(1 School of Chemistry and Engineering, University of Jinan, Jinan 250022)
(2 School of Environmental Science and Engineering, Beijing Forestry University, Beijing 100083)
(3 Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071)
(4 Institute of Design & Research, Shandong Jianzhu University, Jinan 250013)
The corrosion inhibition and mechanisms of pipemidic acid (8-ethyl-5-oxo-5,8-dihydro-2-(1- piperazinyl)pyrido[2,3-d]pyrimidine-6-carboxylic acid), levofloxacin [(±)-9-fluoro-2,3-dihydro-3- methyl-10-(4-methyl-1-piperazinyl)-7-oxo-7H-pyrido[1,2,3-de][1,4]benzoxazine-6-carboxylic acid] and ciprofloxacin [l-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazinyl)-3-quinoline carboxylic acid) for mild steel in 0.5 mol/L H2SO4 was studied using weight loss experiment, potentiodynamic polarization curves, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) at 303 K. The results obtained from weight loss experiment showed the inhibition efficiency was significantly increased with the inhibitor concentration increasing. Electrochemical corrosion experiment revealed the inhibition process was related to the inhibitor molecules covering on the metal surface, which mainly inhibited cathode hydrogen evolution reaction. The inhibitor molecules on the mild steel surface obeyed Langmuir isothermal model and involved physical adsorption and chemical adsorption at 303 K. Scanning electron microscopy observations showed the three inhibitors played a significant protective effect on metal corrosion. All the test results concluded that ciprofloxacin inhibition performance was best under the same conditions.