Effect Of Molybdate Ions Research Articles

Anodic electrocrystallization of molybdenum(VI) doped thallium and lead oxides

Molybdenum(VI) doped oxides of p elements, such as thallium and lead, have been synthesized by anodic crystallization. Anodic precipitates based on thallium and lead oxides are shown to contain only a relatively small amount of molybdenum compounds (up to 2 at %) in contrast to mixed manganese and molybdenum oxides (Mn1 -x MoxO2 +x ⋅ nH2O) synthesized by electroprecipitation. The effect of molybdate ions on the electrocrystallization of thallium oxides is most pronounced in the region of threedimensional phase precipitate formation potentials. The introduction of molybdenum(VI) compounds into a solution during the electroprecipitation of lead dioxide induces the formation of precipitates with a much larger spe� cific surface area than individual PbO 2 . The anodic polarization on electrodes with an active layer of molyb� denum doped lead(IV) oxides in the electrolysis of acidic media considerably decreases compared with lead dioxide anodes.

Effect of molybdate ions as corrosion inhibitors of iron in neutral aqueous solutions

Abstract The effect of molybdate ions on the corrosion of Fe in neutral solutions was investigated by electrochemical measurements (dc polarisation and impedance spectroscopy) together with gravimetric determinations. Studies were conducted in solutions containing sodium hydrogen/sodium sulphate salts with molybdate concentrations ranging between 10−4 and 10−2M at pH 8 and 9. Mass loss measurements indicated that about 10−3M of molybdate was necessary in order to inhibit completely the corrosion of Fe at room temperature. The potentiodynamic polarisation and electrochemical impedance studies gave indications about the mechanism of action of the MoO2− 4 ion. They also showed that the inhibiting effect of the oxyanion is increased in the presence of dissolved oxygen. Spontaneous passivation of the corroding Fe electrode could happen only in the presence of dissolved oxygen at concentrations greater than 10−4M. However, passivity was also obtained under potentiodynamic polarisation conditions in deaerated so...

Effect of molybdate ions as corrosion inhibitors of iron in neutral aqueous solutions

Effect of molybdate ions as corrosion inhibitors of iron in neutral aqueous solutions

ChemInform Abstract: The Effect of Molybdate Ions on the Temperature Dependent Pitting Potential of Austenitic Stainless Steels in Neutral Chloride Solutions

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Passivation of titanium in molybdate-containing sulphuric acid solution

The effect of molybdate ions on the passivation reaction of commercial pure (CP) Ti in sulphuric acid solution was studied by conducting an immersion test, measuring dc polarization curves and electrochemical impedance spectroscopy (EIS). It is found that the addition of molybdate in boiling sulphuric acid with concentrations higher than 10 −3 M could greatly reduce the corrosion rate to a negligible value. dc Polarization curves showed that the passivation behaviour was strongly affected by the solution temperature as well as the concentration of molybdate ion present in the sulphuric acid. The passive film resistance ( R pf) determined by EIS was found to increase with the externally applied anodic potential and/or with the molybdate ion concentration. The increase of R pf is mainly attributed to the thickening process of oxide film at more noble potentials.

Effect of molybdate ions on methanation of simulated and natural waste-waters

Sulphate in concentrations of 500 and 1000 mg SO4-S/l did not inhibit methanation of synthetic waste-water (acetate + methanol + glucose) by sludge from a digester treating neutral spent sulphite process effluents. The role of sulphate reducers in the conversion of those substrates was minor although sulphate-reducing bacteria were present with a viable count similar to that of methane-producing bacteria in the sludge. Neutral spent sulphite liquor was partially converted to methane (40% of chemical oxygen demand) under these conditions.

Effect of Molybdate Ion on the Repassivation Kinetics of Iron in Solutions Containing Chloride Ions

Abstract The effect of molybdate ions on the repassivation kinetics of iron has been studied by measuring anodic current transients following in situ film removal by abrasion. In solutions containing both chloride and molybdate ions, it was found that although pits initiate, they do not propagate when molybdate ions are present. Thermodynamic data and electron microprobe analysis suggest that molybdenum improves localized corrosion resistance by forming an insoluble molybdate compound.