Comparative investigation on corrosion resistance of MgF2 coated, PLA coated and composite coated biodegradable magnesium alloy wires for medical application

The fluorinated treatment coating (MgF2), polylactic acid (PLA) coating, and composite coating (MgF2/PLA) were prepared on biodegradable Mg-2.2Zn-0.3Ca alloy wires to improve the corrosion properties. The composition characteristics and microstructure of the samples were investigated by field emission scanning electron microscopy (FE -SEM), energy dispersive X-ray spectroscopy (EDS). The corrosion resistance of all samples were investigated by immersion tests and electrochemical techniques in vitro simulated body fluid (SBF). The results indicated single MgF2 and PLA coating performed opposite protective behaviors in the short and long term immersion tests. The corrosion rate of MgF2-coated samples was lower than that of PLA-coated samples, but the corrosion fracture lifetime of MgF2-coated samples was shorter than that of PLA-coated samples. The MgF2/PLA composite coating exhibited superior short and long term protective effect for Mg wires. These results exhibit that single MgF2 or PLA coating cannot behave strong anti -corrosion ability, only the MgF2/PLA-coated Mg2.2Zn-0.3Ca alloy wires has high corrosion resistance in vitro immersion, and it has promising potential for surgical implant applications.