Ellagic Acid as Green Corrosion Inhibitor: a Necessary Validation

Corrosion of metals is an unavoidable but controllable process. Among techniques developed to slow down or prevent metal deterioration the addition of small amount of inhibitors directly in the corrosive environment is a quite common strategy. In particular, among organic compounds effectively used as adsorption inhibitors (thanks to N, O and/or S atoms that act as anchoring groups for metal surface) only a few percentage belongs to the so called \u201cgreen inhibitor\u201d class. In this field most of the studies employ plant extracts being rich in phytochemical constituents considered to be potential eco-friendly corrosion inhibitors. However, the often extraordinary complexity of crude extracts makes difficult the rationalization of the inhibition mechanism. So, from a purely academic point of view, the study of pure compounds is often encouraged. Among potential green inhibitors our attention has been focused on ellagic acid (EA) that can be obtained by hydrolysis of ellagitannin contained in peels of pomegranate. Ellagic acid is a polyphenol having four phenolic and two lactone groups that should act like two and one couples of equivalent sites, respectively, due to the C2h molecular symmetry. Up to know the corrosion inhibition properties of EA was only marginally studied in literature, both theoretically and experimentally. However some reported results need to be validated because of discrepancies concerning some fundamental chemical physical features of the target acid, like i) solubility in pure water (9 mg/dm3 versus 1.2 g/dm3) and ii) pKa values for the two acid dissociation processes. For this purposes, using UV-Vis absorption spectroscopy, a mainly-aqueous medium was selected to assure homogeneity of the EA-based solution; after that the corrosion inhibition properties of ellagic acid toward mild steel was studied by weight loss measurements (according to ASTM G1 standard practice) and by electrochemical tests. Preliminary results performed in 1% v/v MeOH/H2O mixture with HCl 0.05 M point to potentially interesting inhibition effect even working with 1.0 1910\u20135 M EA (i.e., 3 mg/dm3)

Green Corrosion Inhibitors from Natural Sources and Biomass Wastes

Over the past decade, green chemistry has been emphasizing the importance of protecting the environment and human health in an economically beneficial manner aiming at avoiding toxins and reducing wastes. The field of metallic materials degradation, generally faced by using toxic compounds, found a fertile research field in green chemistry. In fact, the use of inhibitors is a well-known strategy when metal corrosion needs to be prevented, controlled, or retarded. Green inhibitors are biodegradable, ecologically acceptable and renewable. Their valorization expands possible applications in industrial fields other than \u2018waste to energy\u2019 in the perspective of circular economy. Although lot of experimental work has been done and many research papers have been published, the topic of green inhibitors is still an open issue. The great interest in the field expanded the research, resulting in high numbers of tested molecules. However, the most frequently adopted approaches are conventional and, hence, not suitable to fully characterize the potential efficacy of inhibitors. All the mentioned aspects are the object of the present review and are meant as a constructive criticism to highlight the weak points of the green inhibitors field as to re-evaluate the literature and address the future research in the field that still lacks rationalization

Valutazione del comportamento a corrosione di differenti trattamenti termochimici su substrati in acciaio

Lo scopo del presente lavoro è stato quello di porre le basi per la messa a punto di un protocollo di provache permetta di differenziare i diversi trattamenti superficiali in termini di resistenza a corrosione.A tal fine, tre diversi substrati in acciaio, convenzionalmente impiegati nelle specifiche applicazioni(42CrMo4, ST52 e C45) sono stati sottoposti a differenti trattamenti termochimici quali nitrurazione enitrocarburazione ionica, seguiti da post-ossidazione in protossido di azoto, e a nitrocarburazione salina

Measuring individual overpotentials in an operating solid-oxide electrochemical cell

We use photo-electrons as a non-contact probe to measure local electrical potentials in a solid-oxide electrochemical cell. We characterize the cell in operando at near-ambient pressure using spatially-resolved X-ray photoemission spectroscopy. The overpotentials at the interfaces between the Ni and Pt electrodes and the yttria-stabilized zirconia (YSZ) electrolyte are directly measured. The method is validated using electrochemical impedance spectroscopy. Using the overpotentials, which characterize the cell's inefficiencies, we compare without ambiguity the electro-catalytic efficiencies of Ni and Pt, finding that on Ni H_2O splitting proceeds more rapidly than H2 oxidation, while on Pt, H2 oxidation proceeds more rapidly than H2O splitting.Comment: corrected; Phys. Chem. Chem. Phys., 201

Scanning tunneling microscopy of deoxyribonucleic acid during replication

Scanning tunneling microscopy was used to produce topographic images of uncoated and unlabeled deoxyribonucleic acid (DNA) in air, on a graphite substrate. The images show for the first time a DNA molecule that had been isolated while it was replicating

The radio relic in Abell 2256: overall spectrum and implications for electron acceleration

The galaxy cluster Abell 2256 hosts one of the most intriguing examples in the class of radio relics. It has been found that this radio relic has a rather flat integrated spectrum at low frequencies that would imply an injection spectral index for the electrons that is inconsistent with the flattest allowed by the test particle diffusive shock acceleration (DSA). We performed new high-frequency observations at 2273, 2640, and 4850 MHz. Combining these new observations with images available in the literature, we constrain the radio integrated spectrum of the radio relic in Abell 2256 over the widest sampled frequency range collected so far for this class of objects (63 -10450 MHz). Moreover, we used X-ray observations of the cluster to check the temperature structure in the regions around the radio relic. We find that the relic keeps an unusually flat behavior up to high frequencies. Although the relic integrated spectrum between 63 and 10450 MHz is not inconsistent with a single power law with $\alpha_{63}^{10450}= 0.92\pm 0.02$, we find hints of a steepening at frequencies > 1400 MHz. The two frequency ranges 63-1369 MHz and 1369-10450 MHz are, indeed, best represented by two different power laws, with $\alpha_{63}^{1369}= 0.85\pm 0.01$ and $\alpha_{1369}^{10450}= 1.00\pm 0.02$. This broken power law would require special conditions to be explained in terms of test-particle DSA, e.g., non-stationarity of the spectrum and/or non-stationarity of the shock. On the other hand, the single power law would make of this relic the one with the flattest integrated spectrum known so far, even flatter than what allowed in the test-particle approach to DSA. We find a rather low temperature ratio of $T_2/T_1 \sim 1.7$ across the G region of the radio relic and no temperature jump across the H region.Comment: 18 pages, 11 figures, 9 tables. Accepted for publication in Astronomy & Astrophysic

Corrosion behavior and surface properties of PVD coatings for mold technology applications

Chrome plating is still one of the best solutions to coat martensitic steel used in the molding of plastics and rubbers. However, current stringent regulations on environmental impact call for more sustainable processes. In the present work, some physical vapor deposition (PVD) nitride coatings were produced on X155CrMoV12 steel and characterized in terms of both corrosion behavior and surface properties. Results indicated that titanium-based PVD coatings could be a valuable alternative to chromium-based coatings as they exhibited a good compromise between corrosion and surface properties. AlTiN and TiN PVD coatings exhibited adequate hardness for plastic mold applications, with AlTiN reaching hardness as high as 2000 HV. Moreover, the critical loads and adhesion properties were found to be definitely better than those of chromium-based coatings. From a corrosion point of view, the presence of multilayers in AlTiN did not seem to be beneficial as the breakdown potential for TiN (single layer) was ca. 1.1 V vs. saturated calomel electrode (SCE) compared to 0.85 V vs. SCE for AlTiN in aggressive media (NaCl)

Atomically dispersed Pt-N-4 sites as efficient and selective electrocatalysts for the chlorine evolution reaction

Chlorine evolution reaction (CER) is a critical anode reaction in chlor-alkali electrolysis. Although precious metal-based mixed metal oxides (MMOs) have been widely used as CER catalysts, they suffer from the concomitant generation of oxygen during the CER. Herein, we demonstrate that atomically dispersed Pt-N-4 sites doped on a carbon nanotube (Pt-1/CNT) can catalyse the CER with excellent activity and selectivity. The Pt-1/CNT catalyst shows superior CER activity to a Pt nanoparticle-based catalyst and a commercial Ru/Ir-based MMO catalyst. Notably, Pt-1/CNT exhibits near 100% CER selectivity even in acidic media, with low Cl- concentrations (0.1M), as well as in neutral media, whereas the MMO catalyst shows substantially lower CER selectivity. In situ electrochemical X-ray absorption spectroscopy reveals the direct adsorption of Cl- on Pt-N-4 sites during the CER. Density functional theory calculations suggest the PtN4C12 site as the most plausible active site structure for the CER

Coseismic deformation and source modeling of the May 2012 Emilia (Northern Italy) earthquakes

On May 20th, 2012, an ML 5.9 earthquake (Table 1) occurred near the town of Finale Emilia, in the Central Po Plain, Northern Italy (Figure 1). The mainshock caused 7 casualties and the collapse of several historical buildings and industrial sheds. The earthquake sequence continued with diminishing aftershock magnitudes until May 29th, when an ML 5.8 earthquake occurred near the town of Mirandola, ~12 km WSW of the mainshock (Scognamiglio et al., 2012). This second mainshock started a new aftershock sequence in this area, and increased structural damage and collapses, causing 19 more casualties and increasing to 15.000 the number of evacuees. Shortly after the first mainshock, the Department of Civil Protection (DPC) activated the Italian Space Agency (ASI), which provided post-seismic SAR Interferometry data coverage with all 4 COSMO-SkyMed SAR satellites. Within the next two weeks, several SAR Interferometry (InSAR) image pairs were processed by the INGV-SIGRIS system (Salvi et al., 2012), to generate displacement maps and preliminary source models for the emergency management. These results included continuous GPS site displacement data, from private and public sources, located in and around the epicentral area. In this paper we present the results of the geodetic data modeling, identifying two main fault planes for the Emilia seismic sequence and computing the corresponding slip distributions. We discuss the implication of this seismic sequence on the activity of the frontal part of the Northern Apennine accretionary wedge by comparing the co-seismic data with the long term (geological) and present day (GPS) velocity fields.Published645-6551.1. TTC - Monitoraggio sismico del territorio nazionale1.9. Rete GPS nazionale1.10. TTC - Telerilevamento3.2. Tettonica attivaJCR Journalrestricte

Field-induced water electrolysis switches an oxide semiconductor from an insulator to a metal

Here we demonstrate that water-infiltrated nanoporous glass electrically switches an oxide semiconductor from an insulator to metal. We fabricated the field effect transistor structure on an oxide semiconductor, SrTiO3, using 100%-water-infiltrated nanoporous glass - amorphous 12CaO*7Al2O3 - as the gate insulator. For positive gate voltage, electron accumulation, water electrolysis and electrochemical reduction occur successively on the SrTiO3 surface at room temperature, leading to the formation of a thin (~3 nm) metal layer with an extremely high electron concentration of 10^15-10^16 cm^-2, which exhibits exotic thermoelectric behaviour.Comment: 21 pages, 12 figure