Hybrid sol-gel coatings containing clay nanoparticles for corrosion protection of mild steel

The development of a new environment-friendly anticorrosive coating for mild steel substrate is afforded in this work. The combined use of cerium, as a self-healing agent, and clay nanoparticles, as improvers of the barrier properties, was considered to the development of new anticorrosive sol-gel coatings. Nanostructured hybrid films were synthesized by the sol-gel route from tetraethoxysilane (TEOS) and 3-glicidoxipropyl-trimetoxisilano (GPTMS) using laminar nanoclays (Laponite Na+0.7[Si8Mg5.5Li0.3H4O24]−0.7) to improve mechanical and barrier properties, and Ce(NO3)3?6H2O as a supplier of Ce(III) to provide an inhibiting effect in the event of coating failure. Carbon steel plates, AISI 1010, were used as substrates. Prior to the application of the coating, samples were treated with a phosphoric acid 2% v/v in order to improve coating adherence.In order to evaluate cerium effect, electrochemical behaviour of films containing Laponite and cerium salts (TGL-Ce) were compared with films containing only Laponite (TGL) by means of potentiodynamic polarization tests and electrochemical impedance spectroscopy (EIS) measurements using a 0.35 wt% NaCl solution. Microstructural characterization and surface analysis of substrates and sol-gel coatings were performed by optical microscopy and by XPS techniques. The use of nanoclays allowed to achieve a significant improvement of the anticorrosive behaviour of the cerium doped coating at the same time that enhances the physical integrity of the coatings under immersion tests.Fil: Santana, Ianina Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Pepe, Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Schreiner, Wido H.. Universidade Federal do Paraná; BrasilFil: Pellice, Sergio Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Ceré, Silvia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin

Synthesis and Structure-Activity Relationship of a WO 3

In this study we prepared a WO3-based catalyst to investigate its catalytic activity in the total oxidation of the volatile organic compounds known as benzene, toluene and xylene (BTX). For a range of low temperatures (50-450ºC) the only reaction products were CO2 and H2O. The results for the catalyst characterization suggested that the high catalytic activity could be attributed to the effects of a strong metal interaction, which is possibly originated from the small lattice parameter difference between the (111), (020) and (002) lattice planes and the presence of W4+, W5+ and W6+ species on the surface of the catalyst which react with active oxygen species

Protective hybrid sol-gel coatings containing bioactive particles on surgical grade stainless steel: Surface characterization

Metallic materials are the most used materials as orthopaedic or dental implants for their excellent mechanical properties. However, they are not able to create a natural bonding with the mineralized bone and they could release metallic particles that could finally end in the removal of the implant. One way to avoid these effects is to protect the metallic implant with a biocompatible coating. In this work there are analyzed two kinds of protective organic-inorganic sol-gel made coatings with the adding of glass-ceramic particles with the aim of generating bioactivity. The samples are surface characterized by SEM, XRD and XPS. Amorphous hydroxyapatite (aHAp) deposited on the samples after 30 days of immersion in simulated body fluid (SBF) is detected on the samples and its presence is considered as a first signal of bioactivity. © 2007 Elsevier B.V. All rights reserved.Fil: Ballarre, Josefina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: López, Damián. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Schreiner, Wido H.. Universidade Federal do Paraná; BrasilFil: Duran, Alicia. Instituto de Ceramica y Vidrio de Madrid; EspañaFil: Ceré, Silvia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin

Surface modification of titanium by anodic oxidation in phosphoric acid at low potentials. Part 1. Structure, electronic properties and thickness of the anodic films

Titanium surface characteristics determine the degree of success of permanent implants. The topography, morphology of the surface in micro and nano scales, the impurities present and other characteristics are a main concern, and therefore a multi-technique approach is required in order to evaluate modification process effects on the surface. Surface modification of titanium in the nanometrical range was performed by means of anodisation in phosphoric with the aim of improving both the biocompatibility and the corrosion resistance in the biological media. Biocompatible characteristics of the modified titanium surface, as the presence of anatase in the oxide film and the incorporation of phosphate to the surface, were determined. Moreover, the electronic properties of the surface oxide presented a carrier number adequate for biomedical applications. The increase in the film thickness from 3 to 42 nm was estimated from EIS results when anodising potentials from 0 to 30 V were applied, whereas a bi-layer structure of the protective oxides formed was determined.Fil: Gomez Sanchez, Andrea Valeria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Schreiner, Wido H.. Universidade Federal do Paraná; BrasilFil: Duffó, Gustavo Sergio. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Unidad de Actividad de Materiales (CAC); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Martín; ArgentinaFil: Ceré, Silvia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin

Nitrite corrosion inhibition in chloride-rich electrolytes correlated to the electrical properties of surface films on carbon steel

The electronic properties and the composition of surface films grown in pore simulating solutions are studied using various electrochemical and surface techniques and then correlated to the inhibiting efficiency of nitrite ions in chloride-rich alkaline solutions. In nitrite-free and chloride-rich solutions, the external layer of the surface film is porous, defective and rich in Fe(III). Instead, when nitrite and chloride ions are simultaneously present, the Fe(II) content increases and the film becomes thicker, ordered and more protective. In the absence of nitrite ions, chloride ions induce high donor densities that correlate to a high susceptibility to localized corrosion. In contrast, the donor density decreases noticeably when nitrites and chlorides are both present and also increases with ageing time, reaching values comparable to those calculated for uncontaminated solutions.Fil: Frontini, María Alejandra. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; ArgentinaFil: Schreiner, Wido H.. Universidade Federal do Paraná; BrasilFil: Vazquez, Marcela Vivian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Valcarce, María Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin

Phosphate ions as effective inhibitors for carbon steel in carbonated solutions contaminated with chloride ions

This investigation focuses on sodium biphosphate (Na2HPO4) as corrosion inhibitor for construction steel. All the tests are carried out in a solution that simulates the composition of the pores in chloride-contaminated carbonated concrete. The carbonated solution (CS) contained Na2CO3 (0.0015 mol L-1), NaHCO3 (0.03 mol L-1) and NaCl (0.1 mol L-1), resulting in [Cl-]/[OH-]=10000. Inhibited solutions (IS20, IS60 and IS100) incorporated 20, 60, and 100 mmol L-1 Na2HPO4 respectively. These were labeled IS20, IS60 and IS100 respectively and result in [HPO42-]/[Cl-] = 0.2, 0.6, and 1. Cyclic voltammograms and anodic polarization curves were complemented with micro-Raman spectroscopy and XPS, to evaluate the surface film composition. The results show that chloride contamination promotes active corrosion. When phosphate ions are incorporated, steel becomes passive with a more positive corrosion potential (Ecorr), and pitting presents as the predominant form of localized corrosion. Raman spectra show a broad band, centred in 982 cm-1, suggesting that phosphates incorporate to the passive film. Phosphates are also present in the corrosion products. The surface film becomes more protective to pitting for the highest biphosphate content. However, after pitting no repassivation was detected. After over one month in immersion, steel remains passive in the condition IS100, with inhibition efficiency higher than 99%. In contrast, in the case of IS60 and IS20, pitting was detected.It can be concluded that phosphate ions are good candidates to be used as corrosion inhibitors for steel in chloride-contaminated concrete.Fil: Yohai del Cerro, Lucía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Schreiner, Wido H.. Universidade Federal do Paraná; BrasilFil: Vazquez, Marcela Vivian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Valcarce, María Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin

Inhibiting steel corrosion in simulated concrete with low phosphate to chloride ratios

Phosphate ions are studied as corrosion inhibitors in pore simulating solutions highly contaminated with chloride ions. The investigation aims at understanding the role of phosphates in the corrosion inhibition mechanism, employing potentiodynamic polarization tests, micro-Raman spectroscopy, impedance spectroscopy, X-ray photo electronic spectroscopy (XPS) and weight loss tests. Two inhibitor/chloride ratios were assessed, [PO43−]/[Cl−] = 0.2 and 0.6. When [PO43−]/[Cl−] = 0.6, pitting is inhibited, even after 90 days exposure. [PO43−]/[Cl−] = 0.2 only delayed the onset of localized attack. XPS showed that phosphates incorporate to the surface film. Phosphate ions behaved as mixed-type corrosion inhibitors. The results are interpreted by the participation of phosphates in the duplex passive film being formed on carbon steel.Fil: Yohai del Cerro, Lucía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Schreiner, Wido H.. Universidade Federal do Paraná; BrasilFil: Valcarce, María Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Vazquez, Marcela Vivian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin

Magnesium alloys implants coated with 58S sol gel bioactive glass to retard first stage corrosion

Two composition of 58S (60 mol% SiO2, 36 mol% CaO, 4 mol% P2O5) glass coatings were made by sol gel and applied by dip coating onto two commercial magnesium alloys (AZ31 and AZ91) as a strategy to retard the hydrogen evolution and accelerate the deposition of a hydroxyapatite layer to enhance bioactivity. Surface studies with XPS, Raman spectroscopy and SEM techniques are presented after coating deposition and after immersion in Hanks´ Balance Salt Solution (HBSS) at 37 C. Electrochemical tests were also conducted to evaluate the evolution of the coating with immersion. It is observed that even the coating present defects, it is able to retard substrate degradation and this effect is more pronounced for AZ91 as substrate. Coating performance is mainly governed by the substrate due the defective nature of the film.Fil: Omar, Sheila Ayelén. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Castro, Yolanda. Instituto de Ceramica y Vidrio de Madrid; EspañaFil: Ballarre, Josefina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Schreiner, Wido H.. Universidade Federal do Paraná; BrasilFil: Duran, Alicia. Instituto de Ceramica y Vidrio de Madrid; EspañaFil: Ceré, Silvia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin