Brushite/hydroxyapatite Coatings on H2SO4 Passivated 316LSS by Electrodeposition: in Vitro Corrosion and Anti-Inflammatory Activity

This study evaluated the corrosion behavior and anti-inflammatory activity of brushite (BS or DCPD, CaHPO4·H2O)/hydroxyapatite (HAp, Ca10(PO4)6(OH)2) coating on sulfuric acid (H2SO4) treated 316L stainless steel (SS). The coating was applied using the electrodeposition process on untreated and H2SO4 passivated 316L SS surface. The obtained samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy (EDS) to obtain crystal and electronic structure as well as morphological and compositional information of the coated 316L SS. Electrochemical impedance spectroscopy (EIS) tests were performed in 0.9 % sodium chloride (NaCl) solution and compared with the pristine (P316L), H2SO4 treated (T316L), untreated/BS/HAp coated (BHP316L) and treated/BS/HAp coated (BHT316L) 316L SS specimens. The anti-inflammatory activity was carried out for the coated samples by the protein denaturation method. The results showed that the BS/HAp coating on H2SO4 treated 316L SS (hereafter, denoted as BHT316L) were susceptible to corrosion attack against 0.9 % NaCl solution. Additionally, the anti-inflammatory activity of the BHT316L was found to be lower compared to control (sodium diclofenac), indicating that particular concern should be given to H2SO4 treated 316L SS as the corrosion products formed by this surface modification may cause harmful effects in the human physiological environment.