LAUSR

Abstract The black micro-arc oxidation (MAO) thermal control coating was prepared in the electrolyte containing Na3PO4, K3[Fe(C2O4)3], C6H11KO7 and NaOH. The complexion mechanism of iron(III) complexes was studied. The effect of adding K3[Fe(C2O4)3] on electrolyte and MAO coating morphology, element composition, phase composition and thermal control properties were investigated. The results showed that K3[Fe(C2O4)3] hydrolysis to produce Fe(OH)3 colloidal particles that negatively charged, gluconate and oxalate complexing with iron(III). Discharge channels and molten oxides particles in bigger size were discovered in the MAO coating prepared in the electrolyte containing K3[Fe(C2O4)3]. Fe2O3 and Fe3O4 were found in the MAO coating surface prepared in the electrolyte with K3[Fe(C2O4)3] and the content of Fe in the outer layer was higher than that in the inner layer. The addition of K3[Fe(C2O4)3] could significantly improve the thermal control property of the MAO coating, and make it black. Graphical Abstract