Effect of cathodic protection current density on corrosion rate of high-strength steel wires for stay cable in simulated dynamic marine atmospheric rainwater

Abstract

Impressed current cathodic protection (ICCP) is considered an effective method for reducing the corrosion of structures, but is seldom used in the corrosion protection of high-strength steel wires for bridge cables (e.g., stay cable) because the atmospheric environment in which the steel wires are located can barely provide electrolyte solutions for the ICCP system. However, rainwater accumulates on the cable surface and forms rivulets under rainfall conditions, and such rainwater rivulets can be used as electrolyte solutions for the ICCP system of high-strength steel wires. On this basis, this study proposed an ICCP method for high-strength steel wires in rainfall environment and investigated the effects of different protection current densities on the corrosion rate of stay cable steel wires in a simulated dynamic rainwater environment. In this work, the test time and environmental temperature were fixed at 20 d and 28 °C, and a 3% NaCl solution was employed as the simulated rainwater. Corrosion morphologies of steel wires were used to qualitatively characterize the corrosion degree. Weight loss and electrochemical measurements were used to quantitatively characterize the corrosion rate. Scanning electron microscopy and X-ray diffraction were used to analyze the microscopic morphology of corroded steel wires and the chemical composition of corrosion products, respectively. Results showed that in comparison with unprotected steel wires, the surface of steel wires with ICCP were flatter, the number and size of corrosion pits were significantly reduced, and the corrosion rate was significantly reduced. Thus, ICCP played a protective effect throughout the test period; however, the protection efficiency was slightly different under different flow rates. The steel wires were effectively protected at any protective current density under the flow rate of 0.7 mL/min, but were not effectively protected when the protection current density reached 60 mA/m2 under the flow rates of 7 mL/min and 14 mL/min.