An Al2O3/MgO composite coating was synthesized on magnesium alloy AZ33 using a chemical conversion process for the first time. EDTA-2Na was introduced in the Al conversion solution to chelate Al3+, and involved Al3+ in the cogrowth reaction. Inductively coupled plasma mass spectrometry and x-ray diffraction results showed that the coating consisted of Al2O3 and MgO with the ratio of 1:6. Visual and cross-sectional analysis revealed that the coating was compact and flat after heat-treatment. The polarization resistance (Rp) of the coated alloy was about three orders of magnitude higher than that of the untreated alloy in 3.5 wt% aqueous NaCl solution. The coated alloy still maintained high corrosion resistance after 72 h immersion in the solution. It is believed that this effective and low-cost method can provide a new coating for the protection of magnesium alloys.

Subject
X-ray diffraction, Electrochemical impedance spectroscopy, Coatings, Substrates, Magnesium alloys, Surface morphology, Surfaces, Sodium chloride solution, Composites, Immersion, Corrosion resistance, Chemical conversion coatings, Samples
Keywords:
chemical conversion coating, corrosion resistance, magnesium
© 2019, NACE International
2019
You do not currently have access to this content.