Sandwiched polydopamine (PDA) layer for titanium dioxide (TiO 2 ) coating on magnesium to enhance corrosion protection

•A polydopamine (PDA) layer was inserted into TiO2 coated Mg.•The sandwiched PDA/TiO2 coated Mg achieved significantly low corrosion current density icorr.•The sandwiched PDA/TiO2 coated Mg exhibited remarkably suppressed in vitro degradation rate.•The sandwiched PDA hinders effectively the electrical pathway of galvanic corrosion cell.•Such kinetic strategy promises a new route for corrosion-control of extremely active magnesium.