Enhanced corrosion resistance and cellular behavior of ultrafine-grained biomedical NiTi alloy with a novel SrO-SiO2-TiO2 sol-gel coating

► A novel, homogeneous and smooth SrO-SiO2-TiO2 sol-gel coating without cracks was fabricated on ultrafine-grained NiTi surface. ► The sol-gel coating significantly increased the corrosion resistance and decreased the release of nickel ions of ultrafine-grained NiTi. ► Ultrafine-grained NiTi with sol-gel coating enhanced osteoblast-like cell attachment, spreading and proliferation.