Corrosive and Mechanical Degradation of Pipelines in Acid Soils

Abstract

The effect of in-service degradation on the deformation behavior of the material of gas mains in soil acid electrolytes has been studied, and it has been shown that depending on the concentration of the corrosive components of the environment, the strain increment can be up to 20-30%. It has been found that in soil acid electrolytes, degraded pipeline steel shows a tendency to sudden strain jumps, which can cause spontaneous depressurization of the pipeline.

Corrosion-mechanical behavior of gas main steel in saline soils

“…We can conclude that the chloride-sulfate electrolytes are much more dangerous from the point of view of corrosion. This is due to many factors, the most important of which is synergistic action of corrosive ions Cland SO 4 2found in previous studies [6] and cause the significant localization of corrosion processes. The same reason leads to accelerated growth of existing defects caused by the formation of galvanic couples "the old surface -the newly formed surface" or others with a similar mechanism.…”

“…Such corrosion-mechanical behavior of pipe steel can be explained by synergistic effect of corrosion and mechanical factors as the level of stress, as shown by the results of the tests in the air is insufficient for such a long intense deformation rate. A major factor, that cause reduction of pipeline steel bearing capacity is the corrosion influence of soil electrolyte (due to the formation of new and development of existing defects) [4,[6][7]21].This evidenced by the kinetics of deformation on the air with virtually the last horizontal section.…”

“…Exposure time was 30000 minutes. During the experiment the kinetics of creep deformation (Δε c ) and corrosion creep deformation was studied (Δε cc ) [6].…”

“…That is why, study of changes in physical and mechanical properties of the pipeline material in operation process will better determine the resource of gas pipelines constructions. Moreover, there is a rising importance of existing pipelines operability maintaining in today's conditions [4][5][6][7].…”

“…Also there are many additional and variable in time parameters that are taken not only from handbooks but also determined experimentally. List of only most significant factors determining the corrosion activity of soils, which are the structure and analysis, humidity, composition of the soil electrolyte, the total acidity or alkalinity of the soil, the concentration of hydrogen ions, air penetration redox potential, electrical resistivity of soils, indicate the complexity of the mathematical modeling of deformable system "pipe-soil massive" and thus prediction of the durability of the underground pipeline [6,11].…”