The rapid chemically induced corrosion of concrete sewers at high H2S concentration. (1st October 2019)

• Record Type: Journal Article
• Authors: Li, Xuan; O'Moore, Liza; Song, Yarong; Bond, Philp L.; Yuan, Zhiguo; Wilkie, Simeon; Hanzic, Lucija; Jiang, Guangming
• Is Part Of: Water research. Volume 162(2019)
• Page Start: 95
• Page End: 104
• Publication Date: 2019-10-01
• Subjects: Sewer -- Corrosion -- Concrete -- Hydrogen sulfide -- Chemically induced corrosion; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2019.06.062
• Languages: English
• ISSNs: 0043-1354

Abstract

Abstract: Concrete corrosion in sewers is primarily caused by H2 S in sewer atmosphere. H2 S concentration can vary from several ppm to hundreds of ppm in real sewers. Our understanding of sewer corrosion has increased dramatically in recent years, however, there is limited knowledge of the concrete corrosion at high H2 S levels. This study examined the corrosion development in sewers with high H2 S concentrations. Fresh concrete coupons, manufactured according to sewer pipe standards, were exposed to corrosive conditions in a pilot-scale gravity sewer system with gaseous H2 S at 1100 ± 100 ppm. The corrosion process was continuously monitored by measuring the surface pH, corrosion product composition, corrosion loss and the microbial community. The surface pH of concrete was reduced from 10.5 ± 0.3 to 3.1 ± 0.5 within 20 days and this coincided with a rapid corrosion rate of 3.5 ± 0.3 mm year −1 . Microbial community analysis based on 16S rRNA gene sequencing indicated the absence of sulfide-oxidizing microorganisms in the corrosion layer. The chemical analysis of corrosion products supported the reaction of cement with sulfuric acid formed by the chemical oxidation of H2 S. The rapid corrosion of concrete in the gravity pipe was confirmed to be caused by the chemical oxidation of hydrogen sulfide at high concentrations. This is in contrast to the conventional knowledge that is focused on microbially induced corrosion. This first-ever systematic investigation shows that chemically induced oxidation of H2 S leads to the rapid corrosion of new concrete sewers within a few weeks. These findings contribute novel understanding of in-sewer corrosion processes and hold profound implications for sewer operation and corrosion management. Graphical abstract: Image 1 Highlights: The first report of chemically induced corrosion loss of concrete within 20 days in sewers. H2 S can be chemically oxidized into sulfuric acid on pristine concrete surface. Chemical oxidation of H2 S can reduce the concrete pH to around 3. The rapid concrete corrosion loss was not attributed to sulfide oxidizing microorganisms.