Synthesis and characterization of modified iron oxide hydrophobic corrosion-resistant pigment for aluminum alloy coating

A hydrophobic coating containing modified iron oxides was prepared for corrosion protection of aluminum alloy. The modified iron oxide particles were synthesized using the annealing method and the evaluation of the corrosion-resistant benefits of modified iron oxides as additive in the epoxy resin coating was conducted. The raw FeOOH phase can be transformed into the α-Fe2O3 phase by increasing the annealing temperature. The morphology, colors, and pore size of the modified iron oxide are controllably evolved via finely adjusting the annealing temperature, which is beneficial for the compatibility, dispersion, and stability with epoxy resin. Besides, modified α-Fe2O3 annealed at 700 °C exhibited elliptical morphology and good solubility in epoxy resin solvents to form a hydrophobic corrosion inhibition layer (TP700), which further improves the corrosion resistance. Findings of corrosion electrochemical measurements and salt spray test confirmed the existence of TP700 composite coating resulted in the best corrosion protective properties on aluminum alloy during the corrosion process with the minimum corrosion current of 7.75 × 10−10 A cm−2 and the maximum |Z|0.01Hz value of 1.80 × 108 Ω cm2, which both are about two orders of magnitude higher than the commercial Fe2O3. Our results suggest a new venue for preparing modified iron oxide pigment on the surface of aluminum alloy materials for enhanced anti-corrosion applications.