Corrosion inhibition of hydrophobic coatings fabricated by micro-arc oxidation on an extruded Mg-5Sn-1Zn alloy substrate

A hydrophobic surface has been prepared on the surface of an extruded Mg-5Sn-1Zn (TZ51) alloy by micro-arc oxidation (MAO) with a subsequent stearic acid (SA) modification. The maximum water contact angle of 122.5° can be obtained by the MAO at 400V for 5min with the SA modification, which can be attributed to the rough island-structures and volcano-like structures with the formation of the SA coating. Both the hydrophobic surface and MAO coating effectively inhibit the corrosion of the extruded TZ51 alloy. The corrosion current decreases from 8.9 μA cm−2 to 0.07 μA cm−2 and the polarization resistance increases from 2.11 to 434.30 11 kΩ cm2 without changing corrosion potential (−1.53 V (vs. SCE)) after MAO at 400V for 5min MAO with subsequent SA treatment, indicating the effective corrosion inhibition of hydrophobic surface and the MAO coating. Main results obtained will shed some light on hydrophobicity of a new type of Mg-Sn-Zn system, which is critical to the exploration of new Mg alloys with strong corrosion resistance for potential applications in biomaterials or industrial fields.