Effect of outer rust layer on cathodic protection and corrosion behavior of high-strength wire hangers with sheath crack in marine rainfall environment

Abstract

After the high-density polyethylene (HDPE) sheath crack, the hanger steel wires of large-span suspension bridge are prone to corrosion under the erosion of the marine rainfall environment. This study investigates the influence of the outer rust layer on the impressed current cathodic protection (ICCP) and the corrosion behavior of hanger steel wires. The corrosion morphology and corrosion products of the wire are analyzed by SEM and XRD. The result shows that in the simulated marine rainfall environment, both ICCP and removal of the outer rust layer can reduce the corrosion rate of hanger steel wires. Especially the removal of the outer rust layer can significantly improve the cathodic protection efficiency. Removing the initial outer rust layer on the surface before applying ICCP is a benefit for forming a complete and dense corrosion product layer. In addition, it contributes to the generation of Zn5(OH)8Cl2H2O and Al2O3 with stable structures in the corrosion products. These corrosion products benefit to forming a passivation film, which helps isolate the iron matrix from harmful substances.