Increasing temperature accelerates Ti-6Al-4V oxide degradation and selective dissolution: An Arrhenius-based...

Area of Science:

• Materials Science
• Biomaterials Engineering
• Corrosion Science

Background:

• Selective dissolution of Titanium-Aluminum-Vanadium (Ti-6Al-4V) alloy occurs in orthopedic implants, but current pre-clinical tests fail to replicate this damage.
• Ti-6Al-4V is widely used in implants, including additively manufactured devices, and understanding its corrosion is critical for patient safety.
• Existing testing methods do not accurately predict in vivo corrosion, highlighting the need for accelerated and reliable pre-clinical evaluations.

Purpose of the Study:

• To develop an accelerated pre-clinical methodology using elevated temperatures to rapidly induce Ti-6Al-4V selective dissolution.
• To investigate the structure-property relationship between the dissolving alloy surface and its oxide layer under varying temperatures.
• To establish a correlation between accelerated testing conditions and physiologically relevant corrosion mechanisms.

Main Methods:

• Electrochemical impedance spectroscopy (EIS) was used to monitor the oxide film's degradation and polarization resistance (Rp) at 24 °C, 37 °C, and 45 °C.
• Scanning electron microscopy (SEM) quantified the extent of selective dissolution based on EIS data.
• An Arrhenius approach was employed to relate corrosion rates at different temperatures to physiologically relevant conditions.

Main Results:

• Electrochemical impedance spectra showed significant decreases in Rp over time and with increasing temperature, indicating accelerated oxide degradation.
• Corrosion rates increased in an Arrhenius-dependent manner with rising temperatures.
• Three distinct surface classes (undissolved, transition, dissolved) were identified, correlating with changes in oxide properties.

Conclusions:

• Elevated temperatures can accelerate Ti-6Al-4V selective dissolution, providing a viable method for pre-clinical testing.
• A clear temperature and concentration-dependent relationship exists between the corrosive solution, the oxide film, and the substrate alloy.
• Supraphysiological temperatures can induce dissolution patterns similar to physiological conditions but in significantly reduced experimental times.