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Effect of Applied Cathodic Protection Potential on Cathodic Delamination of Damaged Epoxy Coating |
Guirong WANG1,2,Yawei SHAO1(),Yanqiu WANG1,Guozhe MENG1,Bin LIU1 |
1. College of Materials Science and Chemical Engineering, Harbin Engineering University, Harbin 150001, China 2. Aviation Industry Chengdu Aircraft Industry (Group) Co., LTD., Chengdu 610092, China |
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Abstract The combined effectiveness of the cathodic protection and epoxy coating for a steel, which is newly developed for offshore platform, as well as the cathodic delamination behavior of the epoxy coating with damages in artificial seawater at room temperature were examined by means of electrochemical impedance spectroscopy (EIS), scanning electron microscope (SEM), energy dispersive spectrum (EDS) and X-ray diffractometer (XRD). Results indicated that as the potential goes down within the selected range of protection potentials of -750~-1050 mV (vs SEC), the delamination area of the coatings increases. The ordinary protection potential -750 mV (vs SEC) for epoxy coatings is no longer applicable for the damaged coatings, while the cathode potential -1050 mV leads to serious hydrogen evolution in the damaged area, resulting in the integrity destruction of the deposited film there, leading to the seriously interfacial alkalization and therewith, the cathodic delamination area increases. However, the protection potential of -850 or -950 mV can inhibit the corrosion of metal on the damaged site of coating. The deposited film formed under -950 mV on the damaged site is composed of Mg(OH)2 and CaCO3 which is of integrity and dense, leading to the best protective effect on the substrate.
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Received: 03 June 2018
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Fund: National Key Research Program of Ministry of Science and Technology(2016YFB0300604) |
Corresponding Authors:
Yawei SHAO
E-mail: shaoyawei@hrbeu.edu.cn
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