Characterization of hydroxyapatite layer on AISI 316L stainless steel.

Bioactive coatings can be divided into two main groups - organic and inorganic coatings. Hydroxyapatite (HA) is well known as one of inorganic part of mammal's bone structure and is highly recommended for use in implantology. This paper is mainly focused on characterization of hydroxyapatite particles electrochemically deposited from water solution of Ca(NO3)2 and NH4H2PO4 on surface of AISI 316L (1.4404) stainless steel with different roughness profiles and surface treatment. The effect of surface roughness itself is discussed as well as heat treatment (400 {deg}C) of samples after coating deposition. Electrodeposition of HA was carried out at cycling of potential values of -2.0 V for 2 s and 0 V (NHE) for 1 s; 200 cycles was used for this study. Electrochemical properties of such treated samples were characterized using voltammetry and EIS methods. It was found, that time of deposition significantly changes electrochemical parameters of equivalent el. circuit used for closer characterization of coating properties but only marginally affects corrosion properties like open circuit potential (OCP), corrosion potential (Ecorr) or potential of passive layer breakdown (Ebreak). Pull-off test also proved significant correlation between surface roughness, heat treatment and adhesion of deposited coatings