Effect of HF Concentration on Anodic Dissolution of Titanium. Issue 4 (31st January 2017)

• Record Type: Journal Article
• Authors: Amrutha, M. S.; Fasmin, Fathima; Ramanathan, S.
• Is Part Of: Journal of the Electrochemical Society. Volume 164:Issue 4(2017)
• Page Start: H188
• Page End: H197
• Publication Date: 2017-01-31
• Subjects: anodic dissolution -- corrosion -- hydrofluoric acid -- reaction mechanism -- Titanium; Electrochemistry -- Periodicals; 541.3705
• DOI: 10.1149/2.0501704jes
• Languages: English
• ISSNs: 0013-4651

Abstract

Abstract : Anodic dissolution of Ti metal in varying concentrations of hydrofluoric acid (10–1000 mM HF) was investigated using potentiodynamic polarization and electrochemical impedance spectroscopy. Polarization curves obtained at all concentrations of HF solution showed that current initially rises with potential, and decreases at higher potentials. Complex plane plot of the impedance spectra of Ti dissolution in 25 and 50 mM HF solutions exhibited three capacitive loops in the active region and a capacitive behavior with negative resistance in the passive region. The surface was characterized using X-ray photoelectron spectroscopy. A four step mechanism with chemical and electrochemical dissolution steps was employed to model Ti dissolution. The analysis shows that the simulated results match the polarization trends satisfactorily in all the solutions investigated. The model predicts that HF - 2 and remaining HF are the species that influence chemical and electrochemical dissolution steps respectively. The estimates of surface coverage values of the adsorbed species showed that with increasing over potential, the metal surface was progressively covered with oxide film, while an increase in nominal HF concentration leads to a decrease in fractional surface coverage.