The effect of the icosahedral phase on the growth behavior of the thin oxide film coated on MgZn12Y1.7 alloy sample by micro arc oxidation (MAO) was studied. During MAO coating in a phosphate electrolyte with a current density of 25 mA/cm(2), the responding voltage of the present sample gradually increased as the coating time increased up to 80 s. The surface structure observations indicated that the thin oxide film was prone to be formed more easily on the top of the icosahedral phase than on that of the alpha-Mg phase matrix in the MgZn12Y1.7 alloy sample. This implies that the growth rates of the thin oxide films were different and were also enhanced on the icosahedral phase, which could be explained by the low electrical conductivity of the icosahedral phase itself leading to appreciable micro arcs during MAO coating. (C) 2013 Elsevier B.V. All rights reserved.