摘要
Abstract
Nuclear power plant safety is a crucial prerequisite for the development of nuclear energy,and the fire is a significant hazard during the construction and operation of nuclear power plants,requiring focused prevention.The fire water system plays a vital role in extinguishing fires.Ductile iron pipes are commonly used for fire water systems,and assessing their corrosion behavior and condition during service is the key to ensuring the reliability of the fire water system.However,the current research on the corrosion of ductile iron pipes mainly focuses on environments such as municipal water and tap water,with relatively few researches in fire water environments.There is also a lack of analytical evaluations of their corrosion and wear behavior.
The work aims to clarify the electrochemical and wear behaviors of ductile iron in the fire water environment of nuclear power plants to provide support for its safe service and life assessment.The electrochemical properties of the ductile iron pipes in a simulated fire water environment were carefully studied through open circuit potential(OCP),electrochemical impedance spectroscopy(EIS)and potentiodynamic polarization measurements.The corrosion rate and corrosion behavior of the ductile iron were analyzed through immersion experiments with a total period of 30 days.Meanwhile,the friction coefficient of the corroded samples after immersion was studied with a tribometer.After test,the surface morphology,corrosion products,three-dimensional contour characteristics,and wear depth of the corroded samples were analyzed with SEM,EDS,and white light interferometry techniques.
The results indicated that with the extension of time,the OCP value and electrochemical impedance value of ductile iron in the simulated fire water environment gradually decreased,while the corrosion current density increased nearly by a factor of two,from 5.56×10-6 A/cm2 to 1.05× 10-5 A/cm2.This suggested an increase in the electrochemical activity of ductile iron and a significant weakening of its corrosion resistance.As the immersion time extended to 30 days,the corrosion rate of ductile iron in the simulated fire water environment showed a gradual decline,decreasing from about 30.2 mm/a to 5.56 mm/a.The corrosion products on the surface of ductile iron gradually accumulated,with the products mainly consisting of Fe oxides,Si oxides,etc.After the corrosion products were removed,the surface of ductile iron exhibited non-uniform corrosion characteristics with few corrosion pits,and the depth of the corrosion pits increased continuously with the extension of immersion time.After 30 days of immersion,the maximum depth of the surface corrosion pits reached up to 39.26 μm.The friction coefficient of ductile iron after immersion gradually increased as the immersion time extended,and the depth of the grooves on the surface after friction increased from approximately 2.25 mm to about 21.32 mm.To sum up,the corrosion and wear resistance of ductile iron in the simulated fire water environment of nuclear power plants gradually decreases with the extension of immersion time and the corrosion rate exhibits a power-law decrease,while the friction depth shows a power-law increasing trend.关键词
球墨铸铁/电化学/消防水/腐蚀形貌/核电站/摩擦磨损/表面轮廓Key words
ductile iron/electrochemistry/fire water/corrosion morphology/nuclear power plant/friction and wear/surface profile分类
矿业与冶金
