Study On The Corrosion Behavior Of Carbon Steel And Environment-friendly Inhibitors In Simulated Concrete Solution Containing Chloride

The durability of reinforced concrete has an important influence on the service life of buildings as well as the life and property of people.Chloride ions erosion is an important factor that will influence the durability of the concrete structure.The application of inhibitors is a convenient and efficient method to control corrosion.Nowadays,the majority of inhibitors used in concrete environments are inorganic inhibitors which is highly toxic.Therefore,researches on corrosion behavior of concrete steel and low-toxicity green inhibitors are of great significance.The influence of chloride ions on corrosion behavior of concrete steel corrosion have been studied by means of electrochemical techniques and surface analysis techniques in simulated concrete pore solution?SCP solution?,laying foundation for further researches of inhibitors.The inhibition behaviors of sodium borate,zinc gluconate,sodium lignosulphonate and triethanolamine for Q235 carbon steel have been studied by means of potentiodynamic polarization curves,electrochemical impedance spectroscopy?EIS?and weight loss measurement.As for sodium lignosulphonate,which had high inhibiting efficiency and a bright prospect,the further study of its inhibition mechanism and adsorption on carbon steel is discussed in this report.The results of this paper are as follows:?1?The passivation behavior of concrete steel was suppressed in SCP solution which contains chloride.As the chloride ions concentration increased,the degree of passivation behavior and damage of the passivation film was also on the rise.The chloride threshold value for the pitting corrosion was 0.04 mol/L.?2?Four corrosion inhibitors possessed certain inhibitive effect on corrosion of carbon steel in SCP solution containing chloride.The inhibition effects of these four inhibitors,in the order of effectiveness,were sodium lignosulphonate,zinc gluconate,sodium borate,then triethanolamine.?3?Sodium lignosulphonate was a green inhibitor which could slow-release the erosion of the concrete effectively.When the addition of sodium lignosulphonate was 0.0015 mol/L,the pitting corrosion resistance of carbon steel can withstand maximum 0.2 mol/L chloride ions,while the inhibition efficiency was 95.8%in SCP solution containing 0.08 mol/L chloride ions.?4?Sodium lignosulphonate was an adsorption-type inhibitor.The spontaneous mixed absorption is basically chemical absorption,and the whole process is exothermic.The main thermodynamic parameters of adsorption reaction were:?G_m value was-36.4 kJ/mol,?H_m value was 45.2 kJ/mol,?S_m value was-21.78 J/mol.Sodium lignosulphonate molecule had more than one adsorption centre on the surface of carbon steel,and had both physical and chemical adsorption.The sodium lignosulphonate molecule had intramolecular synergic effects which can help to improve inhibition performance.?5?Sodium silicate could improve the inhibition performance of sodium lignosulphonate on carbon steel.The precipitation film formed by sodium silicate accelerated film forming speed of sodium lignosulphonate,which improved the compactness of the film.The inhibition efficiency reached 98.8%when 0.0005 mol/L sodium lignosulphonate and 0.0005 mol/L sodium silicate was added into SCP solution containing 0.08 mol/L chloride ions.