Líquidos iónicos con imidazolio como inhibidores de corrosión ácida para acero al carbono

En el presente trabajo se evaluaron las propiedades inhibidoras de dos líquidos iónicos: Cloruro de 1-metil-3-bencilimidazolio [Im+ Cl-] y acetato de 1-butil-3-bencilimidazolio [Im+ Ac-]. Los análisis electroquímicos de resistencia a la polarización lineal y polarización potenciodinámica sugirieron su comportamiento como inhibidores de corrosión tipo mixto, donde en presencia de éstos se disminuyó el ataque del medio de H₂SO₄ 1 M a la superficie metálica, siendo [Im+ Cl-] el más eficiente obteniendo 60% a 100 ppm. Este resultado fue soportado por el análisis DFT bajo el nivel de teoría B3LYP/6–311G++. Los análisis computacionales indican que [Im+ Cl-] presentó una preferencia a ser adsorbido en la superficie metálica a partir del anillo imidazolio e ion cloruro. El proceso de adsorción de ambos compuestos obedeció a la isoterma de Temkin, mediante adsorción tanto física como química.In the present work, the inhibitory properties of two ionic liquids were evaluated: 1-methyl-3-benzylimidazolium chloride [Im+ Cl-] and 1-butyl-3-benzylimidazolium acetate [Im+ Ac-]. The electrochemical analyzes of resistance to linear polarization and potentiodynamic polarization suggested their behavior as mixed-type corrosion inhibitors, where in their presence the attack of the 1 M H₂SO₄ medium on the metal surface decreased, being with [Im+ Cl-] the most efficient obtaining 60% at 100 ppm. This result was supported by DFT analysis under the B3LYP/6–311G++ level of theory. Computational analyzes indicate that [Im+ Cl-] presented a preference to be adsorbed on the metal surface from the imidazolium ring and chloride ion. The adsorption process of both compounds obeyed the Temkin isotherm, through both physical and chemical adsorption

Propiedades inhibidoras de líquidos iónicos a base de yoduro para acero API 5L X52 en medio ácido

En el presente trabajo se analizaron las propiedades inhibidoras de dos LIs, yoduro de 1,2-dimetil-3-propil-imidazolio [3Im+I-] y yoduro de 1,2-dimetil-3-butil-imidazolio [4Im+I-] en HCl 1.0 M para el acero API 5L X52 mediante técnicas electroquímicas de resistencia a la polarización (Rp) y polarización potenciodinámica (PDP), isotermas de adsorción y análisis computacional (DFT). Se determinó que el comportamiento inhibidor fue en el siguiente orden: [4Im+I-]>[3Im+I-], esto atribuido a la mayor longitud de cadena alquílica. Se observó la dependencia de la eficiencia de inhibición (EI) en función de la concentración del LI. Mediante Rp y PDP se sugiere la formación de una película inhibidora mediante procesos de adsorción que bloquean los sitios activos de la superficie y disminuyen el daño. Por otro lado, DFT sugiere que tanto el yoduro como el nitrógeno del imidazolio actúan sitios reactivos que interactúan con la superficie metálica.In the present work, the inhibitory properties of two LIs, 1,2-dimethyl-3-propyl-imidazolium iodide [3Im+I-] and 1,2-dimethyl-3-butyl-imidazolium iodide [4Im+I-] were analyzed in 1.0 M HCl for API 5L X52 steel using electrochemical techniques of resistance to polarization (Rp) and potentiodynamic polarization (PDP), adsorption isotherms and computational analysis (DFT). It will be produced that the inhibitory behavior was in the following order: [4Im+I-]>[3Im+I-], this attributed to the greater length of the alkyl chain. The dependence of the inhibition efficiency (EI) as a function of the concentration of the LI was exhausted. Rp and PDP suggest the formation of an inhibitory film through adsorption processes that block the active sites on the surface and reduce damage. On the other hand, DFT suggests that both the iodide and the imidazolium nitrogen act as reactive sites that interact with the metal surface

Estudio químico y electroquímico de compuestos derivados de amonio cuaternario como inhibidores de corrosión del acero en ácido clorhídrico

Tesis (Doctorado en Ciencias en Metalurgia y Materiales), Instituto Politécnico Nacional, SEPI, ESIQIE, 2016, 1 archivo PDF, (108 páginas). tesis.ipn.m

Synthesis of Ammonium-Based ILs with Different Lengths of Aliphatic Chains and Organic Halogen-Free Anions as Corrosion Inhibitors of API X52 Steel

In the present work, synthesis and characterization of 15 ionic liquids (ILs) derived from quaternary ammonium and carboxylates were carried out in order to proceed to their evaluation as corrosion inhibitors (CIs) of API X52 steel in 0.5 M HCl. Potentiodynamic tests confirmed the inhibition efficiency (IE) as a function of the chemical configuration of the anion and cation. It was observed that the presence of two carboxylic groups in long linear aliphatic chains reduced the IE, whereas in shorter chains it was increased. Tafel-polarization results revealed the ILs as mixed-type CIs and that the IE was directly proportional to the CI concentration. The compounds with the best IE were 2-amine-benzoate of N,N,N-trimethyl-hexadecan-1-ammonium ([THDA+][−AA]), 3-carboxybut-3-enoate of N,N,N-trimethyl-hexadecan-1-ammonium ([THDA+][−AI]), and dodecanoate of N,N,N-trimethyl-hexadecan-1-ammonium ([THDA+][−AD]) within the 56–84% interval. Furthermore, it was found that the ILs obeyed the Langmuir adsorption isotherm model and inhibited the corrosion of steel through a physicochemical process. Finally, the surface analysis by scanning electron microscopy (SEM) confirmed less steel damage in the presence of CI due to the inhibitor–metal interaction

Corrosion resistance of the dissimilar alloy AL6XN-Inconel 718 in 0.5 M NaCl

In the present work, the corrosion resistance of the dissimilar alloy AL6XN-Inconel 718 bound by the Gas Tungsten Arc Welding (GTAW) method was studied. Different alloy zones were analyzed: base materials (BMs), heat affected zones (HAZs) and welds. The effect exerted by the GTAW method on the corrosion resistance displayed by such dissimilar alloy in 0.5 M NaCl was established by means of corrosion studies employing potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) tests. The electrochemical results revealed that the alloy HAZs are more susceptible to corrosion due to microstructure changes caused mainly by elements such as Ni, Cr and Mo during the GTAW process

The Inhibition of Aluminum Corrosion in Sulfuric Acid by Poly(1-vinyl-3-alkyl-imidazolium Hexafluorophosphate)

Compounds of poly(ionic liquid)s (PILs), derived from imidazole with different alkylic chain lengths located in the third position of the imidazolium ring (poly(1-vinyl-3-dodecyl-imidazolium) (PImC12), poly(1-vinyl-3-octylimidazolium) (PImC8) and poly(1-vinyl-3-butylimidazolium) (PImC4) hexafluorophosphate) were synthesized. These compounds were tested as corrosion inhibitors on aluminum alloy AA6061 in diluted sulfuric acid (0.1–1 M H2SO4) by weight loss tests, polarization resistance measurements and inductively coupled plasma optical emission spectroscopy. Langmuir’s isotherms suggested film formation on bare alloy while standard free energy indicated inhibition by a physisorption process. However, compound efficiencies as inhibitors ranked low (PImC12 > PImC8 > PImC4) to reach 61% for PImC12 in highly diluted acidic solution. Apparently, the high mobility of sulfates favored their adsorption in comparison to PILs. The surface film displayed general corrosion, and pitting occurred as a consequence of PILs’ partial inhibition along with a continuous dissolution of defective patchy film on formation. A slight improvement in efficiency was displayed by compounds having high molecular weight and a long alkyl chain, as a consequence of steric hindrance and PIL interactions

The Inhibition of Aluminum Corrosion in Sulfuric Acid by Poly(1-vinyl-3-alkyl-imidazolium Hexafluorophosphate)

Compounds of poly(ionic liquid)s (PILs), derived from imidazole with different alkylic chain lengths located in the third position of the imidazolium ring (poly(1-vinyl-3-dodecyl-imidazolium) (PImC12), poly(1-vinyl-3-octylimidazolium) (PImC8) and poly(1-vinyl-3-butylimidazolium) (PImC4) hexafluorophosphate) were synthesized. These compounds were tested as corrosion inhibitors on aluminum alloy AA6061 in diluted sulfuric acid (0.1–1 M H2SO4) by weight loss tests, polarization resistance measurements and inductively coupled plasma optical emission spectroscopy. Langmuir’s isotherms suggested film formation on bare alloy while standard free energy indicated inhibition by a physisorption process. However, compound efficiencies as inhibitors ranked low (PImC12 > PImC8 > PImC4) to reach 61% for PImC12 in highly diluted acidic solution. Apparently, the high mobility of sulfates favored their adsorption in comparison to PILs. The surface film displayed general corrosion, and pitting occurred as a consequence of PILs’ partial inhibition along with a continuous dissolution of defective patchy film on formation. A slight improvement in efficiency was displayed by compounds having high molecular weight and a long alkyl chain, as a consequence of steric hindrance and PIL interactions