Corrosion behaviour of Terfenol-D

The corrosion behaviour of pseudo-binary compound Tb_0.3Dy_0.7Fe_1.92 (Terfenol-D) was studied in 3.5% NaCl and 0.01 N Na₂SO₄ solutions using Tafel polarisation, linear polarisation, electrochemical impedance spectroscopy and weight loss techniques. Electrochemical testing revealed the adverse effect of chloride ions, as corrosion rates were higher in 3.5% NaCl solutions than in 0.01 N Na₂SO₄ solutions. The effect of aeration was studied by conducting experiments in freely-aerated, deaerated and fully-aerated conditions. Absence of oxygen accelerated corrosion in chloride environment, due to increased hydrogen interaction in presence of destabilised surface films. The improved corrosion resistance in chloride-free environment was correlated with morphological features of the corroded surfaces. Micro-compositional analysis of the corrosion products revealed that the corrosion products were primarily rich in rare earth elements. A comparison of all experimental techniques showed that Tafel extrapolation and EIS techniques provided reliable estimates of corrosion rate.     

Improving the formation and protective properties of La-conversion coatings on brass by use of La2O3 nanoparticle incorporation with electrodeposition

The La₂O₃ nanoparticles incorporation and electrodeposition were used together to prepare the La-conversion coatings on brass surface in a basal solution containing rare earth salt and benzotriazole. The results showed that both of these techniques can improve the coatings formation and their protectiveness. A critical nanoparticulate La₂O₃ content and a critical deposition potential were observed, under which the conversion coatings had the highest protective properties. The composite La-conversion coatings could provide important protection against brass corrosion for considerable immersion periods in 3.5% NaCl solution because it ennobled the corrosion potential and decreased the anodic current.     

The effect of impurity inclusions on the pitting corrosion behaviour of beryllium

An electrochemical polarisation study has been conducted to determine the effect of impurity inclusions on the pitting corrosion behaviour of beryllium. Three grades of commercial beryllium differing in impurity levels were used. This work showed a strong relationship between the pitting potential of the beryllium and the level of impurity inclusions, the grade with the least number of overall inclusions being the most resistant to pitting corrosion. The work also revealed the preferred sites for pit initiation, with most corrosion pits initiating at intermetallic Fe/Al/Be inclusions, and to a smaller extent at inclusion sites containing either elemental silicon or carbides.     

Hydrogen evolution reaction on spheroidal graphite cast iron with different pearlite areas in sulphuric acid solutions

The rate equation of hydrogen evolution reaction of spheroidal graphite cast iron with different pearlite area has been studied in sulphuric acid solutions at 298 K. The cathodic Tafel slope of ?0·130 V/decade and the reaction order with respect to the activity of hydrogen ion of 1 are obtained by linear potential sweep technique. The rate equation of hydrogen evolution reaction does not depend on the area of pearlite. There is no difference in hydrogen evolution reaction mechanisms between pure iron and spheroidal graphite cast iron.     

Factors influencing electrode potential of steel in concrete

Abstract

An investigation of the rusting of steel wire in concrete and mortar is reported. Steel corrosion was monitored using electrode potential measurements, and five experimental parameters were controlled: cement type, mortar porosity, mortar cover thickness, mortar cracking, and carbonation thickness. Measurements were made by connecting the reference electrode to three locations on each face of every reinforced mortar parallelepiped sample. The results showed that the mean value of the electrode potential for a sample is correlated with the degree of rusting of the steel, although the location of the measurement does have some effect on the recorded electrode potential. Cracking of the mortar has also been shown to influence the electrode potential.     

Phytate as efficient and green corrosion inhibitor for NdFeB magnets in aqueous salt solution

Phytate had been investigated as a corrosion inhibitor for NdFeB magnets in an aqueous salt solution. Potentiodynamic polarisation, electrochemical impedance spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and energy dispersive spectroscopy were employed for this investigation. The polarisation curves results revealed that phytate acted as a mixed type inhibitor. The inhibition efficiency was found to increase by maximum 96.5% through increasing the phytate concentration to 0.5?mM at 30°C. The inhibition was proposed to result from the adsorption of phytate on NdFeB magnets, which was found to obey the Langmuir adsorption isotherm. The inhibition mechanism was explored by the potential of zero charge (E_pzc) measurement at the solution/metal interface.     

Effect of nitrogen on crevice corrosion in austenitic stainless steel

Corrosion properties of high nitrogen austenitic steels in chloride solutions have been investigated. Nitrogen behavior was evaluated at various electrode potentials, and analysis of the surface film was carried out with XPS. The alloy used for the experiments had a composition of 23%Cr-4%Ni-0-1%Mo-0.7-1%N and was obtained through electro-slag remelting (ESR) under high nitrogen pressure. High nitrogen austenitic steel produced in the solution by crevice corrosion under a constant potential of 0.2 V (SCE). In the transpassive region and at 0.7 V (SCE), the products in the solution were , and . The amount of dissolved and increased with the electrode potential. in the solution suppressed decreases of pH, having a re-passivation effect. For crevice corrosion under a higher electrode potential than 0.4 V (SCE), the number of crevice corrosion points and the corrosion loss decreased as the electrode potential increased. This behavior can be attributed to the corrosion suppressing effect of dissolved in the solution as a product of crevice corrosion. The presence of chromium and iron oxides in the passivation film and crevice corrosion surface film were identified from XPS analysis. N 1s spectra indicated the presence of a nitride (CrN) or NH₃.     

Corrosion behaviour of stainless steel fibre-reinforced copper metal matrix composite with reference to electrochemical response of its constituents

In this study, the corrosion behaviour of stainless steel fibre-reinforced copper metal matrix composite was investigated in chloride media at different temperatures and pH values using electrochemical techniques. The results were demonstrated in terms of the electrochemical response of the composite constituents. Microstructure observations of free corroded samples showed that the corrosion initiated at the copper matrix. Galvanic current density measurements demonstrated equilibrium polarity in which copper acted as the cell anode. The corrosion behaviour of the composite was predominantly determined by copper.     

More accurate simulation of dynamic transparent optical wavelength division multiplex networks

Novel modulation schemes and higher bit rates as well as dynamically switched networks make it necessary to consider effects, which could be neglected in system simulations so far. In this paper, we present simulation methodologies needed for the accurate characterisation of the signal quality in such transparent optical networks.The combined effects of polarisation mode dispersion (PMD) and polarisation-dependent loss (PDL) are investigated, and a more accurate method for the BER estimation based on histograms is described. Furthermore, dynamical transient effects in the physical layer require extending the regarded time scale to the millisecond range. An efficient way how to simulate the effects on different time scales is presented.     

Effects of rare earth metal addition on surface morphology and corrosion resistance of hot-dipped zinc coatings

Effects of rare earth metals (REM) addition on surface morphology and corrosion resistance of hot-dip galvanised steel were investigated. The corrosion resistance of steel samples galvanised with zinc and zinc alloys containing 0.05, 0.1, 0.2 and 0.5 wt.% REM were evaluated by various corrosion tests such as weight loss in salt spray chamber and natural sea water, sacrificial protection ability in contact with fog in salt spray chamber and after immersion in sea water, potential-time in sea water and linear polarisation in sodium chloride solution. Surface morphology and nature of the corrosion products were also investigated. The results indicated that the addition of small amounts of REM to the molten zinc galvanising bath can improve the corrosion resistance of hot-dip galvanised steel. Mechanisms by which the corrosion resistance of hot-dip galvanised steel are improved in presence of REM have been discussed.