The corrosion resistance, biocompatibility and biomineralization of the dicalcium phosphate dihydrate coating on the surface of the additively manufactured NiTi alloy

Selective laser melting (SLM)-fabricated NiTi alloys have attracted widespread interest because they can achieve high-precision preparation of implant materials with complex structures. However, as an implant material, SLM-NiTi alloy exhibits poor osteogenic and excessive release of Ni ions. In this investigation, a bioactive dicalcium phosphate dihydrate (DCPD) coating was prepared on the surface of SLM-NiTi alloy by electrodeposition for the first time to improve the biocompatibility and corrosion resistance of the SLM-NiTi alloys. The influence of coating preparation parameters (deposition current and deposition time) on morphology and corrosion resistance had been studied by SEM, electrochemical and immersion tests. The DCPD coating obtained when the deposition current was 3 mA and the deposition time was 30 min showed a uniform and dense morphology and had the best corrosion resistance, which the corrosion current density Icorr was three orders of magnitude lower than that of SLM-NiTi alloy. Moreover, as the precursor of hydroxyapatite (HA), DCPD effectively promoted the deposition of HA, thus improving the biomineralization property of the SLM-NiTi alloy. The in vitro cell experiments showed that the DCPD coating provided a good interface and microenvironment for the growth and adhesion of osteoblasts. Good corrosion resistance, biocompatibility and biomineralization properties render the DCPD coated SLM-NiTi alloys have great clinical application prospects as biomedical implants.