Research On Impressed Current Cathodic Protection Method Of Bridge Cable Structure

Cables and hangers of bridge(inclined cables,slings,and booms)are one of the main load-bearing members of cable-structured bridges.They are not only affected by the weight of the bridge and moving loads,but also by environmental factors such as temperature,humidity,and ultraviolet light.It is easy to be corroded in the corrosive environment of heavy acid rain area,and the anchoring area under the sling is often the most corroded part.This article relies on the National Natural Science Foundation of China project "Research on the Corrosion Fatigue Damage Mechanism and Life Prediction Model of Cable Stays under the Coupling of Alternating Loads and Erosion Environment(No.51478071)" project and the National Key R & D Program topic "Urban Expressway Bridge Exceeding Limit Loads Monitoring and early warning system and safety risk control technology(No.2017YFC0806001)",conducted a cathodic protection test study on the impressed current of the cable wire,and aimed at the lower anchor head and steel wire with more diseases in the cable anchoring system,on the basis of the traditional protection measures(epoxy coating,pure galvanized layer,zinc alloy coating,etc.),a new anticorrosion method of impressed current cathodic protection is proposed.The main research work and conclusions are as follows:Firstly,this paper summarizes and analyzes the principle of impressed current cathodic protection technology for the cable wire.Understand the corrosion of galvanized steel wire in different environments and the development process of corrosion.Through the control of electrochemical corrosion-polarization,the mechanism of cathodic protection is explained.On the basis of the protective measures,a new idea of applying external current combined cathodic protection to the steel wire is proposed.Secondly,a method of impressed current cathodic protection for the cable wire is proposed.Conducted a cathodic protection test of the impressed current of the steel wire in a chloride salt environment,and comparatively analyzed the color of the solution,the macro and micro appearance of the cable wire and the weightlessness change of the cable after the test.It was found that impressed current cathodic protection for the cable wire is effective,and impressed current cathodic protection can slow down or inhibit the corrosion of steel wire.Thirdly,the effect of impressed current cathodic protection for cable steel wire is studied.Conducted a cathodic protection test study on the impressed current of the steel wire in an acid rain environment,and comparatively analyzed the appearance,weightlessness,and open circuit potential(corrosion potential)of the cable after the test.It was found that the cable wire corrosion rate is faster in p H=3 acid rain solution than5% Na Cl solution,and the cathodic protection of the impressed current can slow down the damage of the galvanized layer and inhibit the corrosion of the steel wire.As the test increases with time,the damage of the galvanized layer of the cable wire gradually deepens,and the cathodic protection effect of the sacrificial anode gradually weakens as the damage of the galvanized layer deepens,and the cathodic protection of the impressed current gradually increases.Fourthly,the experimental study determined the cathodic protection voltage range of the impressed current to the cable wire.The tensile test of the cable wire after the impressed current cathodic protection test was carried out,and the fracture shape after the tensile test was compared and analyzed to determine whether the test steel wire is prone to hydrogen embrittlement,thereby determining the protection voltage range of the cable wire in acid rain solution.Fifthly,the experimental study determined the cathodic protection voltage range of the impressed current to the bundle of cable wire.Conducted a cathodic protection test for the impressed current of the cable,comparatively analyzed the appearance and open circuit potential of the cable after the test,and found that the cathodic protection of the impressed current for the entire cable is effective,has great practical significance,and determine the protection voltage range of the entire cable in acid rain solution.Finally,the scheme of cathodic protection system with impressed current for the cable is proposed.Through the analysis of the cable structure and investigation data,it is found that the most serious corrosion of the cable is in the lower anchoring area,and the water accumulation in the lower anchoring area is one of the main causes of the corrosion of the cable in the anchoring section.Under the condition of water accumulation in the lower anchorage area,the cathodic anchorage system is designed with an external current cathodic protection scheme,which can not only solve the corrosion problem of the anchorage system,but also have a monitoring function to reliably monitor whether the anchorage system is in water.