US EPA

3069528 

Journal Article 

Microbiologically assisted stress corrosion cracking in the presence of nitrate reducing bacteria 

Al-Nabulsi, KM; Al-Abbas, FM; Rizk, TY; Salameh, AEM 

2015 

Yes 

Engineering Failure Analysis
ISSN: 1350-6307 

58 

165-172 

10.1016/j.engfailanal.2015.08.003 

WOS:000364916800013 

This study was conducted to establish the root cause of premature cracking failures detected on several firewater hydrants handling untreated seawater. Quantitative polymerase chain reaction (qPCR) was used to characterize the microbial diversity of corrosion products collected from failed structures. In addition, scanning electron microscopy (SEM), coupled with energy dispersive X-ray spectroscopy (EDS) was used to gain insight into the corrosion mechanism. The qPCR results indicated that microbial communities were dominated by nitrate reducing bacteria (NRB) with limited contamination of other corrosion causative microorganisms such as sulfate reducing bacteria (SRB). Fracture examination revealed the effects of two distinctive failure modes: stress corrosion cracking (SCC) and selective leaching (dezincification). SEM examination revealed intergranular corrosion with preferential attack on grain boundaries whereas EDS results confirmed the depletion of zinc on examined fracture surface grains. Environmental cracking of copper alloy C86300 was attributed to ammonia produced by the metabolic activities of nitrate reducing bacteria. (C) 2015 Elsevier Ltd. All rights reserved. 

Nitrate reducing bacteria; DNA; QPCR; Cracking; Fire protection system; Hydrant; Microbially induced corrosion