Insights into the corrosion mechanism and electrochemical properties of the rust layer evolution for weathering steel with various Cl-deposition in the simulated atmosphere

Abstract

This study aims to make clear the effect of various Cl- deposition conditions on the changes of corrosion mechanism and electrochemical properties of the rust layer for weathering steel. The results indicate that the corrosion rate in presence of low Cl- deposition is divided into three stages: sharp increase stage, rapid decrease stage and tending to be stable stage. While, the high Cl- deposition process is divided into two stages: sharp increase stage and decrease stage. The increased of Cl- deposition increase the contents of the γ-FeOOH and β-FeOOH and decrease the contents of the α-FeOOH, and then to reduce the corrosion resistance. For the initial corrosion cycles, the increased of Cl- deposition influence the oxygen supply, resulting in spatial heterogeneity of the potential distribution to promote the corrosion reaction. As the prolonged corrosion cycles, the weathering steel of low Cl- deposition forms a protective rust layer to make the potential distribution become relatively uniform to reduce the corrosion rate, while the weathering steel of high Cl- deposition of the potential distribution is more unevenly distributed with distinct low and high potential zones to promote corrosion reaction.