埋地铸铁海水管失效分析

AN ANALYSIS OF FAILURE IN CAST IRON SEAWATER BURIED PIPE

通过宏观形貌观察、金相分析、能谱分析、微观裂纹及其断口分析,得到输送海水的铸铁管失效的原因为Cl-离子及氧存在下的电化学腐蚀,并对腐蚀机理进行了阐述.

This paper mainly analyses the cause and principle of the failure in cast iron seawater pipe.The pipe is 630 mm of inside diameter and 12 mm of wall thickness.In the inner wall coating was polymer sand plasma.There was a big corroded hole in the pipe.With the help of morphological character and metallographic examination,it was found that on the matrix material there were small holes with different depth and size and only few pearlite matrix was left.With the help of microanalysis,it was found that in the inner wall there were Cl\+- and oxygen.With the help of scanning electron microscope,it was found that in the crack area there was oxide in the shape of line.In the same time it was found the value of rigidity was lower in inner face than in outer face.Through the analysis we can confirm the cause of the failure is the action of electrochemical corrosion and chemical corrosion when the Cl\+- and oxygen were existed.The equation of the electrochemical corrosion is also discussed.