The corrosion behaviour of galvanized steel in cooling tower water containing a biocide and a corrosion inhibitor

The corrosion behaviour of galvanized steel in cooling tower water containing a biocide and a corrosion inhibitor was investigated over a 10-month period in a hotel. Planktonic and sessile numbers of sulphate reducing bacteria (SRB) and heterotrophic bacteria were monitored. The corrosion rate was determined by the weight loss method. The corrosion products were analyzed by energy dispersive X-ray spectroscopy and X-ray diffraction. A mineralized, heterogeneous biofilm was observed on the coupons. Although a biocide and a corrosion inhibitor were regularly added to the cooling water, the results showed that microorganisms, such as SRB in the mixed species biofilm, caused corrosion of galvanized steel. It was observed that Zn layers on the test coupons were completely depleted after 3?months. The Fe concentrations in the biofilm showed significant correlations with the weight loss and carbohydrate concentration (respectively, p?<?0.01 and p?<?0.01).     

Influence of an oil soluble inhibitor on microbiologically influenced corrosion in a diesel transporting pipeline

Abstract

Microbial degradation of the oil soluble corrosion inhibitor (OSCI) Baker NC 351 contributed to a decrease in inhibitor efficiency. Corrosion inhibition efficiency was studied by the rotating cage and flow loop methods. The nature of the biodegradation of the corrosion inhibitor was also analysed using Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy and gas chromatography-mass spectrometry. The influence of bacterial activity on the degradation of the corrosion inhibitor and its influence on corrosion of API 5LX were evaluated using a weight loss technique and impedance studies. Serratia marcescens ACE2 and Bacillus cereus ACE4 can degrade aromatic and aliphatic hydrocarbons present in the corrosion inhibitor. The present study also discusses the demerits of the oil soluble corrosion inhibitors used in petroleum product pipeline.     

Control of biocorrosion using laboratory and field assessments

Biofouling and biocorrosion can be significant problems in oilfield water injection systems, despite extensive use of chemical biocides. This work set out to establish relevant testing and monitoring procedures to optimise microbiological control in these systems.A combination of laboratory based sessile biocide screening trials and onsite monitoring of biofilm bacteria was developed to ensure that an effective biocontrol programme was set up. It is important to use a mixed population of bacteria freshly isolated from biofilms in the system to ensure that any biocide tolerance of the system bacteria is reflected in the laboratory tests. In general, the results are borne out by the site audits of the control regime against sessile bacteria in the system.In an industrial system, biocide resistant populations develop from time to time. In practice it was found that even a small change to the biocide formulation could improve biocontrol, with concomitant reduction in corrosion rates and maintenance costs.     

Fouling and corrosion in an open recirculating cooling system

The paper discusses the problem of fouling and corrosion in the Service Water System of a nuclear reactor employing an open recirculating cooling system. Field and laboratory experiments were carried out using carbon steel as test material. The studies included corrosion rate measurements, corrosion product characterisation (using XRD, EDAX and IRAS), and the effects of addition of biocide (chlorine) and corrosion inhibitor (polyphosphates) on the bacterial population of the cooling water. The fouling films which developed on metal and glass coupons as well as debris collected from within the cooling system were chemically characterised. The results indicated the prevalence of microbiologically induced corrosion (MIC) within the system. The findings are discussed in the light of the information available on MIC of cooling water systems.     

Variation in sessile microflora as function of flow velocity on coupons exposed to seawater

The variability of several groups of microorganisms on AISI 1020 carbon steel coupons as a function of seawater velocity in a water circulation loop was investigated. The metal probes as well as electrodes were fixed onto ducts connected to a 35l capacity tank, in order to study both biofilm formation and some electrochemical parameters. The experiments were carried out at different seawater velocities. The technique of the most probable number was used to enumerate bacterial aerobes and anaerobes as well as sulphate-reducing bacteria and iron-reducing bacteria. Fungi were quantified by counting the number of colony forming units. At velocities of 3.6 cm/s, which correspond to a laminar flow, the numbers of aerobic and anaerobic bacteria attached to the metal surfaces reached a maximum. Such values were markedly reduced at velocities of 17.4–26.0 and 34.8 cm/s. The corrosion rate at the start of the process was 1.4 mm/year, decaying to levels of about 0.4–0.6 mm/year over the experimental period. Analysis of loss of carbon steel coupons mass after 35 days of the process indicated a mean corrosion rate of approximately 2 mm/year. This revised version was published online in November 2006 with corrections to the Cover Date.     

Influence of an oil soluble inhibitor on microbiologically influenced corrosion in a diesel transporting pipeline

Microbial degradation of the oil soluble corrosion inhibitor (OSCI) Baker NC 351 contributed to a decrease in inhibitor efficiency. Corrosion inhibition efficiency was studied by the rotating cage and flow loop methods. The nature of the biodegradation of the corrosion inhibitor was also analysed using Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy and gas chromatography-mass spectrometry. The influence of bacterial activity on the degradation of the corrosion inhibitor and its influence on corrosion of API 5LX were evaluated using a weight loss technique and impedance studies. Serratia marcescens ACE2 and Bacillus cereus ACE4 can degrade aromatic and aliphatic hydrocarbons present in the corrosion inhibitor. The present study also discusses the demerits of the oil soluble corrosion inhibitors used in petroleum product pipeline.     

Biodegradation of corrosion inhibitors and their influence on petroleum product pipeline

The present study enlightens the role of Bacillus cereus ACE4 on biodegradation of commercial corrosion inhibitors (CCI) and the corrosion process on API 5LX steel. Bacillus cereus ACE4, a dominant facultative aerobic species was identified by 16S rDNA sequence analysis, which was isolated from the corrosion products of refined diesel-transporting pipeline in North West India. The effect of CCI on the growth of bacterium and its corrosion inhibition efficiency were investigated. Corrosion inhibition efficiency was studied by rotating cage test and the nature of biodegradation of corrosion inhibitors was also analyzed. This isolate has the capacity to degrade the aromatic and aliphatic hydrocarbon present in the corrosion inhibitors. The degraded products of corrosion inhibitors and bacterial activity determine the electrochemical behavior of API 5LX steel.     

60Coγ射线引发聚合的丙烯酸共聚物阻垢缓蚀剂性能研究

采用60Coγ射线引发聚合制备了丙烯酸共聚物阻垢缓蚀剂,考察了该阻垢缓蚀剂与国内同类产品在不同环境条件下的阻垢率和缓蚀率,实验表明：该阻垢缓蚀剂具有耐高温,耐碱的优点,阻垢和缓蚀性能优于国内同类产品;经过半年的工业现场应用试验,取得了很好的效果.     

A synergistic d-tyrosine and tetrakis hydroxymethyl phosphonium sulfate biocide combination for the mitigation of an SRB biofilm

Microbiologically influenced corrosion (MIC) is a major problem in various industries such as oil and gas, and water utilities. Billions of dollars are lost to microbiologically influenced corrosion (MIC) each year in the US. The key to MIC control is biofilm mitigation. Sulfate-reducing bacteria (SRB) are often the culprits. They are also involved in souring and biofouling. SRB biofilms are notoriously difficult to eradicate. Due to environmental concerns and increasing costs, better biocide treatment strategies are desired. Recent studies suggested that D: -tyrosine and some other D: -amino acids may signal biofilm dispersal. Experimental results in this work indicated that D: -tyrosine is an effective biocide enhancer for tetrakis hydroxymethyl phosphonium sulfate (THPS) that is a green biocide. Desulfovibrio vulgaris (ATCC 7757) was used in biofilm prevention and biofilm removal tests. It was found that 100?ppm D: -tyrosine alone and 50?ppm THPS alone were both ineffective against the SRB biofilm. However, when 1?ppm D: -tyrosine was combined with 50?ppm THPS, the synergy between the two chemicals successfully prevented the establishment of the SRB biofilm on C1018 mild steel coupon surfaces in batch treatment tests. It also eradicated established SRB biofilms from coupon surfaces in both 1 and 3-h shock treatment tests.     

Evaluation of water corrosion,scaling extent and heterotrophic plate count bacteria in asbestos and polyethylene pipes in drinking water distribution system

Corrosion and scaling is one of the most important factors influencing drinking water quality that cause health disorders and economic problems. The aim of this study was to evaluate these phenomena in two sources of surface (Makou city) and ground water (Khoy city) in water networks. Corrosion and scaling potential was surveyed by Langelier, Ryzener, aggressiveness, Larson and Puckorius Indices and with measuring water physical, chemical, and microbial parameters. Statistical paired samples t-test displayed significant difference in means value of Langelier, Ryzener, Puckorius indices between cold and warm seasons of the year in Khoy samples and significant difference in means value of Ryzener, Puckorius and aggressiveness indices between cold and warm seasons of the year in Makou samples (p-value <0.001). Heterotrophic plate count water samples investigated in two cold and hot seasons in Khoy were respectively 14 ± 16 cfu ml^?1 and 41 ± 26 cfu ml^?1 and in the town of Makou were 11 ± 7 cfu ml^?1 and 61 ± 29 cfu ml^?1, respectively. In terms of health impacts, corrosion in different mains is important, then providing proper measures for balancing water quality before entering to the network and substituting of mains to prevent economic and health problems are necessary.     

An assessment of the early stages of microfouling and corrosion of 70:30 copper nickel alloy in the presence of two marine bacteria

The early stages of bacterial settlement on 70:30 copper nickel alloy was followed by scanning electron microsocopy. Two strains of marine bacteria (Pseudomonas sp and Vibrio alginolyticus) isolated from polluted harbour sea water were used. The corrosion behaviour of the alloy was studied through corrosion potential measurements made in sterile and contaminated sea water. According to our results microbial colonisation of the metal surface occurs within the first 24 h for the two bacteria used. Well defined microbial colonies with localised corrosion underneath were seen by SEM after short periods of exposure. Corrosion attack seems to be closely related to passive film modification by the bacterial settlement.     

Substrate Availability,pH, and Temperature Influence Methanogenesis and Mild Steel Corrosion

Solid deposits of corroded pipelines in the Niger Delta were analyzed both chemically and microbiologically. The addition of substrate, especially acetate, significantly stimulated the methane production ranging from 0.85 to 1.60 mmole compared with 0.65 mmole of the control. Acetotrophic and hydrogenotrophic methanogens had their optimal methane production and corrosion rate at pH 5.5. All three types of methanogens produced the most methane at 37°C. Methane production by methanogens correlated strongly with corrosion rate. Pyrosequencing surveys show dominance of acetotrophic, hydrogenotrophic, and methylotrophic methanogens in the samples with no significant presence of sulfate-reducing bacteria (SRB), most likely due to the presence of the biocide, tetrakis-hydroxymethyl phosphonium sulfate. Our study shows that methanogens were one possible cause of pipeline failures in samples from the Niger Delta without the syntrophic association with SRB.     

Importance of biofilm formation for corrosion inhibition of SAE 1018 steel by axenic aerobic biofilms

To investigate if corrosion inhibition by aerobic biofilms is a general phenomenon, carbon steel (SAE 1018) coupons were exposed to a complex liquid medium (Luria–Bertani) and seawater-mimicking medium (VNSS) containing fifteen different pure-culture bacterial suspensions representing seven genera. Compared to sterile controls, the mass loss in the presence of these bacteria (which are capable of developing a biofilm to various degrees) decreased by 2- to 15-fold. The extent of corrosion inhibition in LB medium depended on the nature of the biofilm: an increased proportion of live cells, observed with confocal scanning laser microscopy (CSLM) and image analysis, decreased corrosion. Corrosion inhibition in LB medium was greatest with Pseudomonas putida (good biofilm formation), while metal coupons exposed to Streptomyces lividans in LB medium (poor biofilm formation) corroded in a manner similar to the sterile controls. Pseudomonas mendocina KR1 reduced corrosion the most in VNSS. It appears that only a small layer of active, respiring cells is required to inhibit corrosion, and the corrosion inhibition observed is due to the attached biofilm. Received 09 December 1996/ Accepted in revised form 19 March 1997     

Antimicrobial effect of tetramethyldithiooxamide and its application as a biocide

Tetramethyldithiooxamide (TMDTOA) is a stable and effective inhibitor of metal corrosion. The antimicrobial effects of TMDTOA and its metal compounds were investigated with regard to their use as biocides for water treatment. Growth of a variety of strains of bacteria and yeasts was completely inhibited at 400 υmol 1⁻¹ TMDTOA or its metal complexes. At 100 mg 1⁻¹ there was a 99·99% reduction in the number of viable micro-organisms; this activity persisted for 1–3 months. TMDTOA can be produced cheaply at 98% purity by a novel method, representing an alternative cost-effective water treatment agent combining corrosion-inhibiting and biocide characteristics.     

Sulphide production and corrosion in seawaters during exposure to FAME diesel

Experiments were designed to evaluate the corrosion-related consequences of storing/transporting fatty acid methyl ester (FAME) alternative diesel fuel in contact with natural seawater. Coastal Key West, FL (KW), and Persian Gulf (PG) seawaters, representing an oligotrophic and a more organic- and inorganic mineral-rich environment, respectively, were used in 60 day incubations with unprotected carbon steel. The original microflora of the two seawaters were similar with respect to major taxonomic groups but with markedly different species. After exposure to FAME diesel, the microflora of the waters changed substantially, with Clostridiales (Firmicutes) becoming dominant in both. Despite low numbers of sulphate-reducing bacteria in the original waters and after FAME diesel exposure, sulphide levels and corrosion increased markedly due to microbial sulphide production. Corrosion morphology was in the form of isolated pits surrounded by an intact, passive surface with the deepest pits associated with the fuel/seawater interface in the KW exposure. In the presence of FAME diesel, the highest corrosion rates measured by linear polarization occurred in the KW exposure correlating with significantly higher concentrations of sulphur and chlorine (presumed sulphide and chloride, respectively) in the corrosion products.     

Biofilm formation on copper and its control by inhibitor/biocide in cooling water environment

The present study has successfully identified the nitrate reducing bacteria present in the cooling water system and also investigated the performance of industrially applied biocide and inhibitor on the bacterial inhibition. In order to carry out the objective of this study, facilities and methods such as 16S rRNA gene sequencing, Lowry assay, SEM, EIS, ICP-MS and weight loss analysis were being utilized. In this study, two out of the five morphologically dis- similar colonies identified through 16S rRNA gene sequencing, namely the Massilia timonae and the Pseudomonas, were being utilized in the biocorrosion study on copper metal. From the surface analysis using SEM demonstrated the phenomenon of biofilm formation on the copper surface. 2-methylbenzimidazole has the addition of methyl group in the diazole ring position of benzimidazole it has create basicity environment and inhibit the metal deterioration. Meanwhile, it is also deducible from the EIS and protein analysis that com- bination of biocide with either of the inhibitors gives rise to better biocorrosion suppression (0.00178 mpy and 0.00171mpy) as compared to the sole effect of either biocide or inhibitor (0.00219 mpy, 0.00162 and 0.00143). Biocorrosion system biocide with MBM was found to exhibit 65% corrosion inhibition efficiency. Moreover, adoption of 2-Methylbenzimidazole seems to display better performance as compared to Multionic 8151, which is adopted in cooling water system.     

A green triple biocide cocktail consisting of a biocide, EDDS and methanol for the mitigation of planktonic and sessile sulfate-reducing bacteria

Sulfate-reducing bacteria (SRB) cause souring and their biofilms are often the culprit in Microbiologically Influenced Corrosion (MIC). The two most common green biocides for SRB treatment are tetrakis-hydroxymethylphosphonium sulfate (THPS) and glutaraldehyde. It is unlikely that there will be another equally effective green biocide in the market any time soon. This means more effective biocide treatment probably will rely on biocide cocktails. In this work a triple biocide cocktail consisting of glutaraldehyde or THPS, ethylenediaminedisuccinate (EDDS) and methanol was used to treat planktonic SRB and to remove established SRB biofilms. Desulfovibrio vulgaris (ATCC 7757), a corrosive SRB was used as an example in the tests. Laboratory results indicated that with the addition of 10–15% (v/v) methanol to the glutaraldehyde and EDDS double combination, mitigation of planktonic SRB growth in ATCC 1249 medium and a diluted medium turned from inhibition to a kill effect while the chelator dosage was cut from 2,000 to 1,000 ppm. Biofilm removal was achieved when 50 ppm glutaraldehyde combined with 15% methanol and 1,000 ppm EDDS was used. THPS showed similar effects when it was used to replace glutaraldehyde in the triple biocide cocktail to treat planktonic SRB.     

Biodegradation and corrosion behaviour of <Emphasis Type="Italic">Serratia marcescens</Emphasis> ACE2 isolated from an Indian diesel-transporting pipeline

A facultative anaerobic species Serratia marcescens ACE2 isolated from the corrosion products of a diesel-transporting pipeline in North West India was identified by 16S rDNA sequence analysis. The role of Serratia marcesens ACE2 on biodegradation of commercial corrosion inhibitor (CCI) and its influence on the corrosion of API 5LX steel has been enlightened. The degrading strain ACE2 is involved in the process of corrosion of steel API 5LX and also utilizes the inhibitor as organic source. The quantitative biodegradation efficiency of corrosion inhibitor was 58%, which was calculated by gas chromatography mass spectrum analysis. The effect of CCI on the growth of bacteria and its corrosion inhibition efficiency were investigated. Additionally, the role of this bacterium in corrosion of steel has been investigated by powder X-ray diffractometer (XRD) and scanning electron microscope studies. The presence of high-intensity ferric oxides and manganese oxides noticed from the XRD indicates that ACE2 enhances the corrosion process in presence of inhibitor as a carbon source. This basic study will be useful for the development of new approaches for the detection, monitoring and control of microbial corrosion in petroleum product pipelines.     

不同生态系统对湘西洛塔降雨量及岩溶效应的影响

采用雨量器、滤膜法、CO2气体监测管法、标准试片对湘西洛塔不同生态系统降雨量、泥沙量、土壤CO2浓度、溶蚀速度进行了研究。结果表明:森林生态系统降雨量高于灌丛生态系统,观测第一年高6.84mm,第二年高218.08mm,且时间趋向均匀;灌丛生态系统水土流失严重,其泥沙含量是森林生态系统的1.53倍,土壤侵蚀为强度,而森林生态系统为微度;不同深度土壤CO2浓度在森林和灌丛生态系统中具有相同的变化趋势,在春季、秋季、冬季随土层加深而增大,在夏季,随土层加深先减少后增大,但季节变化动态略有差异,森林生态系统不同深度、不同季节土壤CO2浓度均大于灌丛生态系统;从全年土壤CO2浓度对比来看,10、20、40cm处,森林生态系统分别是灌丛生态系统的1.66、1.59和1.90倍;不同深度上,溶蚀速度在森林和灌丛生态系统具有相同的变化趋势,15cm处均大于地面,从同一深度来看,森林生态系统溶蚀速度均大于灌丛生态系统,地面、15cm处溶蚀速度分别是灌丛生态系统的1.11倍、2.57倍,说明森林生态系统具有较好的岩溶效应。     

微生物腐蚀及腐蚀机理研究进展

在不同的环境中,不同种类的微生物能在材料上附着繁殖,其生命活动会引起或加剧材料的腐蚀。根据种类及功能的不同,腐蚀微生物可以分为硫酸盐还原菌、硫氧化菌、产酸菌、铁氧化细菌、铁还原细菌、硝酸盐还原菌以及产粘液细菌等。微生物腐蚀几乎能使所有现用的材料受到严重影响,破坏材料的结构与性能,在建筑、运输管道、工业环境(石油化工等)以及海洋环境中造成巨大的安全隐患和财产损失。本文概述了目前发现的腐蚀相关微生物的类群和特性,以及相对应的微生物腐蚀机理,为防护和控制材料的微生物腐蚀提供理论指导。