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51317--9650-Effect of Biocides and Corrosion Inhibitors On SRB-Mediated MIC Under Flow Conditions

Biocides and corrosion inhibitors can decrease corrosion in stagnant and flowing systems. We used 1 ml syringe columns packed with 60 carbon steel beads (55 mg each), which were continuously injected with the effluent of an sulfur reducing bacteria continuous culture chemostat, to monitor corrosion under flow conditions.

Product Number: 51317--9650-SG
ISBN: 9650 2017 CP
Author: Gerrit Voordouw
Publication Date: 2017
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Biocides and corrosion inhibitors are used to prevent corrosion in stagnant and flowing systems like storage tanks and pipelines respectively. We have used 1 ml syringe columns packed with 60 carbon steel beads (55 mg each) which were continuously injected with the effluent of an SRB continuous culture chemostat to monitor corrosion under flow conditions. A constant flow rate of 0.5 ml/hr was maintained throughout. General corrosion rates (CRs) were determined after 45 days of flow by measuring the weight loss of acid-treated beads. Medium entering the chemostat contained sulfate (10 mM) as electron acceptor and either formate (20 mM) or lactate (10 mM) as electron donor for the growth of SRB. Medium with formate and sulfate also contained 1 mM acetate as a carbon source. Effluent of the chemostat with 5 mM sulfate 5 mM sulfide and high numbers of SRB in both cases was then continuously injected into the syringe columns. CRs of beads in these columns were higher with formate and sulfate (0.1 mm/yr) than with lactate and sulfate (0.02 mm/yr). Periodic biocide treatment (2 h of 300 ppm every 4 days at the same flow rate) decreased CRs on average by 35% indicating modest success to control corrosion in a system which is continuously flooded with freshly grown SRB. In contrast a single exposure of the carbon steel beads to a corrosion inhibitor at the start of the experiment decreased CR by 98% to 0.002 mm/yr Hence although periodic biocide treatment of carbon steel in pipelines receiving a constant influx of new bacteria may give a temporary kill this may not afford the same degree of corrosion control as obtained with a corrosion inhibitor.

Keywords: biocides, corrosion inhibitors, SRB, chemostat, corrosion rates

Biocides and corrosion inhibitors are used to prevent corrosion in stagnant and flowing systems like storage tanks and pipelines respectively. We have used 1 ml syringe columns packed with 60 carbon steel beads (55 mg each) which were continuously injected with the effluent of an SRB continuous culture chemostat to monitor corrosion under flow conditions. A constant flow rate of 0.5 ml/hr was maintained throughout. General corrosion rates (CRs) were determined after 45 days of flow by measuring the weight loss of acid-treated beads. Medium entering the chemostat contained sulfate (10 mM) as electron acceptor and either formate (20 mM) or lactate (10 mM) as electron donor for the growth of SRB. Medium with formate and sulfate also contained 1 mM acetate as a carbon source. Effluent of the chemostat with 5 mM sulfate 5 mM sulfide and high numbers of SRB in both cases was then continuously injected into the syringe columns. CRs of beads in these columns were higher with formate and sulfate (0.1 mm/yr) than with lactate and sulfate (0.02 mm/yr). Periodic biocide treatment (2 h of 300 ppm every 4 days at the same flow rate) decreased CRs on average by 35% indicating modest success to control corrosion in a system which is continuously flooded with freshly grown SRB. In contrast a single exposure of the carbon steel beads to a corrosion inhibitor at the start of the experiment decreased CR by 98% to 0.002 mm/yr Hence although periodic biocide treatment of carbon steel in pipelines receiving a constant influx of new bacteria may give a temporary kill this may not afford the same degree of corrosion control as obtained with a corrosion inhibitor.

Keywords: biocides, corrosion inhibitors, SRB, chemostat, corrosion rates

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