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SAŽETAK
Kompatibilnost titana određena je svojstvima površinskog oksidnog filma
i njegovom stabilnosti u biološkom okolišu. U ovom radu studirana su svojstva
spontano formiranog oksidnog filma na Ti6Al4V i Ti6Al6Nb legurama metodom
impedancijske spektroskopije. Komparativna mjerenja na spektroskopski
čistim komponentama legura: titanu, niobiju i vanadiju provedena su pod
istim eksperimentalnim uvjetima. Utvrđeno je da se legiranjem titana s
niobijem poboljšavaju pasivnost i otpornost materijala prema lokalnoj
koroziji kao rezultat stabilizirajućeg djelovanja Nb-iona na pasivni oksidni
film. Sklonost Ti6Al4V legure prema pitting koroziji pripisana je pojačanoj
difuziji vanadijevih iona i kationskih vakancija kroz oksidni film za
vrijeme lokalnog otapanja pasivnog filma
KLJUČNE RIJEČI
Titan, Ti6Al4V, Ti6Al6Nb, biomaterijali, biookoliš, impedancija, oksidni
filmovi, lokalna korozija
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SUMMARY
The surface oxide film on titanium and its long-term stability in biological
environment plays a decisive role for biocompatibility of titanium implants.
In this study, the passive oxide film formed on Ti6Al4V and Ti6Al6Nb alloys
and its natural growth in a Hank's solution have been investigated by
electrochemical impedance spectroscopy (EIS) measurements. Spectroscopically
pure components of both alloys (Ti, Al, Nb, V) were tested for comparison,
under the same experimental conditions. Alloying titanium with niobium
resulted in improved resistance to pitting corrosion and improved passivation
in comparison to alloying titanium with vanadium, High corrosion resistance
of the Ti6Al6Nb alloy was attribute to the niobium stabilising effect
on the surface oxide on the surface oxide film. The susceptibility of
the Ti6Al4V alloy to pitting corrosion was explained with the enhanced
diffusivity of vanadium ions across the passive layer during passive dissolution.
KEYWORDS
Titanium, Ti6Al4V, Ti6Al6Nb, biomaterials, biological environment, impedance,
oxide films, pitting corrosion
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