Electrosynthesis of hollow polypyrrole microtubes with a rectangular cross-section

We present results on the electrosynthesis of hollow rectangular microtubes of polypyrrole from neutral and alkaline solutions of salicylate. The electroactive films were prepared by electropolymerization of pyrrole on stainless steel substrate at a constant potential. The growth process of microtubes was studied by scanning electron microscopy (SEM). Deposition parameters such as salicylate concentration, monomer concentration, solution pH and electrode rotation have significant effects on the morphology of deposits. A plausible explanation for the occurrence of rectangular-sectioned microtubes is given.Fil: González, Belén. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería Química. Instituto de Ingeniería Electroquímica y Corrosión; ArgentinaFil: Saidman, Silvana Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería Química. Instituto de Ingeniería Electroquímica y Corrosión; Argentin

Low-Voltage Polarization in AOT Solution to Enhance the Corrosion Resistance of Nitinol

In this work, the corrosion behavior of bare nitinol (NiTi) alloy in Ringer's solution containing different concentrations of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) was first studied in order to determine whether the surfactant acts as a corrosion inhibitor. Results of potentiostatic and potentiodynamic experiments allowed concluding that AOT is a pitting corrosion inhibitor for NiTi. In a second stage of this research work, NiTi was treated under potentiostatic control (2.00 V) for 1 h in 0.10 M AOT solutions of pH 8.4 and 12. Static and rotating electrodes were used. The influence exerted by this treatment on the passive behavior of the alloy was studied in Ringer's solution using different electrochemical and surface analysis techniques. The best anticorrosion performance was obtained using a rotating electrode and AOT solution of pH 8.4. The thin oxide layer grown potentiostatically consists of TiO2, while no Ni was found in the outermost layer. The presence of this oxide layer allows reducing the amount of Ni and Ti released at open circuit potential conditions and at very positive potentials where pitting corrosion of the bare alloy occurs.Fil: Saugo, Melisa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería Química. Instituto de Ingeniería Electroquímica y Corrosión; ArgentinaFil: Flamini, Daniel Omar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería Química. Instituto de Ingeniería Electroquímica y Corrosión; ArgentinaFil: Saidman, Silvana Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería Química. Instituto de Ingeniería Electroquímica y Corrosión; Argentin

Corrosion resistance improvement of Ti-6Al-4V alloy by anodization in the presence of inhibitor ions

Colorful thin oxide films were synthesized by galvanostatic anodization on Ti-6Al-4V alloy. Three different aqueous solutions containing corrosion inorganic inhibitors (Na2MoO4, NaH2PO4 and NH4VO3) were employed for the anodization treatment. The effect of inhibitor anions on the corrosion behavior of the alloy in Ringer solution was studied. Open circuit potential (OCP), Tafel polarization, linear sweep voltammetry (LSV) and chronoamperometry (CA) were performed to evaluate the corrosion performance of the treated electrodes. The incorporation of the inhibitor ions was detected by the release of Mo, V and P through ICP-AES technique. The formed oxides were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results show that compact, amorphous oxides without pores or cracks were obtained independently of the solution used. The sample anodized in Na2MoO4 solution registered the lowest corrosion current density (0.11 μA/cm2), and it was able to protect the alloy even after 168 h of immersion in Ringer solution. No cracks or corrosion products were detected. The XPS analysis reveals the incorporation of molybdenum to the oxide film in the form of Mo6+ and Mo4+.Fil: Martínez, Alejandra Leonor. Universidad Nacional del Sur. Departamento de Ingeniería Química. Instituto de Ingeniería Electroquímica y Corrosión; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; ArgentinaFil: Flamini, Daniel Omar. Universidad Nacional del Sur. Departamento de Ingeniería Química. Instituto de Ingeniería Electroquímica y Corrosión; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; ArgentinaFil: Saidman, Silvana Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería Química. Instituto de Ingeniería Electroquímica y Corrosión; Argentin

Cerium Oxides for Corrosion Protection of AZ91D Mg Alloy

Die-cast AZ91D magnesium alloy (8.9 wt.% Al, 0.6 wt.% Zn, 0.2 wt.% Mn, and balance Mg), as novel alternative biodegradable material, has received great attention due to their potential use in biomedical implants. However, their poor corrosion resistance in physiological fluids restricts practical applications. Cerium-based coatings have been studied as an environmental friendly option to enhance the corrosion resistance of magnesium alloys. In order to control the biodegradation rate of AZ91D magnesium alloy in simulated physiological solution, the formation of a coating from a solution containing cerium nitrate (Ce(NO3)3) was studied. The effect of different additives in the treatment solution (ascorbic acid, citric acid, and sodium citrate) on the anticorrosive properties of the coatings was evaluated. The characterization of the coatings was done using electrochemical techniques and SEM/EDS, XRD, and XPS analyses. The corrosion properties were examined in Ringer solution by polarization studies, open circuit measurements, and faradaic impedance spectroscopy. Results showed that the incorporation of additives improves the anticorrosive properties of the Ce-based film. The coating modified with ascorbic acid provides the best corrosion resistance. According to XPS results, the film is mainly composed by Mg oxides or hydroxides and Ce oxides

Corrosion protection properties of polypyrrole coatings formed onto 316 L SS from a solution containing molybdate and salicylate

The electrosynthesis of PPy films onto 316L stainless steel fromnearly neutral and alkaline solutions containing molybdate and salicylate isreported. The corrosion behaviour of the coatings constituted by hollow rectangularmicrotubes was monitored in Ringer solution using open circuit potentialmeasurements, polarization techniques and electrochemical impedance spectroscopy.The polymer formed in a solution of pH 8 was the most efficient interms of corrosion protection. The coating significantly reduced the pitting corrosionof the substrate. The results were interpreted taking into considerationthe polymer electroactivity, the galvanic interaction polypyrrole/substrate andthe nature of dopants. Silver species were effectively immobilized onto the hollowrectangular-sectioned microtubes of PPy. The modified coatings demonstratedthat they have a good bactericidal activity against Escherichia coli andthey were also able to protect the substrate against corrosion in Ringer solution.Fil: Ramos, Camila. Universidad Nacional del Sur. Departamento de Ingeniería Química; ArgentinaFil: González, María Belén. Universidad Nacional del Sur. Departamento de Ingeniería Química; ArgentinaFil: Brugnoni, Lorena Inés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Ciencias Biológicas y Biomédicas del Sur. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Instituto de Ciencias Biológicas y Biomédicas del Sur; ArgentinaFil: Saidman, Silvana Beatriz. Universidad Nacional del Sur. Departamento de Ingeniería Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Electrochemical formation of polypyrrole films on Nitinol from sulfosuccinic acid solutions

En este trabajo se estudió la electrosíntesis de polipirrol (PPy) sobre Nitinol a partir de solucionesde ácidosulfosuccínico (0,25 M) y pirrol (0,25 M). El PPy fue formado potenciostáticamente ensoluciones de pH 1 y 7. Hasta donde tenemos conocimiento, es la primera vez que se realiza la electrodeposición de PPy en pre-sencia de ácido sulfosuccinico.La morfología de las películas se estudió mediante imágenes de microscopia de barrido electrónico, obser-vándose la típica forma globular del PPy. También se determinó, mediante energía dispersiva de rayos X (EDS), la presencia de S lo cualconfirma que el dopante fue incorporado a la matriz polimérica. Las películas formadas son muy adherentes y presentan una conductividad aceptable.Para poderevaluar el comportamiento ante la corrosión se realizaron diferentes experiencias electroquímicasen solución de Ringer: medición del potencial de circuito abierto, diagramas de Tafel yvoltametría de barri-do lineal. Si bien ambos recubrimientos mejoran la protección del sustrato, las películas formadas en solución de pH 1 ofrecen mejores resultados. El análisis de iones en soluciónmediante espectrometría de emisión atómica de plasma acoplado inductivo confirma que las películas son protectoras, evitando la liberación de iones Ni en la solución.In this work the electrosynthesis of polypyrrole (PPy) on Nitinol from solutionsof sulfosuccinic acid (0,25M) and pyrrole (0,25 M) was studied. The PPy was formed potentiostatically in solutions of pH 1 and 7. As far as we know, this is the first time that the electrodeposition of PPy is carried out in the presence of sul-fosuccinic acid.The morphology of the films was studied by scanning electron microscopy images, observing the typical globular shape of PPy. The presence of S was also determined by X-ray dispersive energy (EDX), confirming that the dopant was incorporated into the polymer matrix. The films formed are very adherent andexhibit acceptable conductivity.In order to evaluate the corrosion behaviour, different electrochemical experiments were performed in Ring-er's solution: measurement of open circuit potential, Tafel plotsand linear sweep voltammetry. While both coatings improve the protectionof the substrate, the films formed in pH 1 solution offer better results. The analysis of ions in solution by inductive coupled plasma atomic emission spectrometry confirms that the films are protective, preventing the release of Ni ions into the solution.Fil: Saugo, Melisa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería Química. Instituto de Ingeniería Electroquímica y Corrosión; ArgentinaFil: Flamini, Daniel Omar. Universidad Nacional del Sur. Departamento de Ingeniería Química. Instituto de Ingeniería Electroquímica y Corrosión; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; ArgentinaFil: Saidman, Silvana Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería Química. Instituto de Ingeniería Electroquímica y Corrosión; Argentin

Electroformation of coatings modified with silver on magnesium alloys for biomedical applications

Three different films modified with silver species were considered to enhance the corrosion resistance of AZ91D Mg alloy and to impart its surface with antibacterial activity. First, coatings were electrodeposited under potentiostatic conditions in electrolyte solutions containing Na2MoO4 and/or Ce(NO3)3 as main compounds, and H2O2, ascorbic acid or citric acid as additives. Incorporation of silver species was done by immersion of the samples in AgNO3 solutions. The obtained modified films were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The corrosion protection properties of the films were examined in a simulated physiological solution by open circuit measurements, linear polarization and electrochemical impedance spectroscopy (EIS). The antibacterial effect of the coatings was evaluated using Escherichia coli bacteria. Cerium and molybdenum-based coating modified with silver provides superior antibacterial and anticorrosive properties compared to the other films studied.Fil: Loperena, Ana Paula. Universidad Nacional del Sur. Departamento de Ingeniería Química. Instituto de Ingeniería Electroquímica y Corrosión; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Forero Lopez, Ana Deisy. Universidad Nacional del Sur. Departamento de Ingeniería Química. Instituto de Ingeniería Electroquímica y Corrosión; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Brugnoni, Lorena Inés. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Lehr, Ivana Leticia. Universidad Nacional del Sur. Departamento de Ingeniería Química. Instituto de Ingeniería Electroquímica y Corrosión; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Saidman, Silvana Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería Química. Instituto de Ingeniería Electroquímica y Corrosión; Argentin

Recubrimientos dobles de cerio y epoxi modificados con polipirrol y nanopartículas de plata formados sobre la aleación de Mg AZ91D

Due to their biocompatibility, biodegradability and mechanical characteristics similar to those of human bone, Mg alloys are a promising alternative as materials for the fabrication of temporary implants. However, its high rate of degradation in a physiological environment prevents their use in these applications. In order to increase the corrosion resistance of the Mg AZ91D alloy in a simulated physiological environment, double cerium and modified epoxy coatings were generated. As a first step, polypyrrole (PPy) modified with silver nanoparticles was chemically synthesized from pyrrole (Py), Ag-NO3 and Ce(SO4)2. Two sizes of nanoparticles were synthesized by varying the concentration of AgNO3 used for the synthesis of the powders. It was verified that the compounds have bactericidal properties against the Gram negative Escherichia coli (E. coli). From these results, a duplex coating was formed onto the AZ91D Mg alloy and then it was modified with the synthesized powders. The coating consisted of an inner cerium-based film and an epoxy film on top, 1 wt.% of the bactericidal composites was added to the resin before its application. Electrochemical analysis as anodic polarization, Tafel polarization curves, variation of the open circuit potential (OCP) and electrochemical impedance spec-troscopy (EIS) verified that the modified coatings were able to protect the alloy against corrosion in simulated physiological solution. The attained protection degree is attributed to the anticorrosive properties of both films and to the presence of polypyrrole (PPy) in the composite, which contributes to maintain the alloy in the passive state. At the same time, the addition of the composite confers antibacterial properties to the coating, which were evaluated through the Kirby-Bauer technique against bacteria E. coli.Fil: Loperena, Ana Paula. Universidad Nacional del Sur. Departamento de Ingeniería Química. Instituto de Ingeniería Electroquímica y Corrosión; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Lehr, Ivana Leticia. Universidad Nacional del Sur. Departamento de Ingeniería Química. Instituto de Ingeniería Electroquímica y Corrosión; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: González, María Belén. Universidad Nacional del Sur. Departamento de Ingeniería Química. Instituto de Ingeniería Electroquímica y Corrosión; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Brugnoni, Lorena Inés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Ciencias Biológicas y Biomédicas del Sur. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Instituto de Ciencias Biológicas y Biomédicas del Sur; ArgentinaFil: Saidman, Silvana Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería Química. Instituto de Ingeniería Electroquímica y Corrosión; Argentin

The potentiometric response of polypyrrole electrosynthesised in alkaline media

The study has been focused on the potentiometric response of polypyrrole films electrosynthesised in alkaline solutions onto vitreous carbon electrodes. The influence of different conditions for electropolymerisation and soaking on the potentiometric sensitivity of the film is analysed. A simple model allows to interpreting the ion sensitivity observed. The participation of OH - in the ion-exchange process is demonstrated, in agreement with previous results.Fil: Saidman, Silvana Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería Química. Instituto de Ingeniería Electroquímica y Corrosión; Argentin

Electrodeposition of bilayered polypyrrole on 316 L stainless steel for corrosion prevention

The electropolymerization of pyrrole in aqueous solutions of salicylate leads to the formation of hollow rectangular-sectioned microtubes. With the aim to develop a coating with this morphology but with better anticorrosive properties we synthesized a bilayer system by depositing a polypyrrole underlayer electropolymerized in the presence of molybdate and nitrate and a polypyrrole film formed by the microtubes as a top layer. The corrosion performance of the coatings was monitored by following the open circuit potentials, polarization curves and electrochemical impedance spectroscopy in acid and neutral chloride solutions. The bilayers have the capacity to protect the steel against uniform as well as against pitting corrosion during long exposure times. The system with the inner layer formed in alkaline solution was the most protective coating in this study. The results are discussed in terms of the galvanic interaction between the polymer and the substrate and the role played by the dopant anions.Fil: González, Belén. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería Química. Instituto de Ingeniería Electroquímica y Corrosión; ArgentinaFil: Saidman, Silvana Beatriz. Universidad Nacional del Sur. Departamento de Ingeniería Química. Instituto de Ingeniería Electroquímica y Corrosión; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentin