Study on influence of native oxide and corrosion products on atmospheric corrosion of pure Al

• Corrosion products layer is only formed in coastal atmosphere.
• In coastal atmosphere, rate controlling step is diffusion process.
• In rural atmosphere, rate controlling step is charge transfer process.
• Pitting area increases greatly in coastal site, but slightly in rural site.

Effects of native oxide and corrosion products on atmospheric corrosion of aluminium in rural and coastal sites were studied by electrochemical impedance spectroscopy (EIS), open-circuit potential (OCP) and scanning electron microscope (SEM) techniques after outdoor exposure. In the rural atmosphere, only the compact, adhesive native oxide layer exists, and the rate controlling step is diffusion process, while in the coastal atmosphere, another loose, inadhesive corrosion products layer exists, and a charge transfer process controls the corrosion process. The pitting area in the coastal atmosphere increases over time more obviously than that in the rural atmosphere.