Corrosion in the form of seamless steel pipe for buried pipelines are divided into two kinds of localized corrosion and uniform corrosion, localized corrosion mostly dominated, the danger is also the largest. Pipe in the soil erosion process is mainly electrochemical dissolution process, due to the formation of a corrosion cell causing corrosion of the pipe perforation. Press corrosion cell anode and the cathode region of the size of the pitch, but also form a corrosion cell corrosion steel pipe into micro and macro cell corrosion two categories. The so-called micro-cell corrosion, refers to the role of a few millimeters from the pipeline micro-cell or even just a few microns apart anode and cathode consisting caused by corrosion. Its shape is very uniform characteristics, it is also called uniform corrosion. Since the micro-micro anode and cathode separated by very close, so the micro-cell corrosion rate does not depend on the resistivity of the soil, only slightly depends on the anode and cathode electrodes micro process. Micro cell corrosion of buried steel pipe less harmful.
The so-called macro-cell corrosion, galvanic action macro refers pipeline by the distance of a few centimeters or even meters of anode and cathode region composed caused by corrosion. Macrocell corrosion, also known as localized corrosion. Since the anode region and the cathode region far away from the soil medium resistance accounts for a considerable proportion of the corrosion cell circuit total resistance, so the macro cell corrosion speed in addition to the anode and cathode electrode process related, but also with the soil resistivity related. Great soil resistivity can be reduced by the macro cell corrosion speed. That is caused by the macro cell corrosion in buried pipe or a hole in the surface of the plaque-like corrosion, the danger is considerable.
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