In this study, a Ti6Al4V alloy surface commonly used in the human body for load-bearing prostheses was modified by micro arc oxidation (MAO) to produce magnesium (Mg)-integrated titanium oxide with varying Mg contents, the presence of which is known to promote bone formation and proliferation in the physiological environment. The in vitro biological responses of these coatings were studied in simulated body fluid (SBF) at 37 degrees C for 6 weeks. The structural changes of the coatings, changes in pH and changes in the concentrations of Ca, Mg and P ions in OF, as determined by inductively coupled plasma (ICP), were monitored at regular intervals. The Tafel polarization technique was used to analyse the solubility properties of the coatings to explain the relation between the Mg concentration of the coatings and the coatings' bioactivity properties. It can be concluded that the presence of Mg in oxide films formed by MAO accelerates dissolution-precipitation reactions and enhances the bioactivity of the films during the early stages of implantation. (C) 2015 Elsevier B.V. All rights reserved.