Organic thin films on magnesium alloys could serve as a protection layer for controlled biodegradation and for subsequent tailored modification. In this report we demonstrate the preliminary invitro stability of octadecylphosphonic acid (ODPA) organic thin films on Magnesium (Mg) alloy using impedance spectroscopy. Impedance spectroscopy of Mg alloy before and after coating with ODPA organic thin films determined the surface corrosion resistance after film deposition.