CORROSION BEHAVIOUR OF TITANIUM ALLOY Ti-6Al-4V ELI IN HANK'S SOLUTION WITH THE IMMERSION TEST METHOD

The titanium Alloy Ti-6Al-4V ELI is a biomaterial with high tensile strength, good corrosion resistance, and high yield strength. However, it can trigger corrosion when attached to the implant for a long period. The ions in the metal will be released into the corrosive solution and cause toxicity to the human body. This research measured the metal ion transfers from TI-6AL-4V ELI to Hanks' Balanced Salt Solution (HBSS) to determine the duration needed by the ions to start the transfer. Knowing such data is beneficial to prevent the ions from poisoning the body. The test ran in vitro, where Ti-6Al-4V ELI was immersed into the HBSS for three different periods. Prior to immersion, the sample's pre-corrosion condition was tested through sanding, dimension measurements, weighing, and monitoring the surface morphology. After immersion, the post-corrosion test was carried out by observing the corrosion beams on the sample surfaces and calculating the rate of corrosion and the metal ions discharged into the corrosive solution. The research results indicated that the 2-week immersion resulted in the lowest corrosion rate, namely 6.3 x 10-6 mmpy; meanwhile, the 6-week immersion showed the highest rate, namely 6.5 x 10-6 mmpy. In other words, the longer the immersion period, the higher the corrosion rate. Furthermore, the calculation of the metal ions showed the element released the most was Ti, reaching 1.0 x 1017 atoms/L. There was also an element out of the Ti-6Al-4V ELI contents, namely Si. Hence, the immersion time is very influential on the element mass transfer into the solution.