16. Protection and functionalization of AISI 316L for orthopedic implants

SHEILA OMAR; JOSEFINA BALLARRE; SILVIA CERE

Troia

Simposio; 11th International Symposium on Electrochemical Methods in Corrosion Research, EMCR 2015; 2015

Sociedad Internacional de Electroquimica

Orthopedic devices forpermanent implants require short term fixation and fast bone attachment andhealing. Surface modification of surgical implants is often used as a tool togenerate a protective barrier along with the possibility of providingintegration of the metal to the human body. This integration can be enhancedcreating a bioactive surface able to produce a natural bonding between themetal and the existing bone. One possibility in the surface modification ofmetallic implants is the creation of organic-inorganic hybrid coatings as a wayto improve the prosthesis performance. It has been demonstrated that SiO2 based coatings, obtainedfrom tetraethylorthosilicate (TEOS) and methyltriethoxysilane (MTES) improvethe corrosion behavior of the AISI 316L stainless steel in biologicalenvironments.  The hybrid layers of TEOSand other silanes are not bioactive by themselves but they can befunctionalized with particles that can induce bioactivity. It has been proved thatcoatings functionalized with a bioactive ceramic or glass-ceramic from theCaO-SiO2-P2O5 system can maximized the hydroxyapatitedeposition rate. This work presents thesynthesis and deposition of sol-gel coating, with an initial solutioncontaining TEOS, MTES and colloidal silica nanoparticles, applied on AISI 316L stainlesssteel by dip-coating as a first layer with the aim of providing the corrosionprotection of the substrate. A heat treatment of 30 min at 450 ºC was performedto consolidate this protective layer. On the top of this coating a potentiallybioactive glass (58S) made also by sol gel method with TEOS, triethyl phosphate(TEP) and calcium nitrate as precursors, was applied by spray techniquedeposition using comprised air as carrier with a high efficiency filter. Thismethod allows the creation of a wide distribution of particles sizes over thetarget. A stabilization treatment at 450 ºC for 3 hours was held to ensure theglass formation and nitrate and residues elimination.Coatings are characterizedby profilometry and optical and electronic microscopy. The surface integrityand corrosion resistance of the coatings in time is analyzed by electrochemicaltests together with the solubilization of the particles in simulated body fluid(SBF).