Biomimetic deposition process of an apatite coating on NiTi shape memory alloy

Biomimetic deposition process of an apatite coating on NiTi shape memory alloy (SMA) after it was pretreated with 30% H2O2 solution and subsequently 1 M NaOH solution was studied using a simulated body fluid (SBF) soaking test. Biomimetic nucleation of apatite on the chemically pretreated NiTi SMA has a short induction period down to 6 h. With longer soaking time, more apatite appeared on the NiTi substrate but our control experiments did not reveal any apatite formation on the chemically polished NiTi SMA. After immersion in SBF for 48 h, the chemically pretreated NiTi SMA was fully covered with a dense hydroxyapatite coating. The biomimetic deposition of the apatite coating was attributed to the catalytic effect of abundant Ti–OH groups and Na2TiO3 on the surface of the chemically pretreated NiTi SMA.