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1 Polish Journal of Materials and Environmental Engineering

1 2022

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Charakterystyka fizyczna i chemiczna osadów korozyjnych w rurach żelaznych eksploatowanych w obecności przepływu wody

Przywara Lucyna, Jaszczurowska Agnieszka

Polish Journal of Materials and Environmental Engineering

2022

Vol. 4 (24)

30--40

The presented paper contains issues related to corrosion of water supply lines formed in cast iron and steel. This process can manifest in different ways, including pipe degradation, release of iron by-products, water flow restriction, microbial growth and the reduction of drinking water safety for consumers, which present a significant threat to water supply safety. The aim of the paper was to show changes that emerged in pipes formed in grey cast iron and steel as a result of potable water flow depending on the duration of their use. The corrosion scales from old water pipe lines were analyzed for their structure and composition. The description of the test methodology presents the procedure regarding, analysis of the inner and outer coating with the use of scanning equipment, and chemical analysis of the corrosion sludge. In this study, corrosion products were carefully collected from four old, corroded iron pipes made of different materials – gray cast iron and steel. It can be concluded that scale charac-teristics, including micromorphology, porosity and composition, vary significantly due to different pipe materials and times operating. Characteristics of corrosions scales sampled from different pipe segments show obvious differences, both in physical and chemical aspects. Corrosion scales were found highly amorphous. Diverse results can be observed in the case of the test of inner and outer surface of water supply pipes with the use of scanning equipment. The highest quantity of corrosion pits in the structure were present in the line formed in grey cast iron no. 2, while the deepest pits – over 14 mm – were recorded in steel pipe no. 4. Lines with the most reduced cross-section include steel pipe no. 3, which was characterized by presence of sludge sized over 26 mm. When considering the issue of the chemical composition of the formed corrosion sludge, particular attention must be drawn to the elements that may penetrate into water as a result of its flow, thus causing a considerable deterioration of its quality in chemical and physical terms. Among the major constituent elements of the deposits, iron was most prevalent followed, in the order of decreasing prevalence, by silicon, aluminum, sulfur, calcium, manganese, magnesium. Consequently, characterization of corrosion scales is indispensable to water quality protection.