Corrosion resistance, in-vitro biodegradation and biological response of electrodeposited brushite/hydroxyapatite on H2SO4 treated 316L SS for orthopedic applications

Abstract

Abstract In this work, corrosion behaviour of brushite/hydroxyapatite (DCPD, CaHPO4·H2O; HA, Ca10(PO4)6(OH)2) coating on sulfuric acid (H2SO4) treated 316L stainless steel (SS) was evaluated through impedance studies. Calcium phosphate-based coatings (CaP) were nucleated and grown using electrodeposition process on 316L SS. The obtained samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy, with elemental analysis (SEM-EDS) in order to obtain microstructural, morphological and compositional information of the coated SS. Electrochemical impedance spectroscopy (EIS) tests were performed in 0.9% NaCl solution and compared with the pristine and HAp coated SS specimens. The anti-inflammatory activity was carried out for the coated samples by protein denaturation method. Crack-free deposition was observed by SEM results. Formation of primarily hydroxyapatite and an additional secondary phase, brushite, was confirmed by XRD and FT-IR techniques. EIS measurements of the brushite/hydroxyapatite coatings on H2SO4 treated 316L SS showed susceptibility to corrosion attack against the 0.9% NaCl solution. Added to this, anti-inflammatory activity revealed the metallic oxides present on H2SO4 treated 316L SS surface with HAp electrodeposited layer (hereafter, denoted as HAp/1-H2SO4) increased protein denaturation, exhibiting inflammatory response. These results demonstrated that particular concern should be given to H2SO4 treated 316L SS, as the corrosion products formed by this surface modification may cause deleterious effects when exposed to the human physiological environment.