Study of rust layer evolution in Q345 weathering steel utilizing electric resistance probes

In this study, a corrosion-monitoring sensor was used to investigate the evolution mechanism of rust formation on Q345 weathering steel. The results indicate that rust layer formation proceeded through alternating thickening and conversion (no thickening) stages. Specifically, the transformation of Fe2+ to gamma-FeOOH increased the thickness of the rust layer in the thickening stages. After each thickening stage, conversion occurred: the composition of the rust layer changed, which entailed an increase in the alpha-FeOOH content. In the stage of conversion, no thickening occurred and this process was the controlling step of weathering steel rust stabilization.