Synergistic effect of V and Mn oxyanions for the corrosion protection of anodized aerospace aluminum alloy

• Successfully incorporated Mn–V oxyanions into anodized layer developed on AA2024.
• Post treatment of anodized layer had resulted in effective sealing of pores/cracks.
• EIS results showed self-healing behavior of MnVO sealed oxide layer.
• MnVO filled oxide layer passed about 2000 h of salt spray exposure.

In the present study sulphuric acid anodized oxide layer was sealed with permanganate (MnO) and permanganate–vanadate (MnVO) ions. The effect of the incorporation of these oxyanions on the corrosion performance of plain oxide layer (PO) was investigated by various characterization techniques such as field emission scanning electron microscopy (FESEM), energy dispersive X-ray analysis (EDAX), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The barrier layer resistance value of plain oxide layer was increased about 13 times due to the incorporation of mixed Mn–V oxyanions. The damage function (D) calculations revealed the self-healing mechanism of MnVO. The potentiodynamic polarization results showed higher corrosion inhibition performance of MnVO compared to that of MnO even after 336 h of immersion in 3.5% (0.6 M) NaCl solution. No sign of visible corrosion products were observed on MnVO surface even after 2000 h of continuous salt spray exposure.