Anodic oxide coatings were synthesised on Ti-6Al-4V substrates using aqueous electrolytes containing dissolved calcium and phosphorus. Different coatings were produced by varying the time of synthesis. Inherent features of the coatings were studied by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). Uniform corrosion, electrochemical polarisation and ac impedance tests were performed in simulated body fluid (SBF). Small amounts of calcium and phosphorus are deposited from the electrolyte on to the coating and their levels increase with increasing duration of synthesis. Maximum values of porosity and thickness are obtained for oxides coated for 3 h. Coatings produced from shorter times showed very good resistance to the attack of SBF. © 2006 Institute of Metal Finishing.

Suresh Krishnamoorthy Seshadri

calcium

corrosion

Electrolytes

Fourier transform infrared spectroscopy

Phosphorus

Porosity

Titanium alloys

Transmission electron microscopy

X ray diffraction analysis

ANODIC OXIDE COATINGS

AQUEOUS ELECTROLYTES

Electrochemical polarization

Simulated body fluid (SBF)

Anodic oxidation

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Corrosion properties of anodic oxide coatings on Ti-6Al-4V in simulated body solution

Transactions of the Institute of Metal Finishing

The current study investigates the effect of crystallite size and surface morphology of TiO 2 nanotubes on their wettability and electrochemical properties. Self-organized amorphous TiO 2 nanotubes were synthesized by anodization process in an acidic (0.5 wt% HF) and a neutral electrolyte (1 M Na 2 SO 4 + 0.5 wt% NaF). Subsequently, the nanotubes were annealed at 450 °C to achieve crystalline phase. Scanning electron microscope micrographs revealed that nanotubes formed from the neutral bath are four times longer (1.2 μm) than the ones synthesized from the acidic bath (325 nm). The charge consumed during anodization is greater under the acidic conditions implying the severity of the attack on the nanotubes by the electrolyte. X-Ray diffraction analysis showed that after annealing TiO 2 crystallizes in the tetragonal lattice as anatase structure. Peak fitting method for line profile analysis was employed to estimate the crystallite size and the micro strain. The oxide nanotubes formed in neutral medium showed smaller crystallite size (28.91 nm) than the one formed in acidic medium (43.37 nm). Wettability measurements showed wetting angles &lt;60°, indicating hydrophilic nature of the anatase nanotubes. Further, both the dimensional aspect (i.e., length and diameter of nanotubes) and the crystallite size have significant effect on the hydrophilic behavior. Electrochemical impedance spectroscopy in a simulated body fluid environment confirmed that structural changes in the oxide layer influence the electrochemical properties. Polarization studies demonstrated that crystallite size affects the passive behavior of the nanotubes. Smaller crystallite size (28.91 nm) lowers the passive current density (0.11 μA cm -2 ), indicating the good protectiveness. © 2015 Elsevier B.V. All rights reserved.

Applied Surface Science

Influence of crystallite size and surface morphology on electrochemical properties of annealed TiO 2 nanotubes

Anodic TiO coatings were produced on Ti-6Al-4V substrates using aqueous electrolytes containing dissolved calcium and phosphorus. Two baths containing Ca and P compounds, in the molar ratios 5 and 15 were used. Different coatings were produced by electrolysis for 3 and 10 h at a constant current density of 10 mA/cm2. X-ray diffraction and X-ray fluorescence were used to identify the phases and chemical composition respectively. Thickness of the coatings was measured using ellipsometry. Electrochemical polarization and AC impedance studies were performed on the coatings by exposing them to simulated body fluid (SBF) for a period of 1 week. The coating produced by 10-h electrolysis from bath of Ca/P ratio 15 showed low corrosion current and high impedance to the week-long attack of SBF. © 2007 Wiley Periodicals, Inc.

Journal of Biomedical Materials Research - Part A

Corrosion of anodic TiO coatings on Ti-6Al-4V in simulated body fluid

Journal of the American Chemical Society

CRC Handbook of Chemistry and Physics:  A Ready-Reference of Chemical and Physical Data, 85th ed Edited by David R. Lide (National Institute of Standards and Technology). CRC Press LLC:  Boca Raton, FL. 2004. 2712 pp. $139.99. ISBN 0-8493-0485-7.

Biomaterials

Accumulation of aluminium in lamellar bone after implantation of titanium plates, Ti–6Al–4V screws, hydroxyapatite granules

Structural characterization of room-temperature synthesized nano-sized β-tricalcium phosphate

Anodic plasma-chemical treatment of CP titanium surfaces for biomedical applications

Structural characterization of nano-sized calcium deficient apatite powders

Journal	Transactions of the Institute of Metal Finishing
ISSN	00202967
Open Access	No