阳离子表面活性剂对冷轧钢在H_(2)SO_(4)中的缓蚀作用

Inhibition effect of cationic surfactant on cold rolled steel in H_(2)SO_(4)

采用失重法、动电位极化曲线、电化学阻抗谱(EIS)、溶液表面张力测试、接触角测试以及扫描电子显微镜(SEM)探究了阳离子表面活性剂十八烷基三甲基氯化铵(OTAC)在0.5 mol/L H_(2)SO_(4)溶液中对冷轧钢的缓蚀作用.研究结果表明:OTAC具有良好的缓蚀效果,缓蚀率随OTAC浓度的增加而增大,但随温度的升高而减小,20℃时100 mg/L OTAC的缓蚀率可达87.1%.OTAC在钢表面的吸附符合Langmuir等温式,吸附方式为物理吸附和化学吸附.冷轧钢在0.5 mol·L^(-1)H_(2)SO_(4)溶液中的腐蚀速率与温度的变化关系符合Arrhenius方程和过渡态理论方程,随着OTAC浓度的增加,表观活化能(E_(a))、表观活化焓(△H_(a))、表观活化熵(△S_(a))以及指前因子(A)先增大后趋于平缓.动电位极化曲线结果表明OTAC是混合抑制型缓蚀剂.Nyquist图谱主要由高频区的容抗弧组成,随OTAC浓度的增加,容抗弧半径有规律地增大,电荷转移电阻增大.OTAC溶液表面张力随浓度的增加先急剧减小后趋于平缓,0.5 mol·L^(-1)H_(2)SO_(4)溶液中OTAC的临界胶束浓度(CMC)约为20 mg·L^(-1).OTAC的加入使得钢片表面的疏水性增强.冷轧钢表面的SEM微观形貌进一步证实了OTAC能有效减缓H_(2)SO_(4)介质对钢表面的腐蚀.

The inhibition effect of the cationic surfactant of octadecyl trimethylated ammonium chloride(OTAC)on cold rolled steel(CRS)in 0.5 mol·L^(-1)H_(2)SO_(4)solution was studied by weightlessness,potentiodynamic polarization curves,electrochemical imped-ance spectrum(EIS),solution surface tension measurements,contact angle tests and scanning electron microscope(SEM).The re-sults show that OTAC is of good anti-corrosion suppression effect,and the inhibition efficiency increases with the increase of OTAC concentration,while decreases with the experimental temperature.The inhibition efficiency of 100 mg/L OTAC at 20℃isashighas 87.1%.The adsorption of OTAC on the steel surface is in accord with Langmuir isotherm,and the adsorption mode is composed of both physical adsorption and chemical adsorption.The relationship between corrosion rate and temperature of cold rolled steel in O.5 mol·L^(-1)H_(2)SO_(4)solution is in line with the Arrhenius equation and the transition state theoretical equation.Along with the increase of OTAC concentration,the apparent activation energy(E_(a)),the apparent activation enthalpy(△H_(a)),the apparent activation entropy(△S_(a))and thepre-exponential factor(A)will firstly increaseand then flatten out.Thepotentialdynamic polarization curvesshow that OTAC is a mixed-type inhibitor.Nyquist graph is mainly composed of the capactive loop in the high-frequency region.With the increase of OTAC concentration,the capactive arc resistance radius increases regularly,and the transfer charge resistance is also in-creased.The surface tension of OTAC solution decreases sharply with the increase of concentration,and then attains to be steady state.The critical micelle concentration(CMC)of OTAC in O.5 mol·L^(-1)H_(2)SO_(4)solution is 20 mg·L^(-1).The contact angle test shows that the addition of OTAC enhances the hydrophobicity of the steel sheet surface.The micro-morphology of the SEM on the cold-rolled steel surface further confirms that OTAC can effectively reduce the corrosion of the steel surface by sulfuric acid medium.