RIVESTIMENTI ANTI-CORROSIVI DI ALLUMINA DEPOSITATI MEDIANTE LETTO FLUIDO

In questo articolo vengono illustrati i risultati di prove di resistenza alla corrosione eseguite su campioni di alluminio AA 6082 T6 rivestiti con un film di Al2O3 depositato mediante letto fluido. Sono state preparate 4 serie di provini con diversi tempi di deposizione (tra 30 e 240 minuti). Le prove di corrosione sono state eseguite mediante Spettroscopia di Impedenza Elettrochimica (EIS), Rumore Elettrochimico (ENA) e Impedenza Elettrochimica Localizzata (LEIS). I risultati hanno evidenziato una migliore resistenza alla corrosione dei campioni trattati fino a 120 minuti, mentre prestazioni più scadenti sono state registrate per i campioni sottoposti a tempi di deposizione superiori

Citric acid aerospace stainless steel passivation: a green approach

Passivation is a common treatment to maximize the corrosion resistance of stainless steel. Nitric acid is generally used and involves several ecological problems, citric acid could be a promising and environmentally friendly alternative to nitric acid. In this work citric acid has been extracted from lemon waste using and eco- friendly procedure. The stainless steel samples have been treated in both nitric and citric acid (commercial and extracted) and corrosion test have been performed. The results show how citric acid can be used as substitute of nitric acid in passivation treatment

Extra-low dosage graphene oxide cementitious nanocomposites: A nano-to macroscale approach

Copyright: © 2021 by the authors. The impact of extra-low dosage (0.01% by weight of cement) Graphene Oxide (GO) on the properties of fresh and hardened nanocomposites was assessed. The use of a minimum amount of 2-D nanofiller would minimize costs and sustainability issues, therefore encouraging the market uptake of nanoengineered cement-based materials. GO was characterized by X-ray Photoelectron Spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR), Atomic Force Microscopy (AFM), X-ray Diffraction (XRD), and Raman spectroscopy. GO consisted of stacked sheets up to 600 nm × 800 nm wide and 2 nm thick, oxygen content 31 at%. The impact of GO on the fresh admixtures was evaluated by rheology, flowability, and workability measurements. GO-modified samples were characterized by density measurements, Scanning Electron Microscopy (SEM) analysis, and compression and bending tests. Permeability was investigated using the boiling-water saturation technique, salt ponding test, and Initial Surface Absorption Test (ISAT). At 28 days, GO-nanocomposite exhibited increased density (+14%), improved compressive and flexural strength (+29% and +13%, respectively), and decreased permeability compared to the control sample. The strengthening effect dominated over the adverse effects associated with the worsening of the fresh properties; reduced permeability was mainly attributed to the refining of the pore network induced by the presence of GO

New Materials and Technologies for Durability and Conservation of Building Heritage

The increase in concrete structures’ durability is a milestone to improve the sustainability of buildings and infrastructures. In order to ensure a prolonged service life, it is necessary to detect the deterioration of materials by means of monitoring systems aimed at evaluating not only the penetration of aggressive substances into concrete but also the corrosion of carbon-steel reinforcement. Therefore, proper data collection makes it possible to plan suitable restoration works which can be carried out with traditional or innovative techniques and materials. This work focuses on building heritage and it highlights the most recent findings for the conservation and restoration of reinforced concrete structures and masonry buildings

Electrochemical noise for corrosion detection

In the last years, a growing interest on the use of Electrochemical Noise (EN) for corrosion studies may be detected in the main literature. As a result of this, several methods for analyzing noise data have been developed. In this paper a review of the investigative possibilities offered by EN in the field of corrosion is given. All the experimental data reported are from research projects developed in our laboratory where, for more than 15 years, EN has been applied to the solution of different corrosion problems and some dedicated software have been developed for EN data analysis (FFT-MEM, PSD slope detection, discriminant analysis). Much attention will be given to the use of statistical parameters and their significance in terms of corrosion behavior of the electrode. Moreover, the experimental caution to use in order to have meaningful data will be highlighted

The use of electrochemical noise analysis on corroding systems

This paper gives an overview of the use of Electrochemical Noise (EN) for corrosion studying and monitoring. Since the quality and reliability of noise data are affected by a number of acquisition parameters, such as sampling interval, sampling duration, D.C. trend and instrumental noise, some experimental and practical aspects were discussed. The use of statistical parameters such as standard deviation, Pit Index and/or Localization Index and Noise Resistance to analyze noise data of corroding systems were examined. Many experimental applications of Electrochemical Noise Measurements on different metals and alloys were given. EN data have been compared with traditional electrochemical techniques. EN allowed to characterize the corrosion behavior of samples giving in some cases good quantitative estimation. The transposition of current and potential noise acquisition in the frequency domain (by Fast Fourier Transform and/or Maximum Entropy Method), gave further information on corrosion mechanism and in particular permitted to identify the type of corrosion. Finally the use of Discriminant Analysis permitted to deduce the best sampling frequency and sampling duration for EN acquisition, able to discriminate between two different situations

A crevice corrosion study by electrochemical noise analysis

The use of the Electrochemical Noise Analysis (ENA) for the evaluation of crevice corrosion is illustrated in the case of AISI 430 stainless steel in 3% sodium chloride. A crevice former was used in order to induce a crevice corrosion attack. Current and potential noise signals were simultaneously recorded allowing the determination of the noise resistance (Rn). ENA was able to detect the four stages mechanism of crevice corrosion. The comparison of Rn with the Polarization Resistance (Rp) determined by Electrochemical Impedance Spectroscopy (EIS) gave good agreement in particular during the initiation and propagation of the attack. The evaluation of the noise data in the frequency domain gave interesting results in particular in the evaluation of the roll-off slopes in the Power Spectrum Density (PSD) plot that are correlated to the corrosive status. Finally a new analysis for noise data is shown. The application of spectral ratio discriminant function to noise data in the frequency domain, permits to deduce the best sampling frequency and sampling duration for ENA acquisition, able to discriminate between two different situations