Effects Of Two Kinds Of Corrosion Inhibitors And Their Compounding On The Corrosion Behavior Of Carbon Steel In Different Simulated Concrete Pore Solutions

The armoured concrete is a kind of commonly used engineering material, in order to prevent corrosion, we need to join the corrosion inhibitor to prevent corrosion in it.Nitrite is widely used for corrosion inhibitor in the field of concrete. Because there is NaHCO₃ in concrete pore fluid, so NaNO₂ is important in the concrete pore fluid containing NaHCO₃ or not containing NaHCO₃ for the corrosion of Q235 carbon steel.In addition, D-glucose acid sodium is a kind of green corrosion inhibitors, if D-glucose acid sodi?m nitrite with NaNO₂ formating a composite inhibitor, can not only effectively inhibit the corrosion of carbon steel, but also protect the environment.In this paper, we have studied the effect of NaNO₂ and NaHCO₃ in simulate concrete pore solution on the corrosion behavior of carbon steel. Electrochemical methods such as polarization curve, EIS test, Mott-Schottky curve test, and also XPS, SEM, EDS were used to measure the corrosion behaviors in four kinds simulate concrete pore solutions:SCP1 ?pH=11, with NaHCO₃??SCP2 ?pH=11, without NaHCO₃??SCP3 ?pH=10, with NaHCO₃? ? SCP4 ?pH=10, without NaHCO₃?.The effect of Cl^- concentrate was also studied on carbon steel with NaNO₂.The inhibiting effect of NaNO₂ on pitting corrosion and uniform corrosion of Q235 carbon steel was analyzed in the case of concrete pore solution containing NaHCO₃ and without NaHCO₃.And themechanism of NaHCO₃ compounded NaNO₂ on the pitting corrosion of Q235 carbon steel was studied. The corrosion resistance effect of inhibitor NaNO₂ compounded D-glucose citrate in SCP1 was studied, in further.The main conclusions are as follows:1?NaNO₂ and NaHCO₃ could prompt carbon steel surface form passivation coating in pore solution containing ?pH 11? 0.1mol/L NaCl, and it reduce the corrosion rate of carbon steel. When the pore solution no existing NaHCO₃ ?SCP2?, NO₂^- has the obvious effect on the inhibiting uniform corrosion of carbon steel; When the pore solution containing NaHCO₃ ?SCP1?, NO₂^- has the little effect on the inhibiting uniform corrosion of carbon steel, but it can significantly reduce the sensitivity of the carbon steel pitting corrosion. Compared with NaHCO₃, NaNO₂ can improve the stability of the surface passivation coating of carbon steel, and it has more stronger ability of inhibition of the stable pitting corrosion. When NaNO₂ along with NaHCO₃ existing, the Fe³⁺/Fe²⁺of passivation coating of the carbon steel is maximum, the defect is least, and the surface coating is strongest, it has obvious effect on inhibition of pitting corrosion.2?In the concrete pore solution ?pH 11? containing different concentrations of Cl^-, NaNO₂ can better reduce the nucleation and the life of metastable pitting corrosion of carbon steel than NaHCO₃, and it can better inhibite the transformation of metastable pitting corrosion to stable pitting corrosion than NaHCO₃. When NaNO₂ along with NaHCO₃ existing, the nucleation and the life of carbon steel metastable pitting corrosion is lowest and shortest, and it the most difficult of the transformation of metastable pitting corrosion to stable pitting corrosion, it means that in SCP1 solution containing NaHCO₃ joining NaNO₂, the effect of curbing carbon steel of metastable pitting corrosion occurring and growing is best.3?In the concrete pore solution ?pH 10? containing different concentrations of Cl^-, NaNO₂ and NaHCO₃ can promote forming the surface passivation coating, and it can reduce the uniform corrosion of carbon steel. When the pore solution no existing NaHCO₃ ?SCP4?, NO₂^-has the obvious effect on the inhibiting uniform corrosion of carbon steel; When the pore solution containing NaHCO₃ ?SCP3?, NO₂^- has a little effect on the inhibiting uniform corrosion of carbon steel, Compared with NaHCO₃, NaNO₂ can improve the stability of the surface passivation coating of carbon steel, and it can inhibit the transformation of metastable pitting corrosion to stable pitting corrosion. in SCP1 solution containing NaHCO₃ joining NaNO₂, the sensitivity of metastable pitting and stable pitting are the lowest.4?Joining the compound inhibitor of NaNO₂ and D-sodi?m gluconate in pore solution containing Cl^-,the corrosion potential and the stable pitting corrosion potential has greatly increased than only adding NaNO₂, and the defect concentration of the passivation film also significantly reduce.The corrosion rate of carbon steel can reach 96.7%, it not only compound inhibitor reduce the uniform corrosion of carbon steel, also can greatly reduce the pitting corrosion sensitivity of carbon steel. According to the results of micro area potential in situ scanning test ?SRET?, adding the compound inhibitor in pore solution, the micro area potential and the active points of carbon steel significantly reduced, this means that it has obvious inhibitory effect on the metastable pitting corrosion.