1,721,011 research outputs found
Influence of iodide ions on corrosion of dual‐phase steel in sulfuric acid solution
No full textPotassium iodide was studied for its corrosion inhibition property on the corrosion of dual‐phase steel in 0.5M sulfuric acid at 25°C by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. Scanning electron microscopy was used to characterize the steel surface. The inhibition efficiency increases with the concentration of iodide ions. The thermodynamic parameters Kads and ΔG0ads are calculated and discussed. The probable inhibitive mechanism is proposed from the viewpoint of adsorption theory
Investigation of the electrocatalytic behaviour of Fe-MM (MM=Mischmetal) crystalline alloys for hydrogen evolution reaction in alkaline medium
No full textAssessing the corrosion resistance of binary Al–Sc alloys in chloride-containing environment
No full textThe corrosion behaviour of binary Al–Sc alloys (Al-0.3Sc and Al-1Sc, wt%) is investigated in de-aerated 0.6 M NaCl solution, performing potentiodynamic polarisation, potentiostatic transients and electrochemical impedance spectroscopy (EIS) measurements complemented with scanning electron microscopy (SEM). In the presence of chloride ions, both Al–Sc alloys experience localised corrosion (pitting). However, increasing Sc alloying addition leads to an increase of the breakdown potential and the extent of passivation domain, indicating improved resistance to initiation of pitting corrosion. Furthermore, EIS measurements performed at the breakdown state evidenced a higher Rct and a lower depression angle value for the Al-1Sc alloy compared to the Al-0.3Sc one, confirming its better localised corrosion behaviour. Spatial distribution and volume fraction of the Al3Sc secondary phase are microstructural features which play a very important role in determining the corrosion resistance of the Al-1Sc alloy
Investigation of the corrosion behaviour of AISI 3I6L stainless steel sintered in different conditions
No full textRelationship between microstructure, corrosion and tarnish resistance in gold alloys for prosthetic dentistry | Relazione tra microstruttura e resistenza alla corrosione e al tarnish di leghe auree utilizzate in odontoiatria protesica
No full textInfluence of rare earths addition on the corrosion behaviour of Zn-5%Al (Galfan) alloy in neutral aerated sodium sulphate solution
No full textThe effect of rare earth metal (Ce, Er, Y) additions on the corrosion behaviour of Zn–5Al Galfan alloy has been investigated. The corrosion
resistance of Zn–5Al–1Ce, Zn–5Al–1Er and Zn–5Al–1Y alloys has been assessed by various electrochemical tests, such as corrosion potential
measurements, polarization curves and electrochemical impedance spectroscopy. They have been performed in a 0.1M Na2SO4 solution, at
approximately neutral pH, without stirring and in contact with the air. For comparison, the electrochemical tests have also been carried out on the
Zn–5Al alloy. Moreover, the surface morphology and nature of the corrosion products have been investigated. The results indicated that rare earths’
addition improves the corrosion behaviour of Galfan, the effect being more pronounced for the Er- and Y-containing alloys. The mechanism by
which the corrosion resistance of Zn–5Al alloy is enhanced in presence of the rare earths is discussed
Corrosion behaviour assessment of lead-free Sn-Ag-M (M=In, Bi, Cu) solder alloys
No full textThe corrosion behaviour of lead-free Sn88.7Ag2.3In9.0, Sn86.6Ag3.0Bi10.4, Sn96.1Ag3.1Cu0.8 and Sn90.4Ag2.9Cu6.7 solder alloys was investigated in 0.1M NaCl solution and compared with that of the conventional eutectic Sn73.9Pb26.1 solder. Scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) were used to characterize the samples prior and after the electrochemical tests. Potentiodynamic polarization curves show that Sn88.7Ag2.3In9.0 and Sn86.6Ag3.0Bi10.4 solders exhibit poor corrosion behaviour compared to that of Sn73.9Pb26.1. On the contrary, copper addition enhances the corrosion resistance of Sn–Ag solder alloys which exhibit improved passivity behaviour compared to Sn73.9Pb26.1 solder.
Moreover, increasing the copper content from 0.8 to 6.7 at% results in a significant improvement of the corrosion behaviour of Sn–Ag solders.
The presence of tin oxychlorides were detected at the surface of all the alloys investigated after the electrochemical tests. In addition, indium oxychlorides were also observed in the Sn88.7Ag2.3In9.0 solder alloy
A comparative study of methods for the assesment of recovery techniques for aged copper
No full textIn this study an accelerated ageing has been performed on copper sheets successively submitted to different recovering and stabilizing treatments.
The accelerated ageing has been carried out in a climatic chamber for three months with thermal cycles simulating the weather of a desertic country like Egypt (12 h at 60°C with 50% of relative Humidity followed by 12 h at 10°C with 90% of relative humidity) with carbon dioxide flowing; the samples werre buried in silica sand with the addition of sodium chloride in the average amounts of Egyptian sands (about 4 wt%).
On the aged samples the presence of cuprite and copper basic chloride has been detected by X-ray diffraction.
The cleaning techniques employed were: intensive distilled water rinsing, immersion in dilute aqueous sesquicarbonate solution (the solution has been changed until no more chloride was detected), alternate immersions in hydrated ammonia 32% and methyl alcohol (10:90 by volume) solution, and hydrogen peroxide 36 vol. and methyl alcohol (10:90 by volume) solution, and finally, for comparison purposes, electrolysis for total stripping of the corrosion products.
The stabilisation was performed by immersion in 0.01M acqueous solution of 5-amino 2-mercapto- 1,3,4-thiadiazole (AMT) at 60°C followed by repeated washing in water, another set of samples was dipped in a traditional inhibiting solution, 1H-benzotriazole (BTA) in acetone.
The effectiveness of the recovering and stabilization processes has been evaluated by means of 10 and 30 days exposures to three aggressive environments (salt spray, humidostatic chamber, climatic chamber with thermal cycles simulating the climate of unconditioned museum exhibition rooms) and by means of electrochemical tecniques (free corrosion potential and polarization resistance measurements, recording of polarization curves).
The results obtained allow to state that the most suitable recovering and stabilizing techniques seem to be treatments with BTA and AMT inhibiting compounds and that the electrochemical tecniques may be usefully employed to obtain quick indications on the effectiveness of recovering techniques
Electrocatalytic properties of Fe-R (=Rare Earth metal) crystalline alloys as hydrogen electrodes in alkaline water electrolysis
No full textThe electrocatalytic properties of some Fe–R crystalline alloys, Fe90Ce10, Fe90Sm10, Fe90Y10 and Fe90MM10 (MM= mischmetal), were
studied for the hydrogen evolution reaction (HER) in 1MNaOHsolution at 298 K. The microstructure of the electrodeswas examined by optical
microscopy, scanning electron microscopy (SEM) coupled with electron probe microanalysis and X-ray diffraction (XRD) measurements.
The performances towards the HER were investigated by dc polarization and ac impedance techniques. The results were compared with
the G14 (Fe60Co20B10Si10) amorphous alloy, which is a good electrocatalyst material for the HER. The steady-state polarization curves
and electrochemical impedance spectroscopy data showed that high catalytic efficiencies for the HER were achieved on the Fe90Ce10 and
Fe90MM10 electrodes, the latter being a better catalyst as compared with the G14 alloy. Based on the Brewer–Engel valence bond theory, the
improvement of the electrocatalytic performances of the Fe90Ce10 and Fe90MM10 electrodes as compared with the Fe90Y10 and Fe90Sm10 ones
was attributed to synergetic composition effects of the alloys
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