Materials Performance

NOV 2017

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

Issue link: http://mp.epubxp.com/i/889936

Contents of this Issue

Navigation

Page 17 of 84

15 NACE INTERNATIONAL: VOL. 56, NO. 11 MATERIALS PERFORMANCE NOVEMBER 2017 MIC manifested as localized pitting of the steel piling on several of the piers. Photo courtesy of Ali Abu-Yosef, Pivot Engineers. Continued on page 16 762 mm]. What we had here was widespread pitting damage cover- ing large portions of the piles. The fact that it covered a large por- tion of the pile was sur- prising for us." The soil samples collected for MIC cul- ture testing showed high levels of acid-pro- ducing bacteria (A PB) and the presence of sul- fate-reducing bacteria (SRB). Meanwhile, half- cell potentials taken showed a 450 mV dif- ference between the ash and clay layers, with the most negative values recorded near the failure zone. As such, this indi- cated the environment around the piles was suitable for the formation of a macro- cell corrosion mechanism. "You have two different mediums, f ly ash and clay, that have very different characterizations," Abu-Yosef explains. "That would promote macrocell [corro- sion] by itself. Then the presence of the microbes promoted additional corrosion activity. What MIC did is lower the pH further on the face of the pile, which led to rapid loss in the steel section." The most severe corrosion was found in a 4-ft (1.2-m) long area located below the water line at the interface of the two soil layers. The corrosion and material loss from the affected piles then led to severe deterioration, crushing, and buck- ling on the remaining piles. "It was very unique," says Abu-Yosef, who delivered a presentation 2 on his experience at the NACE Central Area Conference in August 2017. "You would rarely see instances where you see multi- ple mechanisms competing with each other and making the situation signif i- cantly worse. The conditions around the piles, which helped promote two different mechanisms to work together to bring the bridge down, is something really unique. Even for people that had done this work for 30 years, they were surprised." According to Abu-Yosef, design codes have not changed since the initial con- struction of the bridge in 1981, and prior inspections had shown the bridge to be compliant. "The inspection state-of- practice does not include assessment of piles," he says. "What an inspector would do is visually inspect the structural elements in the superstructure, and every thing below the ground is rarely done in practice. FarwestCorrosion.com Anodes Rectifiers Reference Electrodes AC Mitigation Remote Monitoring Backfill Test Stations Coatings Isolators Test Instruments C.P. Installation C.P. Technical Services 9 LOCATIONS NATIONWIDE 888-532-7937 Anodes Rectifiers Reference Electrodes AC Mitigation Remote Monitoring Backfill Test Stations Coatings Isolators Test Instruments C.P. Installation C.P. Technical Services 9 LOCATIONS NATIONWIDE 888-532-7937 CATHODIC PROTECTION & CORROSION CONTROL SOLUTIONS & SERVICES CATHODIC PROTECTION & CORROSION CONTROL SOLUTIONS & SERVICES Information on corrosion control and prevention A section of the Leo Frigo Memorial Bridge dipped in September 2013 after corrosion of a supporting pier. Photo courtesy of WisDOT.

Articles in this issue

Links on this page

Archives of this issue

view archives of Materials Performance - NOV 2017