Atmospheric corrosion monitoring of a weathering steel under an electrolyte film in cyclic wet–dry condition

• The corrosion evolution of a steel under an electrolyte film was investigated.
• The rust layer greatly affects the corrosion evolution process of the steel.
• The corrosion rate varies greatly during different corrosion periods.
• A corrosion evolution model has been proposed.

Electrochemical Impedance Spectroscopy (EIS) and film thickness measurements have been employed to study the corrosion monitoring of steel under an electrolyte film in wet–dry cycles simulating a coastal atmosphere. The results indicate that within each cycle, the corrosion rate increases during drying process due to an increase in Cl− concentration and an enhancement of oxygen diffusion by thinning out of the electrolyte. As corrosion process proceeds, the corrosion rate increases greatly and reaches a maximum. During subsequent corrosion stage, the corrosion rate decreases greatly and keeps at a low value due to the formation of a stable rust layer.