Estudo comparativo da corrosão em ligas biomédicas

Abstract

The choice of the material for implants is done based on the mechanical resistance, corrosion resistance and according to the in vivo and in vitro tests. In this work the behavior regarding to the corrosion of two alloys already used, Ti-6Al-7Nb and the stainless steel F-138 and three titanium alloys: Ti-6Al-3Nb, Ti-6Al-5Nb and Ti- 6Al-11Nb, was investigated, which has a great potential for prosthetic material despite of not being used yet. The four titanium alloys and the stainless steel F-138 was submitted to the potentiometry test in Ringer solution mean and pH 7.00. Lost weight test was carried out too. The two alloys with worse corrosion rate obtained on lost weight test were submitted to the potentiometry test again. The polarization curve of these samples on second potentiometry test was compared with the polarization curve of samples of the same alloy submitted on potentiometry test only. In the potentiometry test, the Ti-6Al-7Nb alloy was presented the better result on the corrosion resistance, formation of much passivation films in largest potential space than other studied alloys. The Ti-6Al-7Nb alloy was the only not to present pitting corrosion. The lost weight test allowing to obtain the corrosion rate of these alloys: Ti- 6Al-7Nb – 1.17 x 10-3 mm/year, Ti-6Al-11Nb and Ti-6Al-5Nb - 1.29 x 10-3 mm/year both, Ti-6Al-3Nb - 1.40 x 10-3 mm/year and the stainless steel F-138 - 1.44 x 10-3 mm/year. The Ti-6Al-3Nb alloy on second potentiometry test was presented a less corrosion resistance than the sample of same alloy submitted on potentiometry test only. It’s passivation film formatted don’t stopped the increase of the current density. The stainless steel F-138 has been presented a better result than same sample submitted on potentiometry test only. It’s current density was the same obtained to the first potentiometry test but it’s potential space was large. The corrosion resistance of the stainless steel F-138 was inferior to the corrosion resistance of the Ti-6Al-3Nb alloy on the second potentiometry test yet.