Improved Corrosion Behavior of Biodegradable Mg-4Zn-1Mn Alloy Modified by Sr/F co-doped CaP Micro-arc Oxidation Coatings

The Sr/F co-doped CaP (Sr/F-CaP) coatings were prepared by micro-arc oxidation (MAO) under different voltages to modify the microstructure and corrosion behavior of Mg-4Zn-1Mn alloy. The surface and interface characteristics investigated using scanning electron microscopy (SEM) and energy dispersive X-ray spectrometer (EDS) showed that the MAO coatings displayed uneven crater-like holes and tiny cracks under lower voltage, while they exhibited relatively homogeneous crater-like holes without cracks under higher voltage. The thickness of MAO coatings increased with increasing voltage. The corrosion behavior of Mg-4Zn-1Mn alloy was improved by the MAO coatings. The MAO coatings prepared under 450 V and 500 V voltages possessed the best corrosion resistance with regard to the electrochemical corrosion tests and immersion corrosion tests, respectively. The MAO coatings fabricated under 450-500 V could provide a better corrosion protection effect for the substrate.