Page 6 - Dys_Usov 2021

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for cathode protection, its influence on the state of anode earthing switches, as well
as the development of methods for improving the efficiency of their work and

extension of the resource.
The steel pipeline after 51 years of operation was investigated, it has been

established that at the time of supply steel 20, has a ferrite - a perlite structure with
a perlite grain ratio to ferrite 35/65 on a scale of 7 GOST 8233, during operation,

the decomposition of perlite and the perlite / ferrite ratio has occurred 20 / 80,

indicating significant degradation processes in steel microstructure. It is

determined that the amount of hydrogen on the metal metal was within the normal

range, but in the sample from the plot number 2, it is larger compared to other

areas, it is most likely due to the damaged insulating coating.

It is proved that the density of corrosion current is sufficiently sensitive to

changes in the state of the metal as a result of exploitation and depends on the

distance of the site to the cathode station. The smallest density of corrosion current
2
-4
I = 0.56 ∙ 10 A/cm is characterized by a metal portion 1 (0.5 km from the
cor
-4
2
cathode station), and the largest (1,25 ∙ 10 A/cm ) – steel sections 2, which
operated at a distance of 8 km from the cathode station and for which the violation

of the integrity of the protective coating was recorded;

It has been established that the characteristics of the strength of samples of

supply pipeline and at a distance of 0.5 km, 8 km, 15 km from the cathode station,

are not significantly changed in the range of permissible values.
It is observed for plasticity indicators (δ, ψ), only for a sample at a distance

of 0.5 km relative elongation decreases by ~ 1.3 times.

It has been determined that the impact strength (КCU) of the 20 steel

operated at a distance of 0.5 km, 8 km, 15 km from the cathode station is decreased

in ~ 1.1; 1.2 and 1.5 times, respectively.

It has been established that the chemical composition of the metal

corresponds to the current requirements of pipe steels, steel steel 20 and steel steel

12Х18Н10Т respectively.

The state of metal anode grounding from steel 20 after 20.5 years of