The influence of aggressive media and inflammatory processes on the corrosion of biocompatible metal implants in artificial saliva

V magistrskem delu smo proučevali korozijo biokompatibilnih kovinskih implantatov v umetni slini. Nerjavno jeklo AISI 316L in titanovo zlitino Ti90Al6V4 smo korodirali v umetni slini, v katero smo dodajali spojine, ki jih običajno s hrano in pijačo vnašamo v ustno votlino ali nastajajo kot produkt vnetnih procesov in predstavljajo precej agresiven medij za kovinske implantate. Dodajali smo NaCl različnih koncentracij ter HCl, s katero smo vplivali na vrednosti pH. Vnetno stanje v ustni votlini smo simulirali z dodatkom H2O2 in mlečne kisline različnih koncentracij. Korozijske parametre smo spremljali s potenciodinamsko metodo in elektrokemijsko impedančno spektroskopijo. Vzorce smo pri konstantni temperaturi, 37 °C, potopili v izbrani medij, kjer smo jih pasivirali 24, 48, 72 in 96 ur. Izvedli smo tudi meritve nepasiviranih vzorcev. Na podlagi pridobljenih meritev smo vzorcem določili hitrost korozije in jih glede na vrednosti korozijskih parametrov medsebojno primerjali. Ugotovili smo, da so bile korozijske hitrosti relativno nizke, kar dokazuje zelo dobro korozijsko odpornost uporabljenih materialov, zato sta materiala primerna za dentalne implantate. Prav tako smo ugotovili, da je titanova zlitina korozijsko odpornejša kot nerjavno jeklo v vseh proučevanih medijih, razen v umetni slini s 5 % in 10 % H2O2 z mlečno kislino. Opazili smo tudi, da se korozijske hitrosti znižujejo in zvišujejo glede na čas pasiviranja, kar je najverjetneje posledica spreminjanja debeline zaščitne oksidne plasti na površini.In this thesis we studied the corrosion of biocompatible metallic implants in artificial saliva. Stainless steel AISI 316L and titanium alloy Ti09Al6V4 were corroded in artifical saliva, to which we added substances introduced to the oral cavity by foods and drinks or produced by inflammation processes, and represent an aggressive media for metal implants. Different concentrations of NaCl were added, as well as HCl to alter the pH values. The inflammation state in the oral cavity was simulated by addition of H2O2 and lactic acid in different concentrations. The corrosion parameters were identified by the potentiodynamic method and the electrochemical impedance spectroscopy. The samples were immersed in the selected media at a constant temperature of 37 °C and were left to passivate for 24, 48, 72 and 96 hours. Measurements on non-passivated samples were also conducted. On the basis of the conducted measurements, corrosion rates of the samples were determined. Samples were also compared to each other by the values of corrosion parameters. The research showed that the corrosion rates were relatively low, which accounts for the very good corrosion resistance of the studied materials and that the materials are adequate as dental implant materials. Additionally, we noticed that the titanium alloy was less susceptible to corrosion than stainless steel in all the studied media except in artificial saliva with 5 % and 10 % H2O2 with lactic acid. We also noticed the corrosion rates decrease and increase in dependence on the time of passivation, for which the changes in thickness of the protective oxide layer are probably the cause