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Influence of Temperature on the Protectiveness and Morphological Characteristics of calcareous deposits Polarized by Galvanostatic Mode

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Acta Metallurgica Sinica(English Letters) 2014年第1期27卷 131-139页

作者： Chengjie Li Min Du Jing Qiu Jing Zhang Congjie Gao The Key Laboratory of Marine Chemistry Theory and Technology Ministry of EducationCollege of Chemistry and Chemical EngineeringOcean University of China

The influence of temperature on calcareous deposits formed under galvanostatic polarization mode was studied. The deposition was monitored by electrochemical impedance spectrum, and a supplementary loop in Nyquist diagram at high frequency was found to be an indicator of deposits precipitation with sufficient protection at above 20 ~C. An exponential increase of protectiveness with temperature was observed, which was quantified by linear polarization resistance technique. Observation by scanning electron microscope and X-ray diffraction analyses demonstrated that the critical temperature of calcium carbonate crystal form transition ranged from 15 to 20 ℃. Calcite formed below 15 ℃, while aragonite precipitated at above 20 ℃.

关键词： calcareous deposits Temperature Galvanostatic Cathodic protection

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Verification of Levich Law-Determination of Hydrogen Currents during calcareous Deposition

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Journal of Environmental Science and Engineering 2011年第10期5卷 1269-1275页

作者： N. Ghemmit Doulache H. Khireddine D. Si Salah Laboratory of Fibrous Polymers Treatment and Forming Faculty of Engineering Science University M＇hamed Bougara Boumerdes 35000 Algeria Laboratory of Environmental Engineering Department of Engineering Process Faculty of Technology University of Bejaia Targa Ouzemour 06000 Algeria Gas Department lAP Boumerdes Algerian Institute of Oil Boumerdes 35000 Algeria

The complexity of calcareous deposits processes in a marine environment results in simultaneous effects of the following parameters： temperature, polarization potential, interfacial pH, chemical composition, etc.. The comprehension of these processes implies studies in artificial seawater and a follow-up of the parameters by voltarnperometry and chronoamperometry. calcareous deposits electrochemically are very often used to follow up the evolution of scale deposition in desalination circuits. Again, the scale formation is brought about by electrochemical reduction of dissolved oxygen. The hydroxyl ions formed on the metallic surface engender a rise of interfacial pH which causes calcareous deposition （CaCOs and Mg（OH）2）. This reaction goes with reaction of hydrogen evolution which could disrupt the formed deposit, A study is carried out in a solution of seawater ASTM without calcium and without magnesium （so that the deposit will not be formed） on a titanium rotating disk electrode monitored between 300 and 1000 rpm. Study shows that Levich criterion is checked for the four values of selected potential on the diffusion plateau and a very cathodic polarization potential and a high temperature favors hydrogen current rate.

关键词： calcareous deposits titanium Levich criterion hydrogen current potential temperature.

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