The Corrosion Inhibition Effect And Mechanisms Of Hydrophobic Functional Organic Corrosion Inhibitor

Admixed organic corrosion inhibitor is one of the most effective methods to improve the corrosion resistance and durability of reinforced concrete.However,the traditional admixed organic corrosion inhibitor can only improve the corrosion resistance of the embedded reinforcement,and its optimization effect on the pore structure and impermeability of concrete is very limited;the traditional admixed organic corrosion inhibitor might even exhibit negative effects on concrete.Hydrophobic functional organic corrosion inhibitors have both multi-site adsorption group and strong hydrophobic group,not only increasing the corrosion resistance of the reinforcement,but also improving the pore structure of concrete and enhancing the hydrophobicity of pore wall.It can effectively improve the durability of reinforced concrete in severe marine environment.In order to clarify the corrosion inhibition effect and mechanisms of hydrophobic functional organic corrosion inhibitor,the adsorption behavior of hydrophobic functional organic corrosion inhibitor and its influence on the corrosion performance of the reinforcement was investigated in this study.In addition,this paper further discusses the effect of hydrophobic functional organic corrosion inhibitor on the pore structure and hydrophobicity of cement paste,as well as impermeability and durability of concrete.The main results of this study are summarized as follows:（1）Hydrophobic functional organic corrosion inhibitors were hydrolyzed into two parts in simulated concrete pore solution:multi-site adsorption components containing C=O,O-H and strong hydrophobic components containing-COO,C-H and other hydrophobic groups.The multi-site adsorption components were dissolved in simulated concrete pore solution and adsorbed on the surface of the steel bar;the strong hydrophobic components reacted with Ca²⁺in simulated concrete pore solution and formed insoluble fatty acid calcium precipitates.（2）In the simulated concrete pore solution,the hydrophobic functional organic corrosion inhibitors were effectively adsorbed on the surface of the steel bar,and the adsorption amount was related to the concentration of inhibitors.The higher concentration of inhibitors was related to the larger adsorption amount and better corrosion inhibition effect.Before corrosion initiation of the reinforcement（during the first 7 days of immersion）,the hydrophobic functional organic corrosion inhibitor showed very fast adsorption rate.After efficiently adsorbed on the reinforcement surface,the hydrophobic functional organic corrosion inhibitor increased the critical chloride concentration and resulted in the positive open circuit potential shift of the reinforcement.As a result,the corrosion initiation of the reinforcement was delayed by the hydrophobic functional organic corrosion inhibitor.After corrosion initiation of the reinforcement,the inhibitor was continuously adsorbed on the reinforcement surface,although its adsorption rate was reduced.The hydrophobic functional organic corrosion inhibitor reduced the corrosion rate of the reinforcement and was beneficial for the formation of denser corrosion products（α-Fe₂O₃）,halting further corrosion damage of the reinforcement.（3）The hydrophobic functional organic corrosion inhibitors retarded the hydration process of cement paste and consumed calcium hydroxide to form insoluble fatty acid calcium which filled the pores in hardened cement paste.The hydrophobic functional organic corrosion inhibitors exhibited both pore blocking effect and hydrophobic effect in cement paste.On one hand,the inhibitors improved the pore structure of hardened cement paste by reducing the pore diameter,porosity（reduced by 5.0%～13.7%）and the amount of the harmful pores;on the other hand,the inhibitors increased the water contact angle on the surface of hardened cement paste（increased by about 3-4 times）and reduced the capillary water absorption rate and capillary water absorption amount of hardened cement slurry（reduced by 24.3%～48.6%）.（4）In reinforced concrete,hydrophobic functional organic corrosion inhibitors still exhibited significant corrosion inhibition effect and hydrophobic effect.After the inhibitors were admixed in concrete,the open circuit potential of the reinforcement embedded in concrete was positively shifted（more than 200 m V）;the impedance increased for more than 5 times,indicating that the corrosion resistance of the steel bar was greatly enhanced.In addition,the hydrophobicity of concrete was effectively increased by the hydrophobic functional organic corrosion inhibitors（when the dosage of corrosion inhibitor was 4 wt.%,the average water contact angle of concrete increased about 38.9°）,and the water absorption rate of concrete was reduced by 54.2%～64.3%,indicating that the hydrophobic functional organic corrosion inhibitors significantly improved the impermeability of concrete.In addition,the hydrophobic functional organic corrosion inhibitors also significantly retarded the penetration of chlorides in concrete,reduced the penetration depth of chlorides（reduced by 57.8%～76.1%）and chloride concentration in concrete（reduced by 58.9%when the content of corrosion inhibitors was 4 wt.%）.Therefore,the hydrophobic functional organic corrosion inhibitor can obviously improve the corrosion resistance of reinforced concrete.