Effect Of New Corrosion Inhibitor On Corrosion Resistance Of Reinforced Concrete Structures In Stray Current Environment

Today,with the rapid development of industry and urbanization,the rail transit is particularly important.However,in the operation of metro or light rail,the stray current will inevitably be generated by DC power supply.Corrosion is the main cause failure reinforced concrete.However,the existence of stray current will not only accelerate the corrosion process,but also directly damage the concrete structure and reduce its service life.At present,the solution to stray current is basically the combination of"prevention"and"drainage".That is,to minimize the discharge of stray current at the source and to collect or evacuate it by drainage method.In addition,the use of steel corrosion inhibitor is also one of the effective ways to protect concrete structures.The corrosion inhibitor can restrain the anode and cathodic reactions by changing the surface state of steel bars,i.e.by restraining the anode and cathodic reactions.The dissolution of Fe²⁺and the avoidance of the direct contact of harmful substances such as O₂ with iron matrix can form a hydrophobic film in the pore when some alkanolamine organic rust inhibitors are mixed in the process of concrete manufacture,which can increase the compactness of the concrete and reduce harmful substances reaching the surface of steel bar through water,so as to inhibit the corrosion of steel bar.Previously,the research on rust inhibitors has played a relatively single role.Therefore,this topic is mainly committed to get an environmental protection rust inhibitor which can not only avoid corrosion of steel bars under stray current and chloride salt environment,but also increase the strength of the concrete structure.In view of the above background,this paper mainly carries out three parts of research.The first part is about the electrochemical behavior of reinforcing bar specimens in concrete simulation solution under chloride environment.Orthogonal experiments are set up to explore the optimum proportion of corrosion inhibitors with diethanolamine,sodium dodecyl sulfonate and sodium tetraborate as the main components by electrochemical testing methods,and they are separately single component under the same environment.Compared with the traditional rust inhibitor,the results show that the optimum ratio of the new rust inhibitor is 300 mg/L of sodium dodecyl sulfonate,30 mL/L of diethanolamine and 500 mg/L of sodium tetraborate.Compared with the single component and traditional rust inhibitor,the rust inhibition efficiency of the new rust inhibitor is 20-30%higher,up to 95%.The second part is the electrochemical conduction of the steel bar specimens in concrete simulation solution simulated by simulated stray current environment in laboratory.In order to influence the corrosion resistance of the new type of rust inhibitor under the combined action of stray current and chloride salt,a comparative test was set up.The results show that stray DC current is applied to saturated Ca?OH?₂ with 3.5%wt.NaCl.After 12 hours of electrification,the corrosion of steel bar is obvious,and the corrosion current density increases significantly.The pitting potential of the new type of rust inhibitor decreases,the Tafel slope of anode and cathode decreases from the polarization curve.The corrosion current density and pitting potential of the new type of corrosion inhibitor are obviously small than those of the blank group,and the corrosion phenomenon does not occur at the macro level,and lasts for 24 hours.The third part is the effect of the new type of corrosion inhibitor on the compactness of reinforced concrete,and the stray current is applied.The chloride diffusion coefficient is measured by RCM method.The results show that the diffusion rate of chloride ion to concrete increases obviously under stray current environment,and the electric flux of concrete blocks reaches 5778.67C after stray current is applied.The diffusion coefficient of chloride ion decreases by 45.62%after adding rust inhibitor,and the ability of concrete to resist chloride ion penetration increases obviously.The strength test of concrete specimens under 20V stray current shows that the compressive strength and flexural strength of concrete specimens decreased by34.14%and 12.5%respectively after 48h of 20V stray current action,and the compressive strength and flexural strength of a group of concrete specimens added with rust inhibitor decreased by 23.73%and 9.23%respectively,indicating that the addition of rust inhibitor can significantly inhibit the stray strength of concrete specimens.Adverse effects of divergent current on concrete strength.