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To improve corrosion stability and biocompatibility of titanium surface, hydroxyapatite (Ca10(PO4)6(OH)2, HAP) has been used as coated material because it has similar chemical composition as bone tissue. Incorporation of lignin (Lig) is interesting in medical applications because it leads to thermal stability, hydrophilicity, biocompatibility and biodegrability of different materials. Bioceramic hydroxyapatite/ lignin (HAP/Lig) coatings on titanium were obtained from ethanol suspension by electrophoretic deposition method. The uniform and compact HAP/Lig coatings were deposited at constant voltage of 60 V for 45 s and sintered at 900°C in argon atmosphere. The corrosion stability of sintered HAP/Lig coatings in simulated body fluid (SBF) at 37°C was investigated by open circuit potential-time measurements and electrochemical impedance spectroscopy (EIS). The higer values of open circuit potential, as well as EIS results, indicated improved corrosion resistance and good corrosion stability of HAP/Lig coatings in simulated body fluid at 37°C. Sinteza biokeramičkih prevlaka hidroksiapatit/lignin (HAP/Lig) na titanu vršena je elektroforetskim taloženjem iz etanolske suspenzije. Uniformne i kompaktne HAP/Lig prevlake dobijene su pri konstantnom naponu od 60 V tokom 45s. Nakon sinteze prevlake su sinterovane na 900°C u atmosferi argona. Koroziona stabilnost dobijenih sinterovanih HAP/Lig prevlaka ispitivana je u simuliranoj telesnoj tečnosti (SBF) na 37°C metodom potencijal-vreme i spektroskopijom elektrohemijske impedancije. Ispitivanja su pokazala da sinterovane HAP/Lig prevlake pokazuju dobru korozionu stabilnost u ispitivanom rastvoru.

The corrosion behaviour and thermal stability of epoxy coatings electrodeposited on modified aluminum surfaces (anodized, phosphatized and chromatized-phosphatized aluminium) were monitored during exposure to 3% NaCl solution, using electrochemical impedance spectroscopy (EIS) and thermogravimetric analysis (TGA). Better protective properties of the epoxy coatings on anodized and chromatized-phosphatized aluminum with respect to the same epoxy coatings on aluminum and phosphatized aluminum were obtained: higher values of Rp and Rct and smaller values of Cc and Cd, from EIS, and a smaller amount of absorbed water inside the coating, from TGA. On the other hand, a somewhat lower thermal stability of these coatings was obtained (smaller values of the ipdt temperature). This behavior can be explained by the less porous structure of epoxy coatings on anodized and chromatized-phosphatized aluminum, caused by a lower rate of H2 evolution and better wet ability. Postupkom kataforetskog taloženja dobijene su epoksidne zaštitne prevlake na aluminijumu i modifikovanim površinama aluminijuma (anodizirani aluminijum fosfatirani i hromatno-fosfatirani aluminijum). Za ispitivanje zaštitnih osobina ovako dobijenih epoksidnih prevlaka korišćena je spektroskopija elektrohemijske impedancije i termogravimetrijska analiza. Cilj ovog rada je bio da se objasni uticaj modifikacije supstrata na elektrohemijske karakteristike i termičku stabilnost epoksidnih prevlaka taloženih na aluminijumu.

Using electrochemical impedance spectroscopy, thermogravimetric analysis, gravimetric liquid sorption experiments, differential scanning calorimetry and optical microscopy, the corrosion stability of organic coatings was investigated. It was suggested that electrolyte penetration through an organic coating occurs in two steps. The first step is related to water uptake, when molecules of pure water diffuse in the micropores of the polymer network according to Ficks law, and it is independent of the type and dimensions of ion in the corrosive electrolyte. The second step is related to water and ions penetration through the macropores which leads to contact between the electrolyte and the metal surface and the beginning of electrochemical processes at the metallic interface. Statistical analysis of different layers of the coating through its thickness using optical microscopy and image analysis enabled determination of the pore number, pore size distribution, mean pore diameter, mean pore area and mean percentage of the surface covered by pores. These results suggested the dimensions of the pores through the coating and, knowing the number of the pores on each layer, the quantity of electrolyte inside the macropores was calculated. It was shown that conduction through the coating depends only on conduction through the macropores, although the quantity of electrolyte in the micropores of the polymer network is about one order of magnitude greater than that inside the conductinq macropores. Na osnovu rezultata dobijenih iz spektroskopije elektrohemijske impedancije, termogravimetrijske analize, diferencijalne skenirajuće kalorimetrije, sorpcionih merenja i optičke mikroskopije, ispitivana je koroziona stabilnost polimernih prevlaka i pretpostavljen je mehanizam prodiranja elektrolita kroz njih. U prvom stupnju dolazi do absorpcije molekula vode koji difunduju u mikropore polimerne mreže prema Fikovom zakonu difuzije. U drugom stupnju molekuli vode i joni prodiru kroz makropore u prevlaci do metalne osnove, što dovodi do degradacije prevlake i procesa korozije na supstratu. Takođe su određeni oblik i dimenzije provodnih makropora i izračunat je sadržaj elektrolita u prevlaci.