Materials Performance

JUN 2016

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.

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40 JUNE 2016 MATERIALS PERFORMANCE NACE INTERNATIONAL: VOL. 55, NO. 6 COATINGS & LININGS ESSENTIALS D C I s o l a t i o n • A C G r o u n d i n g O v e r - Vo l t a g e P r o t e c t i o n GIVING AWAY FREE CP CURRENT • Fail-Safe & Maintenance Free Products • Simultanious CP Isolation & Safety Grounding • Lightning Protection Rated • Impeccable Product Performance for More than 30 years • UL, C-UL Certifications for grounding electrical equipment • UL, C-UL Certifications for hazardous locations • IECEx and ATEX certified Continued on page 42 Research Investigates Coating Failures from Microbial Activity Fusion-bonded epoxy (FBE) coatings can fail due to cathodic corrosion, disbonding, improper application, or improper curing, and these failure mechanisms are fre- quently investigated as the root causes. Rarely is microbial activity considered, even though microorganisms can degrade bi- sphenol, a component of FBE coatings. In one case involving an FBE coating, MIC was ruled out due to the length of time it took for the microorganisms to grow, and the fact that the microbes only grew in a small number of samples. Research of coating failures by the wastewater industry, how- ever, has demonstrated that microorgan- isms can corrode concrete sewers and other protective surfaces such as concrete linings, cement-based coatings, and epoxy-mortar coatings. A FBE-coated coupon with a biofilm when removed from a bioreactor after 80 days. Te lack of research on the microbial impact on pipeline coating failures leaves a signifcant knowledge gap. Traditionally, corrosion-causing microorganisms are detected and quantifed with microbial growth tests in diferent enrichment media. Te traditional growth method (Most Prob- able Number [MPN] test) often relies on liquid samples containing live microbes, and it can take up to four weeks to obtain the results. Unfortunately, only 0.1 to 10% of microorganisms in an environmental sam- ple can grow in artifcial media, and a sig- nifcant portion of microbes growing in the media are not target microbes. For this reason, growth-based tests are often unable to provide an accurate quantifcation of target microorganisms in samples. In CORROSION 2016 paper no. 7335, "Te Impact of Microbial Activity on Infra- structure Pipeline Coatings," by A. Reese, A. Harmon, K. Crippen, and A. Darzins, the authors discuss their analysis of the corro- sion of coated samples with a bioflm. Tey were analyzing FBE coating samples from the external surfaces of two buried steel transmission pipelines with unusually rapid external pitting. One pipeline was so newly constructed that cathodic protection (CP) had not yet been installed. Nevertheless, it developed a deep pit (80%) in less than a year. Te other pipeline had CP, but

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