A reinforced organic-inorganic layer generated on surface of aluminium alloy by hybrid inhibitors

The anticorrosion performance of inhibitors for 7003 aluminium alloy in 2 wt.% NaCl aqueous solution at pH 6.5 by sodium gluconate (SG), sodium dodecyl sulfate (SDS), NaNO3 and their mixture was investigated using polarization tests, electrochemical impedance spectroscopy measurements, Fourier transform infrared spectroscopy, X-ray diffraction as well as scanning electronic microscopy. The results show that hybrid inhibitors reduce the polarization currents, both in cathodic reaction and in anodic reaction, by around one order of magnitude as compared with mono-inhibitor. A porous oxide layer is formed on surface of Al alloy by NaNO3, and then pores are blocked by physical adsorption of SDS, which is subsequently reinforced by the precipitation of SG complex enriched with AlOC6H11O7 bonds. The above three parts are integrated into a complex passive layer to protect Al alloy.