Automatic Welding, 2023, №05



2023 №05 (05)

DOI of Article 10.37434/as2023.05.06

2023 №05 (07)

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Avtomaticheskaya Svarka (Automatic Welding), #5, 2023, pp. 48-53

Investigation of corrosion of enamel cold water supply pipes

S.O. Osadchuk, L.I. Nyrkova, L.V. Goncharenko

E.O. Paton Electric Welding Institute of the NAS of Ukraine. 11 Kazymyr Malevych Str., 03150, Kyiv, Ukraine. E-mail: office@paton.kiev.ua

The pipe of carbon steel with inner silicate-enamel coating was investigated, which was damaged during operation in the system of cold water supply during 5 years. According to the results of the visual inspection, it was revealed that the electric welded pipe and corrosion damages in the form of crevices were formed after damage to the protective coating on the electric weld. It is shown that the transitional specifi c electric resistance on the surface with an electric weld is low (1.5 Ohm·m2) compared to this indicator on the base metal (907 Ohm·m2), which indicates the practical absence of its protective ability. Metallographic examinations showed that the cause of fracturing the pipe specimen is defects of non-fusion of the sheet edges during manufacture. The identifi ed type of corrosion is a crevice that propagated on the inner surface of the pipe at the points of non-fusion of weld edges. Over the 5 years of operation, the rate of crevice corrosion was 0.8 mm/year and was accompanied by the formation of through lesions, and the corrosion durability in the crevice was estimated in accordance with GOST 9.502, as “reduced” (from 0.5 to 1.0 mm/year). It was concluded that the corrosion durability and fatigue life of the studied enamel pipe is determined by the quality of producing electric welded joint. 14 Ref., 2 Tabl., 4 Fig.
Keywords: enamel pipes, carbon steel, silicate-enamel coatings, electric weld, corrosion durability, corrosion rate


Received: 29.03.2023

References

1. Tyrala, D., Pawlowski, B. (2021) Failure аnalysis of premature corrosion of HF seam-welded steel pipe in central heating system. Fail. Anal. and Preven., 21, 772-778. https://doi.org/10.1007/s11668-021-01134-6
2. Živković, D., Mišina, N., Ljumović, P. (2017) Corrosion damage of seam welded galvanized hot water pipelines. Tehnički vjesnik, 24(4), 1007-1012. https://doi.org/10.17559/TV-20170112142442
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14. GOST 5639-82 Steels and alloys. Methods for detection and determination of grain size [in Russian].

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