Tullio Monetta | Università degli Studi di Napoli "Federico II" (original) (raw)

Papers by Tullio Monetta

La corrosione dell'acciaio nel calcestruzzo è un problema strutturale che colpisce le struttu... more La corrosione dell'acciaio nel calcestruzzo è un problema strutturale che colpisce le struttu-re in cemento armato. Il processo di corrosione, a causa dell'espansione volumetrica degli ossidi dell’acciaio, porta alla fessurazione del copriferro. Le principali conseguenze sono la riduzione della sezione di acciaio e dell’aderenza che comportano perdita di capacità por-tante. Al fine di valutare la perdita di tale capacità dovuta alla corrosione, sono stati studiati metodi teorici e/o sperimentali volti a indagare la perdita di sezione dell’acciaio, la riduzione del momento flettente e la perdita di aderenza. I risultati ottenuti sono importanti strumenti al fine di determinare lo stato di conservazione delle strutture, spesso concausa di crolli e dissesti.

ABSTRACT We demonstrate that is possible to create a uniform distribution of TiO2 nanotubes array... more ABSTRACT We demonstrate that is possible to create a uniform distribution of TiO2 nanotubes array on complex geometry samples, like a titanium screw commonly used as a dental implant, using a very simple experimental set-up. TiO2 nanotubes array were synthesized by a potentiostatic anodization process, in H3PO4 and HF aqueous solution. During the anodization, the titanium implants were used as working electrode and platinum sheet as a counter electrode, in order to anodize the whole screw, a rotating device was used. The morphology of the porous layers is controlled by anodization potential, electrolyte composition, anodization duration and cell temperature as well as by the geometry of the samples. This finding opens new perspectives in testing medical devices to all researchers. Scientists will may able to use the “real” prosthesis, exactly the same that are used in clinical practice, coating them with nanotubes. It will be easier to analyse the devices response using samples formed by “real” prosthesis, which could be tested in living bodies.

Aerospace, 2015

Recently, the use of graphene as a conductive nanofiller in the preparation of inorganic/polymer ... more Recently, the use of graphene as a conductive nanofiller in the preparation of inorganic/polymer nanocomposites has attracted increasing interest in the aerospace field. The reason for this is the possibility of overcoming problems strictly connected to the aircraft structures, such as electrical conductivity and thus lightning strike protection. In addition, graphene is an ideal candidate to enhance the anti-corrosion properties of the resin, since it absorbs most of the light and provides hydrophobicity for repelling water. An important aspect of these multifunctional materials is that all these improvements can be realized even at very low filler loadings in the polymer matrix. In this work, graphene nanoflakes were incorporated into a water-based epoxy resin, and then the hybrid coating was applied to Al 2024-T3 samples. The addition of graphene considerably improved some physical properties of the hybrid coating as demonstrated by Electrochemical Impedance Spectroscopy (EIS) analysis, ameliorating anti-corrosion performances of raw material. DSC measurements and Cross-cut Test showed that graphene did not affect the curing process or the adhesion properties. Moreover, an increment of water contact angle was displayed.

Corrosion Reviews, 2015

ABSTRACT Electrochemical noise measurement and analysis enable one to obtain information on corro... more ABSTRACT Electrochemical noise measurement and analysis enable one to obtain information on corroding systems without applying any potential or current perturbation to the corroding surface, and they are thereby nondestructive techniques, suitable for corrosion monitoring. The measurement process requires converting the analog potential or current signal in a digital dataset that can be used to perform mathematical operations with a variety of approaches. The analog-to-digital conversion is a critical step since, after the conversion has been performed, it is impossible to correct for artefacts that occurred during the conversion. Additionally, the electrochemical noise generated during corrosion is generally overlapped to the instrumental noise and to the electrical interference that are present in the environment where the measurement is performed. In this work, the process of analog-to-digital conversion of electrochemical noise signals is analyzed in detail by simulating the conversion of a representative simulated noise signal. With this approach, the possible issues arising from the analog-to-digital conversion process are highlighted and the key features arising from instrumental noise, aliasing, and electrical interference are identified.

Electrochimica Acta, 2015

The corrosion behaviour of magnesium in chloride-containing aqueous environment was investigated ... more The corrosion behaviour of magnesium in chloride-containing aqueous environment was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) performed simultaneously with real-time hydrogen evolution measurements and optical imaging of the corroding surface. The potentiodynamic investigation revealed substantial deviations from linearity in close proximity of the corrosion potential. In particular, differences in the slope of the current/potential curves were observed for small polarizations above or below the corrosion potential. These observations, suggest that the usual method based on the use of the Stern-Geary equation to convert a value of resistance into a value of corrosion current is inadequate. Nonetheless, a very good correlation between values of resistances estimated by EIS and corrosion currents obtained from real-time hydrogen measurement was found. Real-time hydrogen measurement also enabled, for the first time, direct measurement of an 'apparent' Stern-Geary coefficient for magnesium. In order to rationalize the complex behaviours experimentally observed, an electrical model for the corroding magnesium surface is presented.

Journal of The Electrochemical Society

Surface and Interface Analysis, 2013

ABSTRACT Due to risk connected to the chromium use, several companies try to find ‘true’ chromium... more ABSTRACT Due to risk connected to the chromium use, several companies try to find ‘true’ chromium free products to treat aluminum surfaces. Aim of this work was to evaluate and test some treatment systems for avionics applications, in order to replace standard chromate processes based on CrVI. AA2014-T3 and AA6082-T6 aluminum alloys were subjected to conversion coating processes based on lithium or zirconium salts. Results were compared to those obtained using commercial chromium free products. The electrochemical and corrosion behavior was investigated using the d.c. electrochemical technique and salt spray test (SST). Moreover, in order to be used in some aircraft and aerospace devices, low electrical contact resistance (ECR) is required; these tests were carried out according to a military standard. The results demonstrated that the AA6082-T6 alloy, treated using lithium salts, has passed the SST but did not pass the ECR test. AA2014-T3 alloy treated using lithium salts has passed neither the SST nor the low electrical resistance test. Copyright © 2013 John Wiley & Sons, Ltd.