surface using an immersion method in an ethanol solution of stearic acid, especially with addition of α-tocopherol, appears to be a promising treatment for improving the corrosion resistance of stainless steel (SS) X4Cr13.
- СтавкаHardness and corrosion resistance of Zn−Mn/Al2O3 composite coatings produced by electrochemical deposition(National Institute of Science Communication and Policy Research (CSIR-NIScPR), 2022) Bučko, Mihael; Riđošić, Marija; Kovačina, Jovanka; Tomić, Milorad V.; Bajat, Jelena B.The aim of this study is development and characterization of the novel Zn-Mn/Al2O3 composite coatings. The coatings were electrodeposited with constant current density on steel, from chloride solution, without any commercial additives. The Zn−Mn alloy coatings that show high corrosion resistance, may be used in future as an alternative to cadmium coatings. However, the pure Zn and Zn alloy coatings are characterized with poor mechanical properties. Therefore, in this work the alumina particles were incorporated into the Zn-Mn matrix, and the hardness and corrosion resistance of the obtained composite coatings were tested. The mechanical and ultrasound agitation were used to achieve good dispersion of plating solution and homogeneous co-deposition of second phase. The goal was to examine the effect of the agitation type in bath, on the attributes of the deposited composite coatings. The incorporation of Al2O3 particles was enhanced when the mechanical agitation of the solution was applied. However, in case that this agitation method was used, the agglomeration of the alumina particles occurred. In contrast, when an ultrasonic agitation of the plating solution was applied, the uniform distribution of the alumina particles could be achieved. The presence of particles in the matrix, along with applied ultrasound, resulted in grain refinement and homogeneous microstructure. The Al2O3 nanoparticles incorporated in Zn-Mn alloy matrix, resulted in a significant increment in the indentation hardness and a modest increase in the coating corrosion resistance. However, the coating hardness increased with alumina addition, only in case when an ultrasonic agitation of the electrodeposition solution was used.
- СтавкаIspitivanje prevlaka Zn–Co legura dobijenih pulsirajućom strujom(Association of the Chemical Engineers of Serbia, 2012) Bajat, Jelena B.; Maksimović, Miodrag D.; Tomić, Milorad V.; Pavlović, Miomir G.Ispitivano je elektrohemijsko taloženje cink–kobalt legure pulsirajućom strujom na čeliku, a s ciljem dobijanja zaštitnih prevlaka sa povećanom korozionom stabilnošću. Prevlake legura su taložene pulsirajućim režimom sa različitim srednjim gustinama struje i pri različitom trajanju katodnog pulsa. Analiziran je uticaj ovih parametara na iskorišćenje struje prilikom elektrohemijskog taloženja na izgled prevlaka (snimanje elektronskim mikroskopom), hrapavost prevlaka i njihovu korozionu stabilnost u 3% NaCl (merenjem slobodnog korozionog potencijala u agensu korozije i snimanjem polarizacionih krivih). Pokazano je da u zavisnosti od vremena pulsa, prevlake taložene pulsirajućim režimom mogu da imaju bolju homogenost, sitnije aglomerate kristalnih zrna i manju hrapavost od onih taloženih pri istim uslovima, ali konstantnom gustinom struje. Veću korozionu stabilnost pokazale su prevlake legura taložene većom srednjom gustinom struje.
- СтавкаSpecifičnosti elektrohemijskog taloženja i morfologija Zn–Mn prevlaka dobijenih iz pirofosfatnog elektrolita(Association of the Chemical Engineers of Serbia, 2011) Bučko, Mihael M.; Stevanović, Sanja I.; Tomić, Milorad V.; Pavlović, Miomir G.; Bajat, Jelena B.U proteklih nekoliko godina pokazano je da se alkalni pirofosfatni elektrolit može primeniti za elektrohemijsko taloženje prevlaka Zn−Mn legura na čeliku. U ovom radu je ispitana zavisnost morfologije i hemijskog sastava Zn−Mn prevlaka od primenjene gustine struje taloženja. Karakterizacija prevlaka vršena je mikroskopijom atomskih sila i energetskom disperzionom atomskom analizom. Metodom linearne voltametrije ispitan je uticaj dodatka, askorbinske kiseline, na katodne procese. Utvrđeno je da se iz alkalnog rastvora mogu dobiti prevlake zadovoljavajućeg kvaliteta, ali da gustina struje ima veliki uticaj na homogenost i hrapavost površine Zn−Mn prevlaka. Askorbinska kiselina inhibira redukciju vodonika i povećava iskorišćenje struje za taloženje legure.
- СтавкаThe Inhibitive Effect of Vitamin-C on the Corrosive Performance of Steel in HCl Solutions(Elsevier, 2013) Fuchs–Godec, Regina; Pavlović, Miomir G.; Tomić, Milorad V.The inhibitive behaviour of Vitamin C (ascorbic acid), as a type of green inhibitor, on the corrosive behaviour of stainless-steel (SS) X4Cr13 within an aqueous solution of hydrochloric acid (HCl) was studied within a concentration range of 0.01 – 5.0 M HCl. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS), was used for the measurements at 25 °C. The polarization curves revealed that the studied mixtures of the chosen inhibitor represented mixed-type of the inhibitor. A good inhibitive efficiency for Vitamin C at chosen concentration of 10-2 and 10-3 mol L-1 on the SS type X4Cr13 in HCl was limited to concentrations of HCl below 1.0 mol L-1.
- СтавкаThe Inhibitive Effect of Vitamin-C on the Corrosive Performance of Steel in HCl Solutions - Part II(Elsevier, 2015) Fuchs–Godec, Regina; Pavlović, Miomir G.; Tomić, Milorad V.The inhibitive behaviour of Vitamin C, as a type of green inhibitor, on the corrosive behaviour of stainless-steel (SS) X4Cr13 within an aqueous solution of hydrochloric acid (HCl) was studied at concentration of c= (0.01, 0.1 and 1.0) mol L-1. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS), was used for the measurements at 25 °C. To observe the morphology and microstructures of sample surfaces, after the electrochemical measurements a Scanning electron microscopy (SEM) was used. On the basis of the EDAX analysis within the solution of hydrochloric acid (0.01 mol L-1) with addition of Vitamin-C (0.005 mol L-1)the presence of the feri-chelates on the metal surface could be confirmed. The polarization curves revealed that the studied mixtures of the chosen inhibitor represented mixed-type of the inhibitor. The results show that the inhibition efficiency increases with the increase of the inhibitor concentration. This valid especially in the case of the lowest concentration of HCl (c=0.01 mol L-1). In addition to this at higher HCl concentration (c=1.0 mol L-1) the immersion time has a noticeable influence on the inhibitive response. Furthermore, the results obtained in this study showed that the inhibitory effect of Vitamin-C to a great extent on electrode potential.