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The adsorption, CMC determination and corrosion inhibition of some N-alkyl quaternary ammonium salts on carbon steel surface in 2 M H2SO4
Regina Fuchs-Godec, 2006, izvirni znanstveni članek

Opis: Electrochemical measurements were performed to investigate the effectiveness of cationic surfactants of the N-alkyl quaternary ammonium salt type, i.e. myristyltrimethylammonium chloride (MTACl), cetyldimethylbenzylammonium chloride (CDBACl), and trioctylmethylammonium chloride (TOMACl), as corrosion inhibitors for type X4Cr13 ferritic stainless steel in 2 M H2SO4 solution. Potentiodynamic polarization measurements showed that these surfactants hinder both anodic and cathodic processes, i.e. act as mixed-type inhibitors. It was found that the adsorption of the N-alkyl ammonium ion in 2 M H2SO4 solution follows the Langmuir adsorption isotherm. Plots of log ▫$[/theta$▫/(1-▫$/theta$▫)] versus log▫$c_{inh}$▫ yielded straight lines with a slope, which changed drasticallyat the critical micelle concentration (CMC) of the surfactants studied. Accordingly, the CMC could be accurately determined from these measurements. The calculated values of the free energy of adsorption ▫$/Delta$▫▫$G_{ads}$▫ are, in cases when the charge on the metal surface is negative with respect to the PZC, relatively high what is characteristically for the chemisorption. On the other hand, for positive metal surfaces it is assumed that ▫$SO_4^{2-}$▫ anions are adsorbed first, so the cationic species would be limited by the surface concentration of anions. Accordingly ▫$/Delta$▫▫$G_{ads}$▫ values were lower in this case and the adsorption is due to merely electrostatic attraction, which is characteristically of physisorption.
Ključne besede: electrochemistry, corrosion inhibitors, cationic surfactants, Langmuir isotherm, corrosion kinetic parameters, critical micelle concentration, sulphuric acid
Objavljeno: 30.05.2012; Ogledov: 1132; Prenosov: 16
URL Celotno besedilo (0,00 KB)

Inhibition properties of TRITON-X-100 on ferritic stainless steel in sulphuricacid at increasing temperature
Regina Fuchs-Godec, Gregor Žerjav, 2009, izvirni znanstveni članek

Opis: The inhibiting action of a non-ionic surfactant of the TRITON-X series (TRITON-X-100) on stainless steel type X4Cr13 in 1.0 M H2SO4 solution at five different temperatures was investigated by the potentiodynamic polarisation measurements. The inhibition efficiency has been calculated in the presence and in the absence of the inhibitor. The experimental data suggest that the inhibition efficiency increases with increasing concentration of the TRITON-X-100, and decreases with the increasing temperature. Adsorption of the non-ionic surfactant used here obeys the Flory- Huggins isotherm. The thermodynamic parameters, such as, the heat of adsorption, adsorption entropy, and the adsorption free energy, have been calculated by employing thermodynamic equations. Kinetic parameters, also been evaluated.
Ključne besede: non-ionic surfactants, corrosion inhibitors, sulphuric acid, Flory-Huggins adsorption isotherm
Objavljeno: 31.05.2012; Ogledov: 994; Prenosov: 36
.pdf Celotno besedilo (332,60 KB)

Protection of copper and its alloys using corrosion inhibitor-literature review
Milorad V. Tomić, Miomir Pavlović, Milovan Jotanović, Regina Fuchs-Godec, 2010, izvirni znanstveni članek

Opis: A review of the literature dealing with the electrochemical corrosion of copper and its alloys with purpose to find the most suitable inhibitor for its protection has been done. According to their chemical composition of corrosion inhibitors are divided into inorganic and organic inhibitors. Inhibition of alloying metals are possible (such as the addition of arsenic alloy components in brass, preventing its unzincanization). The paper reviews the theoretical basis of application of inhibitors to protect metals from corrosion as well as an overview of current research application of inhibitorsto protect copper and copper alloys. Benzotriazole (BTA) is most often used corrosion inhibitor for copper and its alloys in acidic and alkaline solution, because of its high inhibition efficiency. The lowest concentration of inhibitor for protection of copper in various solutions was 0.05%, and for the protection of copper in contact with steel is 0.1%. On the surface of copper and brass BTA forms a protective Cu-BTA film. However, BTA is like many other synthesized organic inhibitors is very toxic and if used invery small concentrations. It turnedout that the AETD, AETDA and PTAT good corrosion inhibitors of copper mixed type with the efficiency of inhibition increases with concentration. Due to the adverse effects on the environment, health and other bodies in recent times the focus of researchis transferred to the inhibiting action of biological molecules or mixtures of natural compounds called "Green inhibitors".
Ključne besede: corrosion inhibitors, protection of metals, inorganic inhibitors, organic inhibitors, alloys elements, green inhibitors
Objavljeno: 31.05.2012; Ogledov: 1167; Prenosov: 28
URL Celotno besedilo (0,00 KB)

Effects of surfactants and their mixtures on inhibition of the corrosion process of ferritic stainless steel
Regina Fuchs-Godec, 2009, izvirni znanstveni članek

Opis: The corrosion inhibition characteristics regarding mixtures of cationic/zwitterionic types of surfactant (Myristyltrimethylammonium bromide/Palmitylsulfo-betaineas), and non-ionic surfactant TRITON-X-405 mixed with 1 mM of KBr, as corrosion inhibitors for stainless steel (SS) (type X4Cr13) in aqueous solutions of 2 M H2SO4 were investigated using potentiodynamic polarisation measurements. The polarisation data showed that mixtures of the surfactants used in this study acted as mixed-type inhibitors, adsorbing on the stainless steel surface in agreement with the Flory-Huggins adsorption isotherm. The tensiometric results of this study suggest the existence of a second state of aggregation for zwitterionic/cationic surfactant mixtures. From these values of the free energy of adsorption, which in both mixtures decreased with respect to a single surfactant, we concluded that the adsorption in mixtures was stronger. The mixtures studied here showed good inhibition properties for ferritic stainless steel type X4Cr13 in 2 M H2SO4 solution.
Ključne besede: corrosion inhibitor, cationic surfactant, Zwitterionic surfactant, Flory-Huggins isotherm, Sulphuric acid
Objavljeno: 01.06.2012; Ogledov: 714; Prenosov: 23
URL Celotno besedilo (0,00 KB)

Inhibitory effect of non-ionic surfactants of the TRITON-X series on the corrosion of carbon steel in sulphuric acid
Regina Fuchs-Godec, 2007, izvirni znanstveni članek

Opis: The corrosion inhibition characteristics of non-ionic surfactants of the TRITON-X series, known as TRITON-X-100 and TRITON-X-405, on stainless steel (SS) type X4Cr13 in sulphuric acid were investigated by potentiodynamic polarisation measurements. It was found that these surfactants act as good inhibitors of the corrosion of stainless steel in 2 mol L-1 H2SO4 solution, but the inhibition efficiency strongly depends on the electrode potential. Thepolarisation data showed that the non-ionic surfactants used in this study acted as mixed-type inhibitors and adsorb on the stainless steel surface, in agreement with the Flory-Huggins adsorption isotherm. Calculated Gads values are -57.79 kJ mol-1 for TRITON-X-100, and -87.5 kJ mol-1 for TRITON-X-405. From the molecular structure it can be supposed that these surfactants adsorb on the metal surface through two lone pairs of electrons on the oxygen atoms of the hydrophilic head group, suggesting a chemisorption mechanism.
Ključne besede: electrochemistry, corrosion inhibitors, non-ionic surfactants, Flory-Huggins isotherm, critical micelle concentration, sulphuric acid
Objavljeno: 01.06.2012; Ogledov: 928; Prenosov: 24
URL Celotno besedilo (0,00 KB)

An effect of sodium dodecylsulfate on the corrosion of copper in sulphuric acid media
Regina Fuchs-Godec, Valter Doleček, 2004, izvirni znanstveni članek

Opis: The effect of sodium dodecylsulfate (SDS) on copper corrosion in a solution of 0.5 M H2SO4 + x M SDS was studied using electrochemical polarisation measurements. The critical micelle concentration (CMC) of SDS in 0.5 M H2SO4 is 8 * 10-4 M, and the experimental concentrations of SDS were in the range below and above the CMC. It was found that SDS is a good anodic inhibitor at lower anodic overpotentials, i.e. very close to the rest potential. Adsorptionof the inhibitor obeys the Langmuir isotherm. Plots of log [▫$theta$▫/(1-▫$theta$▫)] versus log ▫$c_{inh}$▫ yielded straight lines with a slope change at the CMC. Accordingly, the CMC could be determined from these electrochemical measurements. The values of ▫$Delta$▫▫$G_{ads}$▫ calculated from the Langmuir plots are negative, suggesting that the inhibitive action of SDS in 0.5 M H2SO4 results from the electrostatic adsorption of C12H25SO4- ions onto the positively charged copper surface.
Ključne besede: electrochemistry, corrosion inhibitors, surfactants, potentiodynamic polarisation, corrosion kinetic parameters, copper, Langmuir isotherm, critical micelle concentration, sulphuric acid
Objavljeno: 01.06.2012; Ogledov: 803; Prenosov: 16
URL Celotno besedilo (0,00 KB)

Electrochemical impedance spectroscopy as a tool in the plate making process optimization
Tomislav Cigula, Regina Fuchs-Godec, Miroslav Gojo, Mojca Slemnik, 2012, izvirni znanstveni članek

Opis: The structure of the porous aluminium-oxide layer, which builds non-image areas, has the most significant influence on the quality of final graphical product. This paper presents the results of the application of EIS in the characterisation and detection of changes on the aluminium-oxide layer caused by chemical processing in highly alkaline solution. The Al2O3 layer was characterised using SEM, fractal dimension and surface free energy calculationand EIS analysis. The results of the investigation showed that chemical processing has a significant influence on the structure of aluminiumoxide which could lead to a decrease in the quality of the printing plate. EIS enables the detection of changes on the aluminium- oxide layer. Thetwo equivalent circuits are proposed. Based on modelling with the obtained EIS spectra, precise evaluation of developing time in which complete removal of the photoactive layer is achieved. This makes EIS a powerful tool in optimizing chemical processing of lithographic printing plates.
Ključne besede: printing plate, chemical processing, SEM, surface free energy, EIS
Objavljeno: 10.07.2015; Ogledov: 347; Prenosov: 28
.pdf Celotno besedilo (266,51 KB)

The inhibitive effect of vitamin-C on the corrosive performance of steel in HCl solutions
Milorad V. Tomić, Miomir Pavlović, Regina Fuchs-Godec, 2013, izvirni znanstveni članek

Ključne besede: vitamic C, corrosive performance, electrochemical results
Objavljeno: 10.07.2015; Ogledov: 243; Prenosov: 9
URL Celotno besedilo (0,00 KB)
Gradivo ima več datotek! Več...

Gregor Uhan, 2013, diplomsko delo

Opis: Namen diplomskega dela je določiti kritično micelno koncentracijo (CMC) za kationski surfaktant (trimetil-tetradecilamonijev klorid-TTSCl) in za neionski surfaktant Triton-X-100 pri standardnih pogojih in preučiti vpliv temperature na CMC. Kot topilo smo uporabili Milli-Q vodo. Pri tem smo se osredotočili na dve temperaturni območji. In sicer za kationski surfaktant je bilo območje od 288 K do 313 K, medtem ko za neionskega od 283 K do 313 K. Za vsakega posebej smo uporabili različni metodi: klasično konduktometrično metodo (kationski surfaktant) in metodo površinske napetosti (neionski surfaktant). S pomočjo le-teh smo za kationski surfaktant dobili odvisnost v obliki 'črke U' ter linearno padajočo odvisnost za neionski surfaktant, tako kot je v skladu z literaturo. Na koncu smo izračunali termodinamske količine: spremembo entalpije micelizacije (ΔH_mic^°), spremembo entropije micelizacije (ΔSmic) in spremembo Gibbsove energije (ΔG_mic^°). Pri tem smo vse tri količine za ionski surfaktant izračunali na dva različna načina in sicer v primeru, kjer se upošteva vpliv temperature na stopnjo disociacije protiiona (β) in kadar se ta vpliv lahko zanemari, če je sprememba β majhna. Za neionski surfaktant smo uporabili enačbe za izračun termodinamskih količin, pri čemu se stopnja disociacije proti-iona ne upošteva, saj neionski surfaktanti ne disociirajo. V obeh primerih smo ugotovili, da je proces micelizacije spontan saj je prosta Gibbsova energija micelizacije (ΔG_mic^°) negativna, medtem ko za ostali termodinamski količini lahko povemo, da sta bistveno drugačni, kar nam nakazujejo rezultati v tabelah.
Ključne besede: surfaktant, kritična micelna koncentracija (CMC), kationski surfaktant trimetil-tetradecilamonijev klorid (TTSCl), Neionski surfaktant (Triton-X-100), termodinamika micelizacije, agregacija, električna prevodnost, površinska napetost.
Objavljeno: 04.11.2013; Ogledov: 1774; Prenosov: 251
.pdf Celotno besedilo (2,50 MB)

Tanja Kondić, 2012, diplomsko delo

Opis: V diplomskem delu smo proučevali korozijsko obnašanje nerjavnega jekla PROKRON 1 v različnih koncentracijah HCl (c = 0,01; 0,1; 1,0 M HCl), ter ob različnih dodatkih inhibitorja (c = 0,0005; 0,001; 0,005; 0,01 M). Pri eksperimentalnem delu smo uporabili samo eno vrsto inhibitorja, in sicer vitamin C. Meritve so bile opravljene s potenciodinamsko polarizacijsko metodo, kjer smo primerjali inhibitorni učinek izbranega inhibitorja v prisotnosti različnih koncentracij vitamina C in HCl. V zaključnem delu meritev je bilo ugotovljeno, da se vitamin C obnaša z dvojnim delovanjem, saj ponekod deluje kot inhibitor, ponekod pa kot aktivator.
Ključne besede: nerjavno jeklo, korozija, inhibitor, vitamin C, klorovodikova kislina
Objavljeno: 16.10.2012; Ogledov: 1098; Prenosov: 165
.pdf Celotno besedilo (2,64 MB)

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