Breakdown of Passive Films and Repassivation of Ti-6Al-4 V Alloy with Rapid Elongation in Simulated Body Fluid including Osteoblast-like Cells

• Published in: Journal of the Electrochemical Society Vol. 160; no. 11; pp. C576 - C580
• Main Authors: Doi, Kotaro, Miyabe, Sayaka, Fujimoto, Shinji
• Format: Journal Article
• Language: English
• Published: The Electrochemical Society 01.01.2013
• ISSN: 0013-4651; 1945-7111
• DOI: 10.1149/2.085311jes

Breakdown of passive films and repassivation of Ti-6Al-4 V alloy in a simulated body environment were examined using a rapid straining electrode test. Samples previously immersed in cell culturing medium with or without cells were elongated rapidly with a straining rate of 0.67 s−1. The transients of stress, strain and current were recorded during and after elongation. Larger charge density after elongation was observed on samples immersed longer in the simulated body fluid and covered with cells. It is supposed that the proteins and cells that adhered on the sample surface hinder the repassivation. An occluded space is formed between proteins and cells and substrate alloy. Since the diffusion is blocked in the occluded space, the pH becomes lower in this space as the result of hydrolysis of dissolved cations. Therefore, the repassivation is hindered and a localized corrosion occasionally occurred along slip step under cells and proteins. Localized corrosion occurred after elongation when applied potential is more noble than some critical potential, which could not be determined with conventional electrochemical tests.