Assistant Professor
Department of Chemical Engineering
National Institute of Technology Calicut, India
PhD Thesis
Studies on Corrosion and Anodic dissolution of Ta in Acidic Fluoride Media
The work primarily has two parts:
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First part: The corrosion mechanism of tantalum (Ta) in acidic fluoride media is studied using weight loss experiments performed at various concentrations as well as temperatures.
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Second part: The anodic dissolution mechanism of Ta in acidic fluoride media was studied using potentiodynamic polarization and electrochemical impedance spectroscopy.
Corrosion of Ta in Acidic Fluoride Media
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The corrosion of Ta is studied from conventional weight loss experiments performed at various temperatures and concentrations.
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The key species (HF dissociated species) assisting the corrosion of Ta in acidic fluoride media are identified as (HF2)- and equilibrium HF.
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H2 evolution reaction that occurs during the corrosion process is rapid from the surface of Ta and hence can be neglected.
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A mathematical model to estimate the corrosion rate of Ta is developed.
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Eletcrochemical experiments are performed to measure the corrosion rate or polarization resistance to support the weight loss experiments.
Anodic Dissolution Mechanism of Ta in Acidic Fluoride Media
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The anodic dissolution mechanism of Ta in acidic fluoride media was studied using potentiodynamic polarization and electrochemical impedance spectroscopy
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The anodic polarization was performed in four different concentrations at room temperature and it shows active-passive regions in all concentrations studied.
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The impedance spectra were taken in one active and two passive regions for two concentrations.
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A four step mechanism with two intermediate adsorbed species and two dissolution pathway was developed to describe the anodic dissolution of Ta in active and passive region.
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The mechanistic analysis also shows that the chemical dissolution is assisted by equilibrium HF and electrochemical dissolution is assisted by both undissociated HF and (HF2)- species present in the solution.
