The contribution of cinnamon extract on leaching of aluminum (Al) cook wares was investigated using two aluminum alloys (Indian and Egyptian) and pure Al. The cinnamon (Cin) was extracted by heating the Cin sticks at ...The contribution of cinnamon extract on leaching of aluminum (Al) cook wares was investigated using two aluminum alloys (Indian and Egyptian) and pure Al. The cinnamon (Cin) was extracted by heating the Cin sticks at 90°C in distilled water for an hour to make the 10% stock solution. This study was done in aqueous solutions in presence and absence of 1% NaCl using weight loss at 90°C. Moreover surface study (SEM and EDX) and electrochemical methods (Open Circuit Potential and Tafel plot) were applied. The addition of Cin solutions to 1% NaCl decreased the corrosion rates in weight loss and electrochemical method compared to 1% NaCl solutions which showed an inhibitive property of Cin solution. The inhibition was found to obey the modified Langmuir isotherm with a negative Langmuir ΔGads indicating the spontaneous nature of adsorption even at 90°C. The EDX surface analysis of the Al surface immersed in Cin + NaCl revealed the composition of the pits formed. From Tafel method, it was found that the corrosion current density of pure Al was more than that of the Egyptian alloy. The apparent activation energy values for Cin, Cin + NaCl and NaCl solution were evaluated and discussed.展开更多
Abstract Fouling deposits on aluminum heat exchanger reduce the heat transfer efficiency and cause corrosion to the apparatus. This study focuses on the corrosive behavior of aluminum cou- pons covered with a layer of...Abstract Fouling deposits on aluminum heat exchanger reduce the heat transfer efficiency and cause corrosion to the apparatus. This study focuses on the corrosive behavior of aluminum cou- pons covered with a layer of artificial fouling in a humid atmosphere by their weight loss, Tafel plots, electrochemical impedance spectroscopy （EIS）, and scanning electron microscope （SEM） observations. The results reveal that chloride is one of the major elements found in the fouling which damages the passive film and initiates corrosion. The galvanic corrosion between the metal and the adjacent carbon particles accelerates the corrosive process. Furthermore, the black carbon favors the moisture uptake, and gives the dissolved oxygen greater chance to migrate through the fouling layer and form a continuous diffusive path. The corrosion rate decreasing over time is conformed to electrochemistry measurements and can be verified by Faraday＇s law. The EIS results indicate that the mechanism of corrosion can be interpreted by the pitting corrosion evolution mechanism, and that pitting was observed on the coupons by SEM after corrosive exposure.展开更多
The interaction of imidazole with Co electrodes in an electrochemical system was studied by surface-enhanced Raman scattering (SERS) and electrochemical methods. The SER spectra of Co in an imidazole solution as a fun...The interaction of imidazole with Co electrodes in an electrochemical system was studied by surface-enhanced Raman scattering (SERS) and electrochemical methods. The SER spectra of Co in an imidazole solution as a function of the applied potential were analyzed and the assignment of the Raman bands was made. It was found that there were three kinds of sur-face species on the Co surface in different potential regions and they were interchangeable de-pending on the potential. In a relatively negative potential region (?1.2 to ?0.9 V), imidazole was adsorbed on the surface and its orientation might change from a vertical configuration via the N-end of the pyridine ring to a tilted configuration via the C2=N3 double bond. In a more positive potential region (?0.8 to ?0.7 V), the SERS signal from the adsorbed imidazole weakened and finally disappeared, meanwhile the signal from the Co and imidazole complex strengthened gradually. At the open circuit potential (?0.6 V), we detected very strong bands from the Co ox-ides. By comparing the Tafel curves of the Co electrode in the solution without and with imidazole, we found that imidazole has a marked effect on the corrosion inhibition of the Co electrode. This result demonstrates that we may be able to reveal the complicated interaction of surface species with metal surface at the molecular level by combining the SERS and electrochemical methods.展开更多
文摘The contribution of cinnamon extract on leaching of aluminum (Al) cook wares was investigated using two aluminum alloys (Indian and Egyptian) and pure Al. The cinnamon (Cin) was extracted by heating the Cin sticks at 90°C in distilled water for an hour to make the 10% stock solution. This study was done in aqueous solutions in presence and absence of 1% NaCl using weight loss at 90°C. Moreover surface study (SEM and EDX) and electrochemical methods (Open Circuit Potential and Tafel plot) were applied. The addition of Cin solutions to 1% NaCl decreased the corrosion rates in weight loss and electrochemical method compared to 1% NaCl solutions which showed an inhibitive property of Cin solution. The inhibition was found to obey the modified Langmuir isotherm with a negative Langmuir ΔGads indicating the spontaneous nature of adsorption even at 90°C. The EDX surface analysis of the Al surface immersed in Cin + NaCl revealed the composition of the pits formed. From Tafel method, it was found that the corrosion current density of pure Al was more than that of the Egyptian alloy. The apparent activation energy values for Cin, Cin + NaCl and NaCl solution were evaluated and discussed.
基金supported by the National Natural Science Foundation of China(No.21303261)the Major Science&Technology Research Project of Civil Aviation of China(No.MHRD20140110)
文摘Abstract Fouling deposits on aluminum heat exchanger reduce the heat transfer efficiency and cause corrosion to the apparatus. This study focuses on the corrosive behavior of aluminum cou- pons covered with a layer of artificial fouling in a humid atmosphere by their weight loss, Tafel plots, electrochemical impedance spectroscopy （EIS）, and scanning electron microscope （SEM） observations. The results reveal that chloride is one of the major elements found in the fouling which damages the passive film and initiates corrosion. The galvanic corrosion between the metal and the adjacent carbon particles accelerates the corrosive process. Furthermore, the black carbon favors the moisture uptake, and gives the dissolved oxygen greater chance to migrate through the fouling layer and form a continuous diffusive path. The corrosion rate decreasing over time is conformed to electrochemistry measurements and can be verified by Faraday＇s law. The EIS results indicate that the mechanism of corrosion can be interpreted by the pitting corrosion evolution mechanism, and that pitting was observed on the coupons by SEM after corrosive exposure.
基金supported by the National Natural Science Foundation of China(Grant Nos.29873033,20212&90206039)the State Key Laboratory for Physical Chemistry of Solid Surfaces of Xiamen University.
文摘The interaction of imidazole with Co electrodes in an electrochemical system was studied by surface-enhanced Raman scattering (SERS) and electrochemical methods. The SER spectra of Co in an imidazole solution as a function of the applied potential were analyzed and the assignment of the Raman bands was made. It was found that there were three kinds of sur-face species on the Co surface in different potential regions and they were interchangeable de-pending on the potential. In a relatively negative potential region (?1.2 to ?0.9 V), imidazole was adsorbed on the surface and its orientation might change from a vertical configuration via the N-end of the pyridine ring to a tilted configuration via the C2=N3 double bond. In a more positive potential region (?0.8 to ?0.7 V), the SERS signal from the adsorbed imidazole weakened and finally disappeared, meanwhile the signal from the Co and imidazole complex strengthened gradually. At the open circuit potential (?0.6 V), we detected very strong bands from the Co ox-ides. By comparing the Tafel curves of the Co electrode in the solution without and with imidazole, we found that imidazole has a marked effect on the corrosion inhibition of the Co electrode. This result demonstrates that we may be able to reveal the complicated interaction of surface species with metal surface at the molecular level by combining the SERS and electrochemical methods.
