197,484 research outputs found
Aniline-based silane as a primer for corrosion inhibition of aluminium
No full textHybrid films based on polyaniline and polysiloxane moieties were successfully deposited on commercial aluminium alloy using N-(3- trimethoxysilylpropyl)aniline (AnSi) as primer. The spectroscopic studies conducted on both the silane solution and the resulting films, jointly with several corrosion tests in NaCl, strongly support the protection performance of the hybrid films. The overall study demonstrates that typical silane-based treatments with principally barrier action can gain in active properties if the silane compound contains monomers of conducting polymers as a functional group.Fil: Flamini, Daniel Omar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería; ArgentinaFil: Trueba, Mónica. Università degli Studi di Milano; ItaliaFil: Trasatti, Stefano P.. Università degli Studi di Milano; Itali
Quaternary glacial evolution in the Central Cantabrian Mountains (Northern Spain)
No full textPeer reviewe
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
EFFETTO DELLA SOLLECITAZIONE MECCANICA A FLESSIONE SUL COMPORTAMENTO A CORROSIONE DI LEGHE DI Al STRUTTURALI
No full textThe present work reports on the effect of constant bending load on the electrochemical behavior
of structural aluminum alloys AA 2024-T3 (Al-Cu-Mg) and AA 7075-T6 (Al-Zn-Mg-Cu). The single cycle anodic
polarization curves in 0.6 M NaCl (pH 6.5) were carried out using four-point bent beam specimens (4PBB).
Lower propensity to localized corrosion has been indicated for compressive stresses. The effect of tensile
stresses on the electrochemical response is more complex and depends on the alloy nature
Characterization and corrosion performance of poly(pyrrole-siloxane) films on commercial Al alloys
No full textAn alternative approach was developed for the surface treatment of as-received commercial aluminium alloys 6082-T6, 5083-H111 and 2024-T3 by using a pyrrole-based silane. One immersion step is sufficient for poly(pyrrole-siloxane) film deposition, with good adhesion and desirable morphological features. The combination in a single coating of polysiloxane linkages, acting as a barrier for aggressive species penetration towards the metal surface, and polypyrrole units manifesting active anodic protection, together with high degree of compactness, explains the significantly improved corrosion protection of the composite film in comparison to simple coatings of polymethylsiloxane and polypyrrole
Pyrrole-based silane primer for corrosion protection of commercial AA 2024 T3
No full textAn alternative approach was developed for surface treatment of as-received commercial AA 2024 T3 by using a pyrrole-based silane (SiPy). For film deposition, just one immersion step is enough, followed by curing. SiPy layer structure contains both polysiloxane bonds and pyrrole oligomers, with some degree of doping, giving a highly coherent layer. The superior film quality with respect to simple polysiloxane, is probably the main reason for the better corrosion performance obtained for SiPy on 2024
Electrochemical approach to repassivation kinetics of Al alloys : gaining insight into environmentally assisted cracking
No full textThis work provides a broad overview of the systematic experimental studies conducted in our group to understand the factors governing the transition to a more occluded corrosion front during the repassivation of Al alloys, manifested by the appearance of an inflection during anodic polarization into the active region in NaCl solutions. The collected data and the derived empirical relationships enabled us to discern the thermodynamic and kinetic aspects controlling the transition to more occluded local damage. From the thermodynamic standpoint, the potential at the inflection, namely, the pit transition potential Eptp, can be considered as the thermodynamic driving force of Al dissolution in the acidified pit-like solution in contact with a freshly created surface. The associated current density iptp and the steepness of the potential decrease with current below Eptp are determined by interfacial electrochemical kinetics. More importantly, all these properties are influenced by electrochemical and metallurgical events, including residual stresses. These findings point to the electrochemical approach in combination with external mechanical load as a promising tool for investigating environmentally assisted cracking, in particular, crack nucleation and non-steady crack tip processes
Study of Al alloy corrosion in neutral NaCl by the pitting scan technique
No full textThe corrosion behavior of commercial Al alloys was studied in neutral 0.6 mol L(-1) NaCl by using single-cycle polarization. Qualitative interpretation of pitting scans in both deaerated and naturally aerated NaCl solution, with the aid of corrosion morphology characterization, allowed for inference of the features of localized corrosion as a function of Al substrate nature. Electrochemical characteristic parameters such as pitting (E(pit)), repassivation or protection (E(prot)) potentials and pit transition potential (E(ptp)) were determined. The validity of the difference Delta E = vertical bar E(pit)-E(prot)vertical bar as criterion for susceptibility to localized corrosion of aluminium alloys is discussed
The repassivation response from single cycle anodic polarization : The case study of a sensitized Al-Mg alloy
No full textThe repassivation behaviour of artificially aged 5083-H111 Al-Mg alloy in near neutral NaCl solutions was investigated by means of single cycle anodic polarization. Artificial aging was carried out at 150 degrees C during different times up to 360 h. The characterization of the microstructure and composition by XRD, SEM/EDS and metallographic analyses pointed out most favoured grain-boundary beta(Al3Mg2) phase precipitation for 168 h of isothermal treatment time. Nitric acid mass loss test (NAMLT) and microhardness measurements indicated the highest degree of sensitization (DoS) and developed strength for 168 h as well. For all the aging conditions, the potential drop at high currents during the reverse scan of the cyclic polarization was detected at the pit transition potential E-ptp with similar but higher values than the corrosion potential of beta phase (E-corr approximate to -900 mV vs SCE). The associated current density i(ptp) and the steepness of the potential drop increase as the amount and contiguity of b phase precipitates along grain boundaries. The onset and sustenance of metastable conditions that limit the simultaneous repassivation of all the corroded surfaces are driven by the anodic dissolution of beta(Al3Mg2). Metastable processes that limit the hydration of metal ions while producing high local hydrogen concentration are more likely to involve the formation/decomposition of reactive hydride intermediates. E-ptp corresponds to the mixed electrode potential at which both metal dissolution and hydrogen evolution occur beyond some distance into the cavity, while iptp evaluates the catalytic activity of the corroding surfaces. The effective anodic charge transfer coefficient alpha(eff) determined from the steepness of the potential drop estimates the contribution of Cl- electromigration in response to local electrodissolution processes
Electrocatalytic activity for hydrogen evolution of polypyrrole films modified with noble metal particles
No full textPolypyrrole (Ppy) films of various thicknesses contg. particles of noble metals such as Pt, Ru and Ir were electrosynthesized on the surface of austenitic stainless steel (Ss). Two different approaches were applied: (i) electrodeposition of a polymer film from a soln. already contg. an anionic metal complex, followed by potentiodynamic or galvanostatic redn.; and (ii) presynthesized Ppy films modified by galvanostatic electrodeposition of noble metals from solns. of the metal complexes. Surface morphol. and compn. of the resulting layers were studied by means of SEM and XPS. The electrocatalytic activity of the modified electrodes for the hydrogen evolution reaction (her) was tested in 0.05 M H2SO4 by means of potentiodynamic techniques (0.5 mV s-1)
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