Inhibition Effects On Carbon Steel With Some Inhibitors Based On Drugs

As an important method to prevent metals from corroding, the use of inhibitors has attracted much attention. Because of their negative effects to the environment, traditional inhibitors have received more and more dispute recent years, so the development of natural, non-toxic corrosion inhibitor has become more important and urgent. Drugs, which can be taken or injiected directly by human body and whose toxicities can be neglected, has become an ideal replacement of inhibitors.In this thesis, weight loss experiment, open circuit potential test, polarization test, EIS and XPS test were applied to to study the impact of some inhibitors based on drugs to the corrosion of carbon steel and their working mechanism. The inhibitors studied are antimony potassium and L-cysteine, the main conclusions are as follows: (1)In 0.1 mol·L'and 0.01 mol·L-1 NaCl solutions, as the concentration of antimony potassium increased, inhibitive efficiency became larger. At pH 5.5, the maximal IEs of 53.3% and 63.2% were observed in two different concentrations of NaCl solution when the inhibitor's concentration was 400 ppm based on weight loss measurement. In the study of IE change as pH varied, the maximal IEs occured at pH 3.5 and 5.5. When immersing time was 12 hours, best inhibition was observed. (2)After respectively adding 0.2 mol·L-1 and 0.15 mol·L1 of NaHCO3 into 0.1 mol·L-1 and 0.01 mol·L-1 NaCl solutios, there were 3 platforms in the polarization curve. Take NaCl+NaHCO3 solution as blank solution, maximal IEs of 89.9% and 95.5% were observed when antimony potassium's concentrations were 400 ppm and 300 ppm. The best Inhibition occurred when immersing time was 12 hours. XPS result showed that the whole molequle of antimony potassium could adsorb to carbon steel and formed a protective film. (3)In 0.01 mol·L'NaCl solution, maximal IE of 80.8% was observed at 400 ppm L-cysteine. Sodium silicate could obviously inhibit pitting corrosion, but had little effect on uniform corrosion. The addition of L-cysteine into 0.01 mol·L-1 NaCl+NiSiO3 solution could significantly decrease the corrosion current density but lower Eb. Taking inhibitive efficiency of uniform corrosion and pitting corrosion, take 200 ppm L-cysteine+2000 ppm NiSiO3 as the best formula.