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 dia...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 ℃.展开更多
The influence of dissolved oxygen on calcareous deposits formed under galvanostatic polarization mode was studied.When the dissolved oxygen concentration was less than 7 mg L^(-1),the cathodic protection potential sho...The influence of dissolved oxygen on calcareous deposits formed under galvanostatic polarization mode was studied.When the dissolved oxygen concentration was less than 7 mg L^(-1),the cathodic protection potential showed a plateau at the initial polarization,and then quickly shifted negatively.While the dissolved oxygen was more than 9 mg L^(-1),the potential shifted negatively in a linear form.After 168 h of polarization,the final protection potential shifted negatively with the decreasing dissolved oxygen concentration.The deposition progress was monitored by electrochemical impedance spectroscopy,and only one single loop was found in Nyquist diagram,indicating deposits of ineffective protectiveness precipitation under the experimental conditions.The protection factor of deposits increased with the decreasing dissolved oxygen concentration which was detected by linear polarization resistance technique.The cathodic electrochemical reaction could change very shortly from oxygen reduction to hydrogen evolution after cathodic protection under very low dissolved oxygen concentration,such as 1 mg L^(-1),resulting in the hydrogen bubbling from the metallic surface and the decrease of deposits protection factor.Observation by scanning electron microscopy and X-ray diffraction analysis demonstrated that the deposits were mainly of calcite under the experimental conditions,and that dissolved oxygen had no effect on the crystalline types of calcium carbonate.展开更多
盐类物质、水和泥沙等腐蚀介质会加快海洋环境对金属构架物的腐蚀,严重影响港口、石油平台等海洋工程中金属结构的性能。为了减少复杂海洋环境对金属构架的腐蚀破坏,工程上通常采用外加电流阴极保护法(ICCP,Impressed current cathodic ...盐类物质、水和泥沙等腐蚀介质会加快海洋环境对金属构架物的腐蚀,严重影响港口、石油平台等海洋工程中金属结构的性能。为了减少复杂海洋环境对金属构架的腐蚀破坏,工程上通常采用外加电流阴极保护法(ICCP,Impressed current cathodic protection)的腐蚀防护方案对金属构架进行保护。针对ICCP海洋腐蚀防护工程的应用,从电解池组成的角度进行梳理分析,对电解质、外加电源和阴阳电极层面涉及的关键问题进行了总结。展开更多
The electrochemical impedance spectra for bare steel and sample covered with calcareous deposit in artificalseawater were determined; the dependence of the impedance on the potential was investigated, thesignificance ...The electrochemical impedance spectra for bare steel and sample covered with calcareous deposit in artificalseawater were determined; the dependence of the impedance on the potential was investigated, thesignificance of the impedance parameter R_f reflecting the effective protectiveness of the deposit is emphasized.Optimization of the cathodic polarization condition is discussed.展开更多
基金financially supported by the National Science and Technology Major Project of China(No. 2011ZX05027-004-06)
文摘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 ℃.
基金the financial support of this project by the National Basic Research Program of China(973 Project,No.2014CB643300)National Environmental Corrosion Platform(NECP)
文摘The influence of dissolved oxygen on calcareous deposits formed under galvanostatic polarization mode was studied.When the dissolved oxygen concentration was less than 7 mg L^(-1),the cathodic protection potential showed a plateau at the initial polarization,and then quickly shifted negatively.While the dissolved oxygen was more than 9 mg L^(-1),the potential shifted negatively in a linear form.After 168 h of polarization,the final protection potential shifted negatively with the decreasing dissolved oxygen concentration.The deposition progress was monitored by electrochemical impedance spectroscopy,and only one single loop was found in Nyquist diagram,indicating deposits of ineffective protectiveness precipitation under the experimental conditions.The protection factor of deposits increased with the decreasing dissolved oxygen concentration which was detected by linear polarization resistance technique.The cathodic electrochemical reaction could change very shortly from oxygen reduction to hydrogen evolution after cathodic protection under very low dissolved oxygen concentration,such as 1 mg L^(-1),resulting in the hydrogen bubbling from the metallic surface and the decrease of deposits protection factor.Observation by scanning electron microscopy and X-ray diffraction analysis demonstrated that the deposits were mainly of calcite under the experimental conditions,and that dissolved oxygen had no effect on the crystalline types of calcium carbonate.
文摘盐类物质、水和泥沙等腐蚀介质会加快海洋环境对金属构架物的腐蚀,严重影响港口、石油平台等海洋工程中金属结构的性能。为了减少复杂海洋环境对金属构架的腐蚀破坏,工程上通常采用外加电流阴极保护法(ICCP,Impressed current cathodic protection)的腐蚀防护方案对金属构架进行保护。针对ICCP海洋腐蚀防护工程的应用,从电解池组成的角度进行梳理分析,对电解质、外加电源和阴阳电极层面涉及的关键问题进行了总结。
基金This work was a key project of the Chinese Academy of Sciences(KY85-11)
文摘The electrochemical impedance spectra for bare steel and sample covered with calcareous deposit in artificalseawater were determined; the dependence of the impedance on the potential was investigated, thesignificance of the impedance parameter R_f reflecting the effective protectiveness of the deposit is emphasized.Optimization of the cathodic polarization condition is discussed.
