Corrosion inhibition performance of polypyrrole Al flake composite coatings for Al alloys

Polypyrrole (PPy) was deposited on Al flakes in the presence of oxyanions (molybdate, phosphate or vanadate) as inhibiting dopants and the PPy modified Al flakes were incorporated into an epoxy primer as protection pigments for AA 2024-T3. The protection performance of the PPy Al flake coating was assessed by electrochemical evaluations including Scanning Vibrating Electrode Technique (SVET), Electrochemical Impedance Spectroscopy (EIS) and salt spray test. The oxyanion doped PPy Al flake coating shows enhanced protection performance for AA 2024-T3. An oxygen scavenger protection mechanism is suggested for PPy in the composite coating, and the roles of Al flake and oxyanions in the formulation are discussed.

► Oxyanion incorporation enhances protection property of the PPy Al flake coatings.
► An oxygen scavenger protection mechanism is proposed for PPy in composite coatings.
► Al flake improves dispersion of PPy in the composite coating.
► Vanadate as inhibiting dopant in the composite coating shows good performance.