吐温-40 与植酸复配对碳钢的缓蚀作用

目的提高0.5 mol/L HCl中植酸对热轧碳钢(HRCS)的缓蚀性能。方法用失重法和电化学阻抗法测试植酸、吐温-40以及复配缓蚀剂的缓蚀效率,从热力学和动力学方面分析复配缓蚀剂的作用机制。结果失重法测试表明,植酸和吐温均对热轧碳钢有一定缓蚀作用。当293 K,植酸质量浓度为0.3g/L时,缓蚀效率达到69.1%,在质量浓度为0.8 g/L时缓蚀效率下降为9.6%;吐温-40的缓蚀效率随着质量浓度的增大而增大,0.8 g/L时达到73.4%。在0.5 mol/L盐酸中加入0.05 g/L吐温-40后,复配缓蚀剂的缓蚀效率随着质量浓度的增加而增大,且优于植酸和吐温-40单独使用,表现出协同效应。电化学测试得到了相同的结论,表明复配缓蚀剂在碳钢表面产生自发的Langmuir吸附,使碳钢腐蚀反应的活化能增大,是熵减少的放热过程。结论吐温-40和植酸在盐酸中对热轧碳钢的腐蚀有缓蚀协同作用。

Inhibition Effect of the Composite of Tween-40 and Phytic Acid on Carbon Steel

Objective To improve the corrosion inhibition performance of phytic acid for hot rolled carbon steel (HRCS) in 0. 5 mol/ L HCl soltuion. Methods The corrosion inhibition efficiency of phytic acid, Tween-40, and their compound on carbon steel was measured by weight-loss method and electrochemical impedance spectrometry tests. The inhibition mechanism of the compound inhibitor was analyzed using thermodynamics and kinetics. Results It was revealed by weight-loss measurement that either phytic acid or tween-40 alone had limited inhibitory effect on the corrosion of HRCS in hydrochloric acid. The inhibition efficiency of phytic acid reached the max value of 69. 1% when the concentration was 0. 3 g/ L at 293 K, then decreased with further addition of inhibitor and was reduced to 9. 6% when the concentration of phytic acid was 0. 8 g/ L. On the other hand, the inhibition efficiency increased with the increase of the tween-40's concentration, which reached the value of 73. 4% at 0. 8 g/ L, 293 K. When Tween40 (0. 05 g/ L) was added into the solution, the inhibition efficiency of the compound inhibitor increased even if the concentration of phytic acid exceeded 0. 3 g/ L. The corrosion inhibition efficiency of compound inhibitor was higher than the sum of phytic acid' s and Tween-40's efficiency, which suggested synergistic effect. The same result could be concluded from electrochemical impedance spectrometry measurement. Further analysis revealed that the adsorption of the compound inhibitor on the surface of carbon steel obeyed Langmuir adsorption isotherm equation, which improved the activation energy(Ea) of the corrosion procession, leading to the decrease of entropy. Conclusion Tween-40 and phytic acid showed synergistic corrosion inhibition effect on the HRCS in hydrochloric acid.