Anodic Behavior of Tungsten in H3PO4-K2SO4-H2SO4/KOH Solutions

Authors : Mustafa ANIK

Pages : 915-924

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Publication Date : 0000-00-00

Article Type : Research Paper

Abstract :Potentiodynamic and potentiostatic polarizations were used to study the effect of pH on the anodic reaction characteristics of tungsten insert ignore into journalissuearticles values(W); in a very broad pH range insert ignore into journalissuearticles values(0.4-13);. The open circuit potential was observed to decrease with a constant slope of 58 mV/pH, as pH increased. The oxide phase of W showed typical amphoteric surface behavior in the acidic regime. The oxide dissolution went through a minimum at pH 2.5, which was identified as the point of zero charge insert ignore into journalissuearticles values(pzc); of W--oxide. The oxide dissolution below the pzc was H+ -assisted and above the pzc was OH--assisted. At around the pzc the main dissolution pathway was H2O-assisted dissolution. In basic solutions, in the pH range 7 to 10.5, the hydrated oxide phase dissolution was pH independent. In very basic solutions insert ignore into journalissuearticles values(above pH 10.5);, the dissolution rate of W was observed to increase as pH increased.
Keywords : Turk J Chem, 26, 2002, 915 924 Turk J Chem, vol 26, iss 6