Evolution of corrosion of MnCuP weathering steel submitted to wet/dry cyclic tests in a simulated coastal atmosphere

The evolution of rust on MnCuP weathering steel submitted to a simulated coastal atmosphere was investigated by corrosion weight gain, scanning electron microscopy, X-ray diffraction, and electrochemical methods. The results indicate that the higher corrosion rate during the first stage than that during the second stage is related closely to the rust composition and electrochemical properties. The corrosion rate evolution is caused by the formation of a protective rust layer with a higher relative amount of α-FeOOH. The rust initially enhances and then stabilizes the cathodic process, but the anodic process tends to be inhibited by the protective rust layer.

► The evolution of rust on MnCuP weathering steel submitted to a simulated coastal atmosphere has been investigated.
► The corrosion evolution of MnCuP weathering steel can be divided into two stages with distinct rust properties.
► A protective rust layer with higher amounts of α-FeOOH and lower Fe3O4 forms as the corrosion proceeds.
► The rust initially enhances and then stabilizes the cathodic process, but the anodic process tends to be inhibited.