Influence of 8-hydroxyquinoline on properties of anodic coatings obtained by micro arc oxidation on AZ91 magnesium alloys

The influence of 8-hydroxyquinoline (8-HQ) on formation and properties of anodic coatings obtained by micro arc oxidation (MAO) on AZ91 magnesium alloys was studied by scanning electron microscope (SEM), energy dispersive spectrometry (EDS), Fourier transform infrared (FT-IR) spectroscopy and potentiodynamic polarization tests. The results demonstrate that 8-HQ can decrease the solution conductivity, take part in the coating formation and change the coating color. By developing anodic coatings with increasing thickness, insoluble Mg(HQ)2 and small pore size, 8-HQ improves the corrosion resistance of the anodized magnesium alloys. The coating shows the best corrosion resistance in the solution of 10 g/L NaOH and 18 g/L Na2SiO3 with 2 g/L 8-HQ.

► 8-HQ can promote the coating formation and change the coating color.
► 8-HQ can increase the coating thickness and decrease the pore size.
► Insoluble Mg(HQ)2 is formed in anodic coatings in an alkaline solution with 8-HQ.
► 8-HQ improves the corrosion resistance of the anodized magnesium alloys.