The permanganate conversion coating on AZ91D magnesium alloy was prepared in a nitric acid-permanganate solution

and the corrosion resistant of the coating was examined by neutral salt spray testing（NSS） and polarization curves

and the adhesive forces of the conversion coating to organic coating were measured by lattice method. Meanwhile

the microstructure

constituent

structure and forming mechanism of the conversion coating were determined by SEM （scanning electron microscope）

EDS and XRD. It is found that the desirable corrosion resistance of the conversion coating that exhibits yellow and appears as cluster particles like deposits and is composed of Mn oxide can be observed at temperature of 40 ℃ for 120 s in 3.5 g/L KMnO4 solution with pH value of 4.0

which is greatly superior to that of the magnesium alloy substrate. In addition

the adhesive grade to iron red paint reaches up to 3B.