EFFECT OF KOH ON MICRO-ARC OXIDATION COATINGS OF 2A12 ALUMINUM ALLOYS IN CH3COONa–Na2WO4 ELECTROLYTE
The ceramic coatings were prepared on 2A12 alloy by micro-arc oxidation in CH 3 COONa – Na 2 WO 4 electrolyte system with different concentration of KOH added. The effects of KOH in this electrolyte on micromorphology, phase compositions, adhesion and corrosion resistance of the coatings were investigated by scanning electron microscope (SEM), X-ray diffraction (XRD), scratch test and electrochemistry workstation. The results show that KOH has a significant influence on the surface morphology, which can make the surface smoother. The adhesion of the coating becomes stronger with the increase of KOH in the electrolyte. The corrosion resistance of the coated specimen increases a lot compared with that of the substrate. And the lowest corrosion current density (I corr ) of the coating prepared in the electrolyte with KOH is about three orders of magnitude lower than that of the substrate.