A sol-gel based bioactive glass coating on laser textured 316L stainless steel substrate for enhanced biocompatability and anti-corrosion properties

Abstract

In this study, we have synthesized a new family of bioactive glass (BAG) comprising of SiO2, Na2O, CaO, K2O, P2O5 and MgO via sol-gel route. The composition of these oxides has been selected in such a way that the BAG has a coefficient of thermal expansion close to the 316L stainless steel (SS). In vitro test by soaking the BAG in simulated body fluid (SBF) showed good bioactivity due to ion exchange between alkali ions from the BAG and the ions present in the SBF. The 316L SS substrates were textured using laser before application of BAG using sol-gel dip coating. Pull off test showed that the adhesion strength in case of textured and non-textured surfaces were 4.2 MPa and 2.46 MPa, respectively. This implies that texturing of the surface is helpful in increasing the adhesion strength of the coating. The bioactive glass-coated textured surface of 316L SS substrate showed better corrosion resistance in SBF than the bare substrate for which the respective corrosion current densities were 35 nA/cm2 and 353 nA/cm2, thereby indicating that the single layer sol-gel dip coating of bioactive glass improved the corrosion resistance of the 316L SS implants. The analysis of scanning electron microscopy (SEM) images of the coating after immersion in SBF shows the formation and growth of the apatite layer that will further inhibit the corrosion of the substrate. These results demonstrate the potential of the synthesized BAG as a coating material for 316L SS implants.