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  • 1
    Electronic Resource
    Electronic Resource
    Anodization of molybdenum. II. Electrical breakdown (1987)
    Springer
    Journal of applied electrochemistry 17 (1987), S. 899-904 
    Details
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The breakdown phenomenon during galvanostatic anodization of molybdenum has been investigated. The effect of current density and the electrolyte composition and concentration on the breakdown voltage,E B, was studied.E B was found to depend on the electrolyte composition and resistivity and not on the anodizing current density. The empirical relation betweenE B and the logarithm of electrolyte resistivity, ϱ $$E_B = a_B + b_B \log \varrho $$ was fairly valid. Post-breakdown anodization experiments showed that the breakdown characteristics are independent of the history of the anodic film formation. Also, an increase of sparking time,T B, leads to: (i) shift of the zero time potential in the second electrolyte,E 2 0 , towards higher values; and (ii) decrease of the electrode capacitance. Such findings may be taken as evidence for the covering of the breakdown spots with thicker films.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01024355
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  • 2
    Electronic Resource
    Electronic Resource
    Anodization of molybdenum. I. Galvanostatic anodization (1987)
    Springer
    Journal of applied electrochemistry 17 (1987), S. 1065-1074 
    Details
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Molybdenum was anodized at different current densities (10−4–10−2 A cm−2) in various aqueous solutions. Potential-time curves obtained in strong acid solutions are similar to those usually reported for the valve metals, and the anodization kinetics were found to obey the familiar exponential law $$i = A \exp BH$$ and also to obey the empirical relation, $$(dE/dt)_i = a(i)^b $$ Using both polarization and capacitance measurements, it was found that the field strength,H, the electrolytic parametersA andB and the constantsa andb are comparable with those previously reported for many valve metals. Except in strong acid solutions,E-time curves showed an induction period before oxide formation. The duration time of the induction period,t i, was found to increase with decrease of solution acidity and current density and with increase of temperature. Although chloride ion may act as a depolarizer,t i was found to decrease with increase of chloride ion concentration, probably by increasing the anodization field strength.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01024372
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  • 3
    Electronic Resource
    Electronic Resource
    Passivity of α-brass (Cu∶Zn/67∶33) and its breakdown in neutral and alkaline solutions containing halide ions (1991)
    Springer
    Journal of applied electrochemistry 21 (1991), S. 829-836 
    Details
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The passivation behaviour of α-brass (Cu∶Zn=67∶33) in alkaline solutions was studied using cyclic voltammetry and potentiostatic current transient measurements. The recorded cyclic voltammograms exhibited the main features usually observed for pure copper and zinc, and one additional anodic peak on the reverse potential scan. The height, sharpness and location of the different peaks depended greatly on the alkali concentration and the scan rate. The results show that the formation of Cu2O and Cu(OH)2 films proceed under ohmic resistance control following a dissolution-precipitation mechanism. The effect of F−, Cl− and Br− ions on the passivity was also studied. The pitting potential was found to decrease with logarithm of halide ion concentration. The current transients in the absence and presence of halide ions were analysed. In the absence of pitting the current, after a few seconds, was found to increase linearly with the reciprocal of the square root of time while in the presence of pitting it was found to fit the Engell-Stolica equation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01402821
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  • 4
    Electronic Resource
    Electronic Resource
    Evidence for anodization kinetics of molybdenum as a valve metal in buffer solutions of pH 9.3 (1988)
    Springer
    Journal of applied electrochemistry 18 (1988), S. 312-313 
    Details
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01009280
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  • 5
    Electronic Resource
    Electronic Resource
    Kinetics of the dissolution behaviour of anodic oxide films on niobium in NaOH solutions (1987)
    Springer
    Journal of applied electrochemistry 17 (1987), S. 559-566 
    Details
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The dissolution behaviour of the anodized niobium electrode in NaOH solutions was investigated as a function of alkali concentration, formation voltage, formation current density and temperature using potential and impedance measurements. The rate of dissolution is dependent on the alkali concentration. In dilute NaOH solutions (1 N) the anodic oxide film formed in 0.5 M H2SO4 is reasonably stable. On the other hand, at higher concentrations of NaOH (≥2 M), the anodized electrode is subject to continuous dissolution depending on the alkali concentration. Also, the dissolution process is considerably affected by temperature; at temperatures greater than 320 K the oxide film is destroyed in less than 30 min. The results show that the current density used during the formation of the oxide film has no effect on its dissolution rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01084130
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  • 6
    Electronic Resource
    Electronic Resource
    A kinetic study on the corrodability of anodic oxide films formed on molybdenum in NaOH solutions (1988)
    Springer
    Journal of applied electrochemistry 18 (1988), S. 86-91 
    Details
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The corrodability of anodic oxide films formed on molybdenum in NaOH solutions was studied using impedance and potential measurements. The corrosion rate was found to increase with increase of alkali concentration, film thickness and temperature and was nearly independent of the rate of oxide formation. The dissolution process was found to involve a valency change from Mo(IV) to Mo(VI) where it seemed, from cathodic polarization, that no electron transfer through the oxide film to/from the metal surface was involved during the dissolution process. In concentrated NaOH solutions ([OH−]≧9 M), the dissolution process appeared to follow zero-order kinetics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01016209
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  • 7
    Electronic Resource
    Electronic Resource
    Nature and stability of anodic oxide films formed on molybdenum in chloride solutions (1988)
    Springer
    Journal of applied electrochemistry 18 (1988), S. 441-446 
    Details
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The formation and stability of anodic oxide films on molybdenum in chloride solutions was tested using impedance and polarization measurements. The efficiency of oxide formation increases as the acidity of the formation medium increases. The film is highly stable and resistive to attack and dissolution regardless of the chloride concentration, pH or film thickness. The corrosion potential did not vary with variation of immersion time, solution composition or film thickness and recorded ≃0.000V vs SCE indicating the high insulating properties of the film. Polarization measurements on previously anodized molybdenum electrode showed that the electrode is ideally polarized over a potential region not less than 2V. The magnitude of that potential region increases as the film thickness increases. The anodic film cannot be reduced or removed by galvanostatic cathodic polarization. The impedance behaviour of the anodized molybdenum electrode was found to be purely capacitive and the oxide film may be treated approximately as a perfect dielectric material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01093760
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  • 8
    Electronic Resource
    Electronic Resource
    Influence of oxide bond energies on the kinetics of chemical dissolution of anodic oxides on valve metals (1988)
    Springer
    Journal of applied electrochemistry 18 (1988), S. 532-537 
    Details
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The influence of M-O bond energies on the kinetics of the chemical dissolution of anodic oxide films on valve metals was analysed and the different profiles of atomic defects in these oxides were deduced. Four different equations describing the dissolution behaviour of such oxides were derived and the respective examples justifying each equation were also introduced. For many oxides, M-O bond energy was found to vary linearly with the activation energy of the dissolution. It was also found that the dissolution rate increases with increase of the initial thickness of the oxide. The dissolution processes were followed by using potential and capacitance measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01022247
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  • 9
    Electronic Resource
    Electronic Resource
    Stability of anodic tantalum oxide films in NaOH solutions (1989)
    Springer
    Journal of applied electrochemistry 19 (1989), S. 768-776 
    Details
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The dissolution behaviour of the anodic oxide films formed on tantalum was investigated in NaOH solutions of different concentrations. In solutions of [OH−]〈3.0 M, no pronounced dissolution could be detected. However, in concentrated alkali solutions, [OH]〉3 M, the dissolution occurred to different extents depending on the alkali concentration. As observed from capacitance and potential measurements, the barrier film on Ta was found to be defective owing to the incorporation of OH− ions in the film. The nature of the barrier film and its dependence on formation rate, alkali concentration and solution temperature were investigated. Complex plane analysis illustrates the behaviour of the barrier film of different thickness, i.e. formation voltages, in NaOH solutions. The barrier film cannot be considered accurately as a perfect dielectric.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01320653
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  • 10
    Electronic Resource
    Electronic Resource
    Inhibition of corrosion of α-brass (Cu-Zn, 67/33) in acid chloride solutions by some amino pyrazole derivatives (1989)
    Springer
    Journal of applied electrochemistry 19 (1989), S. 928-932 
    Details
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The inhibition of corrosion of commercial 67/33 brass in 0.1m HCl acid solutions by some amino pyrazole derivatives was tested using polarization, capacitance and weight-loss measurements. The amino pyrazole derivatives were 3(5)-amino, 5(3)-phenyl pyrazole; 3(5)-amino, 5(3)[4--chlorophenyl] pyrazole; 3(5)-amino, 5(3)[4--methoxy phenyl]pyrazole; 3(5)-amino, 5(3)[4--methyl phenyl]pyrazole; 3(5)-amino, 5(3)-cyano pyrazole; and 3(5)-amino, 4-phenyl-5(3)-methyl pyrazole. The results showed that these compounds predominate as cathodic inhibitors and inhibition efficiencies up to 91% can be obtained. The inhibition was assumed to occur via chemisorption of the inhibitor molecules fitting a Temkin isotherm. The influence of the substituent group on the inhibition efficiency of the inhibitor was explained in terms of the density of the electron cloud on the pyrazole ring and the mode of adsorption. Although increase in temperature was found to decrease the corrosion in the absence of the inhibition, it increased in the presence of inhibitor, probably via desorption of the inhibitor molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01007942
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