The adsorption-type inhibitors play an important role in preventing corrosion of metals in acidic solutions, so the study of the relations between the adsorption and corrosion inhibition is of great importance. Dodecylamine is considered as adsorption-type inhibitor for carbon steel in acidic solutions [1]. Polarization curve measurement is commonly employed in inhibitor research. For example, the modes of inhibition effect of interface inhibitors can be classified by polarization curve [2], corrosion current densities or inhibition efficiencies are often estimated by extrapolation of polarization curves to corrosion potentials. In some cases, equations of adsorption isotherms of interface inhibitors are obtained from plots of the inhibition efficiencies vs concentrations of the inhibitors studied [3–6]. Atomic force microscopy (AFM) is receiving considerable attention in the field of surface science and engineering, it has also been successfully applied to the investigation of corrosion processes and proofed to be an excellent tool [7, 8], however since the roughness of the surface is much higher compared with adsorption film, especially when the film is monolayer, it is very difficult to evaluate the adsorption behavior of inhibitors through imaging surface topography, but the conductivity of the surface will be changed after the adsorption of inhibitor, and the force curves will also exhibit different characters after the adsorption of inhibitor. The application of AFM current image and force curves will be new ways to investigate the adsorption behavior of inhibitor. The aim of this study is to present new methods to evaluate the inhibitor adsorption behavior. Firstly, the polarization curves were applied to study the adsorption behavior of dodecylamine on carbon steel, then the current image and force curves of carbon steel surface after immersion in test solution containing inhibitor were measured. All the tests were performed on carbon steel of the following composition (wt.%): C, 0.24; Mn, 1.19; P, 0.013; S, 0.004; Cr, 0.036; Mo, 0.021; Ni, 0.028; Fe, Remainder. The base solution was HCl solution, and the inhibitor is dodecylamine. All the solutions were prepared from analytical grade reagents and distilled water. The electrochemical measurements were conducted through a three-electrode cell connected to a Zahner IM6e electrochemical workstation. A platinum electrode and a saturated calomel electrode (SCE) were used as reference electrode and counter electrode respectively. Polarization curves were obtained by sweeping the potential from a value of )200 to 200 mV vs. Ecorr with a potential scan rate of 0.5 mV s. The working electrode for electrochemical tests was embedded in PTFE ring leaving an area of 1 cm exposed to solution. Before tests, the samples were wet ground through 1200 grit SiC paper, rinsed with distilled water and ethanol, dried at room temperature. The topography of the sample surface was measured with a commercial AFM system (SPI3800, Seiko Instruments Inc.) operated in contact mode, and the current image was simultaneously measured by applying a bias voltage of 0.5 V between the sample and the Au-coated conductive tip. Specimens for AFM measurement were wet ground through 1200 grit SiC paper, and then polished to 0.5 lm with diamond paste using a polishing cloth. After being rinsed with distilled water and treated with supersonic cleaning in ethyl alcohol, the samples were stored in air. Z. Y. Chen AE X. P. Guo (&) AE Q. Zhang AE J. E. Qu Department of Chemistry, Huazhong University of Science and Technology, Wuhan 430074, P R China e-mail: guoxp@mail.hust.edu.cn J Mater Sci (2006) 41:5033–5035 DOI 10.1007/s10853-006-0104-x
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May 21, 2015
Xingxing Gao + 3
Open Access
