The work describes the experimental definition of the main factors that contribute to the emergence of grooving corrosion: availability of abrasive particles in flow which are transported in specific terms when they are capable of scratching the bottom generating line of a pipeline by creating stress concentrators; availability of considerable residual stresses in pipe metal; oxygen availability in reaction zone.

A series of experiments on measuring of difference between the main mechanical stresses (DPMS) was carried out using a mechanical stress scanner based on the magnetoanisotropic method. The magnitude of the DPMS is fixed when a magnetic field is induced on a carbon steel plate under uniaxial tension. A direct proportional relationship is shown between the magnitude of the DPMS signal recorded by the scanner and the magnitude of tensile stresses in the plate in the region of elastic deformation of steel. Measurement of the DPMS signal in the central part of similar plates previously subjected to elastic-plastic bending showed that positive values of the signal are fixed in the surface layers of the metal on the inside of the plate, which corresponds to tensile residual stresses, while the negative ones concentrate at the external surface, which corresponds to compressive stresses. A transverse incision on a curved plate from the inside leads to a decrease in the value of the signal of the DPMS, which indicates a decrease in the level of residual stresses in the metal. The values of the DPMS signal in the central part of the curved plate, recalculated using the established calibration dependence on the value of the residual stresses, were compared with the values of the stresses established by calculation, based on the Henki’s theorem on the unloading of an elastic-plastic body. A satisfactory convergence was obtained between the experimental and calculated data.

The results of a calculation analysis of the stress-strain state of a fragment of pipes of four sizes under working pressure are presented in the presence of an oval-shaped longitudinal incision on their inner surface, the appearance of traces of grooving corrosion. It is shown that under the influence of emerging stresses, the maximum value of which is reached in the notch bottom metal, the section of the pipe with an incision is «pressed» into the pipeline and corrodes at an increased speed exceeding the corrosion rate of an intact pipe up to 2.2 times.

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