Effect of Host Media on Microbial Influenced Corrosion due to Desulfotomaculum nigrificans

This article reports about the tests carried to investigate microbial-induced corrosion on stainless steels due to sulfate-reducing bacteria sp. Desulfotomaculum nigrificans in different host media. Stainless steel 304L, 316L, and 2205 were selected for the test. Modified Baar’s media (BM), sodium chloride solution, and artificial sea water (SW) were used as test solutions in anaerobic conditions. Electrochemical polarization and immersion test were performed to estimate the extent of corrosion rate and pitting on stainless steels. SEM/EDS were used to study the details inside/outside pits formed on the corroded samples. Biofilm formed on corroded coupons was analyzed for its components by UV/Visible spectroscopy. Corrosion attack on the test samples was observed maximum in case of exposure to SW followed by NaCl solution, both having sulfide and chloride whereas stainless steel exposed to BM, having sulfide, showed minimum attack. Tendency of extracellular polymeric substances to bind metal ions is observed to be responsible for governing the extent of corrosion attack.     

The Influence of the Desulfovibrio desulfuricans 14 ATCC 27774 on the corrosion of mild steel

The involvement of sulphate‐reducing bacteria (SRB) in microbially influenced corrosion (MIC) of steel and the serious implications associated with their presence in industrial environments have long been known and extensively described. Desulfovibrio desulfuricans ATCC 27774 is an interesting metabolic case of SRB, as it can use both sulphate and nitrate as respiratory substrates during lactate oxidation. This strain has been extensively studied from both a biochemical and structural point of view but, so far, restricted information is available concerning its role in MIC. This work describes a comparative study of the corrosive aggressivity of ATCC 27774 strain towards mild steel when grown either in lactate/sulphate or lactate/nitrate media. The carbon source and electron acceptor's consumption rates were analysed and the metabolic features were correlated with weight loss measurements and SEM observations.     

磷酸钙表面改性镁合金的生物腐蚀性能及细胞相容性(英文)

在镁合金表面制备磷酸钙涂层,利用X射线衍射仪确定涂层的相组成。用扫描电镜观察涂层的微观形貌。结果表明,涂层由板条状的CaHPO4·2H2O晶体组成。采用电化学测试和浸泡实验研究磷酸钙改性镁合金的生物腐蚀性能,并与未改性合金进行对比。通过观察L929细胞在材料表面的粘附生长状况来评价材料的生物相容性。电化学测试结果表明,磷酸钙改性镁合金比未改性合金显示出更好的耐腐蚀性能。浸泡实验表明,磷酸钙涂层可以减缓合金的腐蚀,且在浸泡过程中磷酸钙涂层发生了向羟基磷灰石(HA)的转变。与未改性合金相比,L929细胞在磷酸钙改性镁合金表面显示出良好的粘附、生长和分化特征,表明磷酸钙改性能明显提高基体合金的细胞相容性。     

Fouling and Biocorrosion of a High-Alloy Steel in the Golden Horn Bay

The effect of polluted sea waters of the Golden Horn Bay on the fouling and corrosion of a high-alloyed X18H10T type steel are continued to be investigated. It is shown that the corrosivity of the polluted marine environment increases with the concentration of dissolved oxygen, while that of the control one does with its growing biota determining the biomass and intensity of the metal fouling.     

Biocorrosion of Oil and Gas Field Equipment and Chemical Methods for Its Suppression. I

Main groups of corrosive microorganisms are considered. The parameters of the medium that intensify biocorrosion and the conditions for the formation of biofilms are described. The mechanisms of biocorrosion induced by the main groups of unicellular microorganisms are proposed, and the characteristic types of biodamage, specified.__________Translated from Zashchita Metallov, Vol. 41, No. 4, 2005, pp. 417–426.Original Russian Text Copyright © 2005 by Moiseeva, Kondrova.     

硫酸盐还原菌对低碳钢的腐蚀

本文用失重法测定半连续、不连续培养的硫酸盐还原菌对低碳钢的腐蚀速度,采用线性极化技术测定活性生长的硫酸盐还原菌中低碳钢的线性极化阻力(同时测定自腐蚀电位、菌数、硫化物浓度)随时间的变化,并测量不同电位变化区间的阴阳极恒电位极化曲线。结果表明:在一定Fe2 浓度的硫酸盐还原菌培养基中,硫酸盐还原菌对钢的腐蚀速度与菌的生长时期有密切关系。在活性生长的硫酸盐还原菌系统中一直发生强烈的阴极去极化腐蚀。     

Polarisation of Mild Steel in the Presence of Hydrogen Bacteria and Methane Bacteria

Abstract

The cathodic polarisation behaviour of mild-steel electrodes in a culture of hydrogen bacteria and in methane fermentations has been studied. Negligible cathodic depolarisation was observed and it was concluded that these two groups of bacteria do not participaee significantly in anaerobic microbial corrosion processes.     

Investigation of computer hardware failure due to corrosion

Abstract

Failure analysis was conducted on two failed electronic cardsfrom the Computer Center of the Kuwait Institute for Scientific Research. The results of the elemental analysis indicated that the corrosion product film found on contact pins and soldered through holes was composed of copper and sulphur compounds. Chemical analysis of the air in the computer room indicated a high level of nitrogen oxide (up to 300 ppb), whereas other gases such as H²S and SO² were below the detectahle limits (100 and 200 ppb respectively) of the analytical technique used. It was concluded that the initial high relative humidity ( ～ 75%) had synergised with the strongly oxidising nitrogen oxide and H²S and/or SO² to bring about the corrosion of copper substrate in ‘bare spots’ or gaps in the soldered contacts, causing card failure. Other factors, such as galvanic coupling of the copper substrate with nickel, silver, and gold plates, and the relatively high local temperature, may have accelerated the corrosion process. A decrease in the relative humidity to the optimum value of 45% did not obviate card failure. It was concluded that efficient air filters should be utilised in the computer environment, as electronic equipment can be damaged by levels of pollutant gases 10 times lower than those cited for human safety requirements.     

Evolution of reinforcement corrosion due to climatic variations

Concrete moisture is the most significant parameter with respect to its durability, however the data on moisture content in real‐size structures are scarce in contrast to the numerous literature published on laboratory experiments. The majority of laboratory tests have been performed in chambers with controlled hydrothermal regime, in general to enable the concrete to reach equilibrium and steady‐state conditions. However, real weather induces permanent non‐steady state situations due to the evolution of temperature and climatic events as snowing or raining. Present paper discusses the effect of climatic events on the hydrothermal performance of concrete and their influence on reinforcement corrosion process. Concerning the moisture level, the degree of saturation, S_W, and not the internal relative humidity has been identified to be the controlling parameter of the corrosion process. The psychometric chart and the S_W‐RH plots are very suitable to study the hydrothermal behaviour. With respect to the corrosion parameters, corrosion potential, resistivity and corrosion rates, they are very influenced by temperature in a complex manner. The temperature is the main factor influencing the degree of saturation in sheltered conditions while rain and snow are so, in unsheltered ones. In opposition, however, what can be expected, climates with higher temperatures are less aggressive than colder ones, except when rain periods are produced during the hotter periods.     

Corrosion of steels due to the action of microorganisms

The susceptibility of variously alloyed structural steels to microbiological corrosion in media enriched with hydrogen sulfide and favorable for reproduction of sulfate-reducing bacteria is studied. It is shown that stainless steels 05Kh17N4DB and especially nitrogen-alloyed steel 05Kh13A possess a higher anti-adhesive capacity with respect to corrosion-active microorganisms and resistance to microbe fouling and formation of corrosion-active biofilms than the conventional structural steel 38KhGM. It is assumed that the action of nitrogen can be connected with formation of biocide substances.     

Analysis of pits induced stresses due to metal corrosion

The corrosion damage due to pitting is commonly observed in a wide range of aluminum alloys and structural steels that are being used for aerospace and naval structural applications. In order to predict the nucleation of cracks resulting from nucleation and growth of pits, there is a need to obtain the stress environment around pits. The objective of this study is to investigate the pits induced stresses responsible for possible crack nucleation using the photomicrographs of corroded aluminum 5059 alloy samples using stress analysis. An analysis procedure is developed using CAD and finite element analysis to predict stresses due to single and/or multiple corroded pits. The analysis was performed to investigate stress distributions on the corrosion surface as a function of sensitization time. The results obtained indicate that as the duration of the specimen sensitization increased from 50 days to 74 days, the highest stress levels have increased by about 56%. However, further increase in the sensitization time from 74 to 100 days has very little effect on the stress level. The observed severe exfoliation or the tearing of the sample surface layers in and around the pits is due to the nucleation and coalescence of fine cracks. The cracks are nucleated because of the production and the buildup of differential stresses along the sample thickness.     

Hardening of a bismuth crystal due to electroplastic deformation

The surface texture of a bismuth crystal after deformation of the surface by a diamond pyramid and simultaneous passage of a pulse of high-density electric current is studied. The fact of hardening is established by measuring the microhardness in the zone of the indentation. __________ Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 3, pp. 54–56, March, 2007.     

Failure of crude oil pipeline due to microbiologically induced corrosion

Abstract

A 25·5 km long and 28 in. diameter underground pipeline used for transporting wet sour Arab Light grade crude oil failed after 3 years of service. The pipeline was operated at 40% of permissible flow velocity and capacity and protected under a corrosion inhibitor programme. The failure occurred due to corrosion of the lower surface of the pipeline resulting in pinholes within a period of one month. Eight corrosion damaged areas were detected over the entire length of the pipeline. Ultrasonic non-destructive inspection and close potential surveys were conducted on the failed pipeline. Various sections of the corrosion products were metallurgically evaluated using scanning electron microscopy coupled with energy dispersive X-ray spectroscopy. The corrosion product was identified using photometric and potentiometric analysis combined with X-ray diffraction. Crude oil and water samples obtained from the pipeline were also analysed. The material of the pipeline was identified as AISI grade C1018. Ultrasound testing revealed localised pitting at failed locations, while close potential surveys ruled out external corrosion. Experimental results indicated that the failure was caused by extensive microbiologically induced corrosion at the internal surface of the pipeline. Sulphate reducing bacteria present in the crude oil, along with below standard flow velocity of the latter, is thought to be responsible for the observed microbiologically induced corrosion. Replacement with a 20 in. diameter pipeline was suggested as a permanent solution to the corrosion problem, whereas a number of short-term measures were also recommended.     

Phase-field simulation of abnormal grain growth due to inverse pinning

The possibility of abnormal grain growth due to inverse pinning was verified using phase-field simulations. In bicrystalline systems with circular precipitates, the perfect wetting condition is required for the long-distance migration of the interface between the matrix grains. If the distance between precipitates that are perpendicular to the interface exceeds a critical value, the migration is not observed irrespective of the wetting condition. In polycrystalline systems, abnormal grain growth occurs with the aid of the driving force for grain growth even though l_lim exceeded the critical value, where l_lim is the minimum distance between precipitates. Furthermore, the perfect wetting condition is not required for the abnormal grain growth in the polycrystalline systems. These facts enlarge the possibility of inverse pinning in real alloy systems.     

Failure of cross-rolled beryllium plates due to a point load

Failure prediction of cross-rolled beryllium SR-200 sheets loaded in a complex state of stress was demonstrated by means of the Tsai-Wu failure theory. A total of sixteen beryllium plates, 2.54 mm thick with various length-to-width ratios and support conditions, were tested in the laboratory with a central transverse point load. Finite-element analyses of the plates were coupled with the failure prediction theory. Prediction of failure from numerical simulation was compared with strain gage and displacement transducer measurements. Analysis of the load history of the specimens revealed a primary and an ultimate failure load. Ultimate failure of a fully clamped plate caused an unusual delamination phenomenon, whereby a circular region displaced in the direction of the load, but did not separate from the plate.     

Growth texture due to directed crystallization of high-temperature nickel alloys

Processes of formation of growth texture [001] due to directed crystallization of high-temperature nickel alloys are considered and their qualitative and quantitative characteristics determined. Simulation of competitive growth is performed for flat bicrystal ingots. __________ Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 8, pp. 25–32, August, 2006.     

Damage evolution in cement mortar due to erosion of sulphate

Ultrasonic technique is used to detect the velocity change of stress wave propagated in the cement mortar immersed in the solution of sodium sulfate for 425 days. Also the density change of specimens at different erosion time is measured. By curve fitting, the effect of solutions’ concentration and water/cement ratio on the damage evolution is analyzed. The SEM observation on the growth of delayed ettringite is also performed. It shows that the damage evolution of specimens attacked by sulphate solution is dominantly induced by the nucleation and growth of delayed ettringite, and the average size of microvoids in cement mortar affects the damage evolution significantly.     

Studies on leaching of metals from solders due to corrosion

Leaching of Ag, Cd, Cu, Pb, Sn, Sb and Zn from 50/50 Pb/Sn, 95/5 Sn/Sb and 96/4 Sn/Ag soldered copper plates into distilled, tap and well waters as a function of contact time under static conditions was done. Ag, Cd and Sb were not leached to significant extent. Significant amounts of tin were leached especially into tap and well waters. The amount of copper leached from soldered samples was in general less than the amount leached from blank copper samples. The amount of Zn leached was by far less than the drinking water quality limit (5 mg/L). The amount of Pb leached from nonleaded solders was less than 10 μg/L and exceeded 10 μg/L in the case of Pb/Sn solder. Surface analysis by X-ray photoelectron spectroscopy and electron microprobe techniques of Pb/Sn solder samples showed the presence of Pb and Sn oxides. The results fit into galvanic corrosion scheme of the solder surface.