PhD Thesis

Corrosion of Ta in Acidic Fluoride Media

• 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

• 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.