Effect of current density on the cathodic protection efficiency and mechanical properties of pre-stressed high-strength steel wires for stay cable

Abstract

Stay cables are the main force-bearing structures of cable-stayed bridges, which are mainly composed of internal high-strength steel wires and external high-density polyethylene (HDPE) sheaths. When the external HDPE sheaths crack, the internal high-strength steel wires are severely corroded, thereby endangering the security of the whole bridge. The effects of pre-stress level and protection current density on the cathodic protection efficiency and mechanical properties of stay cable high-strength steel wires were investigated in this study on the basis of the impressed current cathodic protection (ICCP) method for stay cable high-strength steel wires in rainwater environment. The corrosion degree of steel wires was characterized qualitatively and quantitatively by observing the macro and micro morphologies of the corrosion specimen and the weight loss measurement. The ICCP efficiency was evaluated in terms of the variation of open circuit potential (OCP) and instant-off potential (IOP). Static tensile test was used to investigate the difference in the mechanical properties of steel wires with different corrosion degrees. Results showed that the corrosion rate of steel wires increased with pre-stress level, and the greater the pre-stress, the higher the corrosion probability of steel wires. The application of ICCP reduced the accumulation of rust on the surface of the steel wires and the number and size of corrosion pits. The ICCP efficiency increased with the protection current density. No significant difference was found in the IOP values of the steel wires with different pre-stress levels when the protection current density was constant. All the steel wires with ICCP in the later stage of the test were effectively protected and are not in the overprotected state.