Surface Modification of Stainless Steel 316L by Electrophoretic Deposition of Hydroxyapatite for Enhanced Biocompatibility

Stainless Steel 316L (SS316L) was coated with hydroxyapatite (HA) by electrophoretic deposition method. The uncoated and two coated samples (at 20 V for 20 min, and 30 V for 30 min) were compared to investigate the coating effect on hardness, corrosion resistance, and biocompatibility. The microstructures of uncoated and HA-coated samples were evaluated by scanning electron microscope (SEM) and energy dispersive X-ray diffraction (EDX). Scratch test and micro Vickers hardness test were used to evaluate the adhesion and hardness of HA-coated samples. The electrochemical and in vitro biocompatibility analyses were carried out using Potentiostat and Cytotoxicity Assay. Cross-sectional SEM images showed uniform, homogenous, and crack-free HA coating on SS316L with a thickness of 45 μm at 20 V and 55 μm at 30 V. EDX analysis revealed the presence of calcium, phosphorous, and oxygen elements in the coated SS316L surface. The average surface hardness was 245 HV and 289 HV for coated samples at 20 and 30 V respectively. The scratch test showed better adhesive strength of coating, and electrochemical testing in Ringer Lactate solution showed improved corrosion resistance for the coated sample at 30 V as compared to 20 V and the uncoated sample. The cytotoxicity assay confirmed improved cell viability and growth on SS316L samples coated with HA at 30 V as compared to 20 V and uncoated samples. SS316L with HA coating at 30 V, with its better mechanical properties, low corrosion resistance, and good biocompatibility, represents a potential biomaterial candidate for biomedical applications.