Product hydroxyapatite (HAP) coatings on 316l LSS and Ti implants use by sol-gel process, corrosion behaviours investigate by electrochemical methods

In this research, hydroxyapatite (HAP) coatings have been produced on Ti and Ti6Al4V alloy and 316 L stainless steel subsrates by sol-gel method. HAP powders have been obtained from two different sources. Ca(OH)2 is taken as Ca precursor and H3PO4 is taken as P precursor in order to obtain 2,5% and 5% HAP coatings .NH4H2PO4 is taken as P precursor and Ca(NO3)2.4H2O is taken as Ca precursor to obtain normal HAP coating. Additionaly three different pre-surface processes (HNO3, anodic polarization , 5 N NaOH ? 1N HCI (BA)) have been applied to Ti and Ti6Al4V alloy and 316L stainless steel subsrates. The corrosion behaviours of bare and HAP plated samples are examined in Ringer and 0.9% NaCI. Consequently, HAP coatings have obtained pure Ti over 82.9% inhibition and the corrosion of Ti6Al4V alloy has obtained over 89,49% and over inhibition. In Ringer solution, 96,5% inhibition has been obtained in HAP plated anodic pre-surface proceeded sample for 316 Lstainless steel, 67,74% inhibition has been achieved in HAP plated HNO3 pre-surface proceeded sample in NaCI medium and 78,13% inhibition has been obtained in 5% HAP plated BA pre-surface proceeded one . All pre-surface processes are effective on moniyoring corrosion and clinging of HAP coting to the surface. In 316 L steel however, anodic pre-surface process is effective in Ringer medium. On the other hand, HNO3 and BA pre-surface process is effective NaCI medium . It is seen that impedance values have increased in HAP coatings (Ti and Ti6Al4V). HAP coatings have raised the resistance of the metals. The values of polarization resistance in HAP plated samples have increased for 316L stainless steel in 0,9% NaCI and Ringer solutions. It is seen in SEM images that open pores and attachments among pores have been observed inthe coating, which increases osteointegration. It is noted in EDX analyses of the surfaces of the HAP plated samples that there is only Ca, O and P on the surface. Ca\P ratio varies in 1,36-2,00 ranges. As Ca\P ratio increases, the inhibition increases too. It is seen in XRD images of HAP powder that there are rutil, HA and ß calcium phosphate structures. And it is observed in XRD peak of the powder obtained from 5% HAP isopropanol solution that there are HAP crystal and ?-tri-calcium phosphate ß calcium phosphate. Additionally, it is seen in FTIR analysis, characteristic HA absorption bands have occurred in all the sintered powders.Key words: Titanium, 316LSS(Stainless Steel), implant, HAP coating, sol-gel method.