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Determination of causes of accelerated local corrosion of austenitic steels in water supply systems
... The presence of chloride ions in naturally or brackish groundwater and historical geological sea beds, or as a source of salt from road services to sprinkle roads in urbanized areas, indicates that soil resistivity is decreasing. According to some studies 53 , up to 50% of salt penetrates locally to surface water 54 , and the content of chloride ions in some soils can reach up to 2700 mg/l 55 . Sulfate is another corrosive chemical substance whose presence poses a significant risk to metallic pipes because it is chemically harmful and highly corrosive, and it can be converted directly to sulfides by anaerobic SRB. ...
... In ref. 90 , a damaged external protective coating of a steel pipeline caused by a sharp object (such as stones) from the improper installation can cause dents and, eventually, corrosion problems. Jacek Ryl et al. 53 , indicated that while building a new road and removing the surface of the old one, the pipeline may be exposed to overload and other factors, which can be a motivator for corrosion to occur. Furthermore, human errors can occur during manufacturing, such as irregular mortar coating thickness, inconsistent prestressing wire spacing, and low mortar quality, as stated in ref. 91 . ...
Corrosion is still the most common contributor to failures in Water Distribution Networks (WDNs), causing detrimental techno-socio-economic impacts. Although the corrosion process has been the subject of several studies, factors influencing this process remain a source of contention due to the complexity of the process and its influence by the surrounding environment. Considering the prior reviews, this comprehensive review is considered an early attempt to thoroughly cover the most influential corrosion factors in water pipelines. Corrosion factors have been classified into three main categories: 1) environmental factors; soil factors, external factors, and stray current factors; 2) pipe-related factors, and 3) operational factors. A fault tree analysis diagram was used to map, discuss, and analyze all significant corrosion causes of the buried water pipelines to facilitate easy visualization from basic factors to their intermediate and parent factors. Furthermore, the techno-socio-economic impacts of corrosion on water pipelines and beyond are appropriately addressed to demonstrate the issue’s multi-dimensional importance. The research is expanded to rank these factors using the fuzzy analytical hierarchy process to provide a better understanding of the currently focused research investigation and to enable the extraction of gaps and existing limitations in scholarly literature. The findings revealed that water quality is the most investigated factor, followed by electrical infrastructure and soil quality. Conversely, operational factors exhibit the greatest relative weight (0.428), followed by environmental factors (0.337). These findings highlight areas where further research is needed, and the article proposes potential directions for future studies to address these gaps.
... Besides, no chloride penetration was evident for a period of up to 147 days due to dense microstructure of UHPC. However, the accelerated corrosion techniques are widely studied for rapid prediction and simulation of normal corrosion [44,[46][47][48][49][50][51][52][53]. Several studies reported that the problems of corrosion can be mitigated by utilizing the nano materials, such as nano silica [54], nano titanium [55], nano Graphene-manganese oxide [56], nano metaclay [57], nano blast furnace slag [58], nano graphene oxide [59], nano granite waste [60], solid nano ferrite [61] and other nano materials particles [62][63][64][65]. ...
This research investigates the effect of using nano agriculture waste as a partial substitute to solve increased climatic concerns in addition to producing modern ultra-high-performance fiber reinforced self-compacting concrete (UHPFC-SCC). Three types of nano materials have been incorporated, namely nano sugar cane bagasse ash (NSCBA), nano cotton stalk ash (NCSA), and nano rice straw ash (NRSA) with dosages of 1%, 2%, and 3%, respectively. Fresh concrete properties have been investigated via flow and V-funnel tests while compressive strength was evaluated up to 90 days. X-ray diffraction (XRD) analysis, Raman spectroscopy analysis and scanning electron microscopy (SEM) alongside energy dispersive spectroscopy (EDS) was performed to compliment the strength data. Finally, electrochemical measurements including linear polarization (LPR), open circuit potential (OCP) and impedance spectroscopy were investigated at normal and accelerated corrosion conditions on HSS (high strength steel Gr 60). Results demonstrate that compressive strength improved in the range of 18%− 21% between 28 and 90 days using 3% NSCBA, 3% NRSA or 1% NCSA. This is attributed to the facts that optimum dosage of nano wastes results in densification of the UHPFC-SCC matrix and strength magnitude depended on intertwining of high Ca/Si molar content in the range of 3.14–7.1 compared to 0.52 observed in the control mix (EDS analysis). Further, electrochemical measurements revealed that nano materials improved the charge transfer resistance and bulk resistance of HSS interface as well as retarded the flow of electrons between anode and cathode sites consequently limited the propagation of corrosion.
... In addition, it is quite clear that carbide morphology can influence ductility, and also that carbides can influence the chemical stability of the matrix through the removal of reacting elements. The three main types of carbides found in nickel-based alloy are MC, M 23 C 6 and M 6 C. Cr 7 C 3 can also be present but is rare [14].Since M 6 C carbides are stable at higher temperatures than M 23 C 6 carbides, M 6 C is more beneficial as a grain boundary precipitate to control grain size in the wrought alloy [14].The microstructure of weld metal structure has no major changes after 50 hr aging the zone of retained austenite increased with increasing aging time, this in agreement with R. Anand et al [15], it is clear as that as the aging time increasethe grain size of the Ni part increase, Nickel base exhibit a complex precipitation behavior at elevated temperatures, during welding, furthermore, the precipitation behavior will depend upon the nickel content and the final temperature [16]. Microhardness testing machine was used to measure at least five -hardness values on the weld deposit specimens in the as weld and after agingconditions [12]. ...
Dissimilar metal welding is frequently used to join carbon steels to other materials such as nickel metal. This approach is most often used where a transition in mechanical properties and/or performance in service are required. The power generation industry uses dissimilar metal welding extensively to reduce material costs and enhance performance in elevated-temperature applications.Anodic polarization curves for deposited as weldcondition of Ni weld metal on carbon steel in 3.5% NaCl solution having neutral pH are studying. Anodic polarization curve for thermal aging of Ni weld metal for different agingtimes50,500 and 1000 hr at 550ºCare also recorded. The results indicated that the corrosion current of the Ni weld metal on carbon steel increases as aging time increase,also the grain size of the deposited Nickel increase during thermal aging for different times 50, 500 and 1000 hours respectively
... In addition, it is quite clear that carbide morphology can influence ductility, and also that carbides can influence the chemical stability of the matrix through the removal of reacting elements. The three main types of carbides found in nickel-based alloy are MC, M 23 C 6 and M 6 C. Cr 7 C 3 can also be present but is rare [14].Since M 6 C carbides are stable at higher temperatures than M 23 C 6 carbides, M 6 C is more beneficial as a grain boundary precipitate to control grain size in the wrought alloy [14].The microstructure of weld metal structure has no major changes after 50 hr aging the zone of retained austenite increased with increasing aging time, this in agreement with R. Anand et al [15], it is clear as that as the aging time increasethe grain size of the Ni part increase, Nickel base exhibit a complex precipitation behavior at elevated temperatures, during welding, furthermore, the precipitation behavior will depend upon the nickel content and the final temperature [16]. Microhardness testing machine was used to measure at least five -hardness values on the weld deposit specimens in the as weld and after agingconditions [12]. ...
... This fact justifies the need to both distinguish between different types of chemical entities by microscopic analysis and also to predict the behavior of heterogeneous material structures on a macroscopic scale [21]. One example is the phenomenon of the sensitization of austenitic stainless steel to intergranular corrosion [40], due to segregation of alloy elements and the formation of intermetallic compounds followed by local depletion of the mat erial component providing steel passivity. Xie's work [36] showed an atomic structure analysis of carbides produced by the abovementioned process. ...
The atomic force microscope (AFM) was invented in 1986 as an alternative to the scanning tunnelling microscope, which cannot be used in studies of non-conductive materials. Today the AFM is a powerful, versatile and fundamental tool for visualizing and studying the morphology of material surfaces. Moreover, additional information for some materials can be recovered by analysing the AFM's higher cantilever modes when the cantilever motion is inharmonic and generates frequency components above the excitation frequency, usually close to the resonance frequency of the lowest oscillation mode. This method has been applied and developed to monitor corrosion processes. The higher-harmonic imaging is especially helpful for sharpening boundaries between objects in heterogeneous samples, which can be used to identify variations in steel structures (e.g. corrosion products, steel heterogeneity). The corrosion products have different chemical structures because they are composed of chemicals other than the original metal base (mainly iron oxides). Thus, their physicochemical properties are different from the primary basis. These structures have edges at which higher harmonics should be more intense because of stronger interference between the tip and the specimen structure there. This means that the AFM's higher-harmonic imaging is an excellent tool for monitoring surficial effects of the corrosion process.
... The main cause of its premature replacement is cavitational erosion damage, or worse, by corrosion [3]. Stainless steels with high content in Cr, but having also Ni have a predominantly martensitic structure and are known to have a very good cavitational erosion resistance being used on a large scale for the manufacture of hydraulic turbines [4]. The performances of these steels were very good depending on the particular conditions of the equipment [5,6]. ...
The paper presents the investigations made on samples taken from the related rotor blade of an hospital cooling equipment.The failure analysis was made in order to find if the failure appear because the metallic material used or was functional problem.The objectives of our analysis and techniques used are described below:determining the chemical composition by optical emission spectrometry;determining the hardness of the material;metallographic analysis by optical microscopy;micro compositional and microstructural analysis by scanning electron microscopy (SEM) and by microanalysis, energy dispersive X-ray (EDAX). Research has highlighted the quality of piece elaboration and casting, which led to a long life of its use.
In this study, the influence of laser surface cleaning (LSC) on the wear and corrosion behaviors of 304L stainless steel (SS304L) is discussed. A kilowatt-level (1140 W) Nd:YAG laser with different hatch distances and repetition times is applied to remove the corrosion layer of SS304L, and its corresponding effects on SS304L are examined. Electron backscatter diffraction (EBSD) and kernel average misorientation (KAM) analyses of LSC-induced microstructural modifications reveal a smaller grain size and larger strain rate after the LSC process. In addition, an electron probe X-ray microanalyzer (EPMA) confirms the remaining local Cr-depletion regions even after a complete corrosion layer removal. These Cr-depletion regions are developed during the corrosion process, and an additional LSC process significantly reduces the Cr-depletion regions. Electrochemical tests are conducted to examine the corrosion behavior of the base metal and LSC specimens, and a larger corrosion resistance is achieved with fewer local depletion regions. Moreover, tribological tests reveal that a higher wear resistance is achieved after the LSC process owing to an increase in the surface microhardness.
The corrosion behavior of austenitic stainless steel was investigated under both static and dynamic conditions. In this study, corrosion behavior of welded and unwelded austenitic stainless steels, SS304, SS310, SS316 were investigated using three different stirring speeds; 100, 200, 350 rpm and were subjected to two different corrosive
environments; seawater (3.5% NaCl), and acidic ferric chloride (FeClᴣ). The rate of corrosion was measured using spectrophotometry. The microstructure was examined using optical microscopy. Experimental results indicated that the highest corrosion rate was observed in acidic ferric chloride, 8.56 mg. min-1.cm-2 for SS304 at 350 rpm speed (high mechanical stress condition), compared to seawater under the same conditions, 7.96×10-4 mg. min-1.cm-2. Welded stainless steel area were highly sensitive to the corrosive environment as a result of the increasing thermal stresses in both the weld zone and the heat affected zone (HAZ). Also, the corrosion rate was
found to increase with increasing the stirring speed due to its effect on the mass transfer and mechanical stresses.
The paper describes the problem of steel pipes corrosion in domestic hot water supply systems. A case study of abnormally high rate of corrosion of galvanized steel pipes in a hot water supply system, installed in a complex of residential and public buildings, was considered. The rapid corrosion led to premature failure of these pipelines. Onsite visual inspection, chemical analysis of the tap water with LSI/RSI calculation and scanning electron microscopy and energy-dispersive X-ray spectroscopy analysis were used during this study. The basic factors that lead to pitting corrosion were established: quality of source water (its high corrosion activity), high temperature and local increase in oxygen content near the pipe surface. A possibility of microbial corrosion was also assumed.
The corrosion behavior of austenitic steel was investigated under both static and dynamic conditions. In this study, corrosion behavior of welded and unwelded austenitic stainless steels, SS304,SS310,SS316 were investigated using three different stirring speeds,100,200,350 rpm and were subjected to two different corrosive environments; seawater (3.5%NaCl) and acidic ferric chloride (FeCl3). The rate of corrosion was measured using spectrophotometry. The microstructure was examined using optical microscopy. Experimental results indicated that the highest corrosion rate was observed in acidic ferric chloride, 8.56 mg/(min*cm2) for SS304 at 350 rpm speed (high mechanical stress condition), compared to sea water under the same conditions,7.96 x 10-4 mg/(min*cm2). Welded stainless steel area was highly sensitive to the corrosive environment as a result of increasing the thermal stresses in both the weld zone and the heat affected zone (HAZ). Also, the corrosion rate was found to increase with increasing the stirring speed due to its effect on the mass transfer and mechanical and thermal stresses.
The degradation of carbon mild steel under cavitation erosion-corrosion exposure was studied by means of a 20 kHz ultrasonic device with a piezoelectric inducer. Possibilities of estimation of material failure by current measurement techniques are presented and discussed. The effect of cavitation exposure of the mild steel has been investigated in situ with the dynamic electrochemical impedance spectroscopy technique. Estimation of the surface degradation rate is enabled by an adequate equivalent circuit selection. A dynamic impedance method was used to verify the impedance parameters online during the measurement. These measurements are assisted by estimation of the weight loss function commonly used for the evaluation of erosion-corrosion resistance of materials. (C) 2008 The Electrochemical Society.
In the weldments of 2.25Cr-1Mo and 9Cr-1Mo ferritic steels, the regions with different microstructures were identified as weld metal, heat-affected zone (HAZ) and base metal. When exposed to high temperatures, the HAZ of 2.25Cr-1Mo steel and the weld crown region of 9Cr-1Mo steel were found to oxidize at higher rates, and develop much thicker scale than other regions in the weldments of the respective steels. SEM/EDS point analyses and SIMS depth profiles indicate that the scale over the regions showing inferior oxidation resistance are considerably less in free chromium content. The difference in the oxidation behavior of the different regions was found to arise from the difference in the Cr content of the inner layer of the protective oxide. Possible remedial measures to minimize the high oxidation rates in certain regions of the weldments of the two steels are also discussed.
The relative sensitization susceptibilities of autogeneous type 308 (UNS S30800) stainless steel (SS) tungsten inert gas (TIG) welds were investigated by isothermally heat treating welds for various lengths of time at 550 and 600°C and testing for intergranular corrosion resistance in ASTM A262E. The welds possessed three different microstructures: cellular (single-phase) austenite, duplex with skeletal ferrite, and duplex with lath ferrite. As expected, the fully austenitic welds were highly susceptible to sensitization. In contrast, welds with skeletal ferrite exhibited only limited susceptibility to sensitization. Heat treatments at 600°C for longer than 1 h and at 550°C longer than 48 h did not sensitize welds with skeletal ferrite. Duplex welds with lath ferrite exhibited strong resistance to sensitization. However, because of the greater amount of interfacial austenite-ferrite boundary area present in the lath ferrite welds, theoretical analysis predicted their immunity to sensitization. The discrepancy between theory and experiment appears to result from the former not accounting for the dependency of carbide precipitation at two-phase boundaries on the relative orientations of the austenite and ferrite grains. Because of the latter consideration, the effective amount of austenite-ferrite boundary area in welds with lath ferrite is less than the actual amount.
Highlights
► We document a failure analysis on weld decay in stainless steel due to sensitisation. ► It is less likely that hydrogen affected the failure. ► The electropolishing process could not cause hydrogen embrittlement. ► Recommend introducing coincidence site lattice boundaries for preventing the failure.
A model is developed to predict the chemistry, corrosion potential and rate of pipeline steels in a crevice formed when a coating disbonds from a pipe surface. The gap of the coating disbonded region is assumed to vary with distance from the mouth. The effect of this gap variation on the chemistry and corrosion rate in the coating disbonded region is investigated in this study through modeling. The preliminary model results suggest that overall, the variation of the disbondment gap with distance has an insignificant effect on the pH, corrosion potential and rate in the coating disbonded region. Unlike some conventional crevice corrosion often associated with a large cathode-to-anode area ratio, the area ratio here is rather relatively small and the pH commonly falls in the neutral or alkaline range. Within this pH range, even if the pH varies within a few units across the crevice length, the variation of the crevice corrosion rate is not significant. This paper reports on and discusses the fundamental principles used for the model, some key model results, and the practical implications of the results.
Sherritt International Corporation experienced corrosion failures with the 316L stainless steel tubing in a high-pressure still condenser employed for ammonia recovery. A detailed failure analysis was conducted on the condenser tubing to determine the mode and the root cause of the failure. The analysis included both optical and scanning electron microscopy (SEM) of the inner and outer surfaces of the tube as well as characterization of the corrosion products using energy-dispersive X-ray spectroscopy (EDX). Results revealed that the corrosion attack was confined to the first ∼100mm of the tubing at the inlet where the tube was connected to the top tubesheet. The tube suffered both external stress-corrosion cracking (SCC) and crevice corrosion from the shell side (water side), and wall thinning of the inner surface (the tube side) due to erosion corrosion. It was evident that failure of one of the tubes occurred due to SCC that penetrated the whole wall thickness and resulted in a leak failure. Some prevention measures are proposed to avoid this type of corrosion attack in the future.
The effect of strain rate (SR) on the non-stationary electrochemical process of the passive layer cracking, for SRs covering a range of values (10−5 to 16×10−5 s−1) was examined. Investigations were conducted on 304L stainless steel at room temperature in chloride solutions using dynamic electrochemical impedance spectroscopy. As a result, a set of instantaneous impedance spectra reflecting the system dynamics was recorded and is presented in this paper. Moreover, changes of electrochemical parameters and their derivatives are included in the paper for a better description of the substantial dynamics.
The concept of a critical potential below which pitting of 18–8 and other passive alloys does not occur in aqueous Cl− media is affirmed. Increasing Cl− concentration shifts the critical potential to more active values. The potential is shifted to more noble values by presence
of other anions, e.g.,
,
,
,
, sufficient concentrations of which act as pitting inhibitors. Lowering of temperature similarly enobles the critical potential.
The shift at 0°C exceeds the oxidation‐reduction potential for
accounting for resistance of 18–8 to pitting in
solutions at ice temperature but not at room temperature. The critical potential is not affected appreciably in the acid
pH range; it moves markedly in the noble direction in the alkaline range corresponding to observed resistance to pitting in
alkaline Cl− media. These results are interpreted in terms of competitive adsorption of Cl− and other anions for sites on the alloy surface. Only at a sufficiently high surface concentration of Cl− is oxygen, making up the passive film, displaced locally, and passivity thereby destroyed resulting in a pit. The special
behavior of
inhibition and factors affecting reproducibility of measurements are discussed.
A novel dynamic electrochemical impedance spectroscopy (DEIS) technique has been developed that offers the possibility to determine impedance characteristics in a time domain during the rupture of the protective passive layer. This ability is associated with the analysis methodologyof the technique, which enables selective time–frequency analysis of the measurement data. This paper proposes that the DEIS technique allows the acquisition of instantaneous changes during the passive layer cracking process, which is strongly related to the initiation stage of stresscorrosion cracking. Moreover, the principles of application of the novel method in such investigations are discussed.
The cavitation erosion and corrosion characteristics of various engineering alloys including grey cast iron, steels, copper-based alloys and stainless steels were studied by means of a 20 kHz ultrasonic vibrator at a peak-to-peak amplitude of 30 μm in distilled water and in 3.5% NaCl solution at 23°C. The contributions of pure mechanical erosion, electrochemical corrosion, and the synergism between erosion and corrosion to the overall cavitation erosion–corrosion in 3.5% NaCl solution were determined. It was found that in 3.5% NaCl solution, the effect of corrosion on the overall cavitation erosion–corrosion was most pronounced in mild steel and grey cast iron, and negligible in stainless steels. The stainless steels only suffered pure mechanical erosion in 3.5% NaCl solution in the presence of cavitation owing to the unfavourable local environment for pit growth.
Heat exchanger tubes were locally heavily damaged by desalted crude forming a shell side stream under the pressure of 2.6 MPa and at the temperature of 385-395 K. Boiler steel tube temperature was 97 K higher compared to that of the crude oil at its inlet to the exchanger. Two types of segmental baffles effected cross vortex type flow that was lowered nearly to a standstill at locations where the highest damage occurred. Close to the baffles where the damage was the highest the flow was completely different from that of the window flow. These were found from analyses of the flow and of locations of perforations. Most of the tube surface was with no damage and was covered with protective organic-inorganic deposit. Electrochemical investigation proved a cathodic character of the deposited film against bare steel. Metallography examination of the steel showed typical structures that could not affect much the damage. The crude with low water content was not found aggressive when a corrosion test was performed at elevated temperature. The tests excluded the possibility for high rate of electrochemical corrosion at the surfaces with removed protective layers. The only reason of the damage may be cavitation corrosion at the ways of crude slow vortex flow at which temperature was high enough to allow explosions of low volatile components [1].
The production of passivity is considered as the anodic process of oxide-film formation, initially as a monolayer, from the thermodynamic and kinetic points of view. The influence of readily adsorbable anions such as Cl- in hindering passivation and in promoting breakdown of passivity is treated in terms of the relative adsorption of anions and water at the metalsolution and oxide/solution interfaces, as influenced by anion concentration and electrode potential. A new "mechanical" mechanism for breakdown is proposed. It is shown that for metal/electrolyte-solution systems, the occurrence at an anode of (i) crystallographic etching (ii) crystallographic pitting (iii) passivity (iv) hemispherical "bright" pitting (v) anodic brightening (vi) "imperfect" brightening can be produced by suitable variation of potential and anion/water concentration ratio. A new type of "potential/[anion]/[water]" diagram is proposed for the display of experimental data on such systems.
This paper presents an example of grain boundary engineering (GBE) for improving intergranular-corrosion and weld-decay resistance of austenitic stainless steel. Transmission and scanning electron microscope (TEM and SEM) observations demonstrated that coincidence site lattice (CSL) boundaries possess strong resistance to intergranular precipitation and corrosion in weld decay region of a type 304 austenitic stainless steel weldment. A thermomechanical treatment for GBE was tried for improvement of intergranular corrosion resistance of the 304 austenitic stainless steel. The grain boundary character distribution (GBCD) was examined by orientation imaging microscopy (OIM). The sensitivity to intergranular corrosion was reduced by the thermomechanical treatment and indicated a minimum at a small roll-reduction. The frequency of CSL boundaries indicated a maximum at the small roll-reduction. The corrosion rate was much smaller in the thermomechanical-treated specimen than in the base material for long time sensitization. The optimum thermomechanical treatment introduced a high frequency of CSL boundaries and the clear discontinuity of corrosive random boundary network in the material, and resulted in the high intergranular corrosion resistance arresting the propagation of intergranular corrosion from the surface. The optimized 304 stainless steel showed an excellent resistance to weld decay during arc welding.
This paper investigates the solid particle erosion–corrosion performance of an experimental high velocity oxy-fuel (HVOF) sprayed nickel–aluminium bronze (NAB) coating using conventional gravimetric techniques as well as in situ electrochemical analysis. The coating consists of HVOF powders from three alloys: stainless steel alloy, nickel-based alloy and aluminium bronze alloy. It is a candidate coating for marine applications as a cost effective replacement of existing castings and to improve component life. The coating was subjected to pure erosion, flow corrosion and erosion–corrosion tests. A jet impingement slurry erosion rig was used to carry out the experiments; the effects of jet velocity were investigated. By gravimetric analysis the degree of synergy was evaluated and a constant was revealed which described to what extent the presence of corrosion products/films reduces the erosivity and promotes negative synergy. Likewise, standard deviations of electrochemical current measurements are shown to reveal the presence of protective film formation under flow corrosion and film breakdown under erosion–corrosion conditions. Separation of the erosion-enhanced corrosion component revealed that at high erodent kinetic energies, erosion-enhanced corrosion dominates and generates a positive synergy. At lower energies, this coating system forms a protective film which reduces the contact conditions on impingement and a negative synergy results. Overall, correlations between the mass loss and electrochemical measurements have been established and were used to identify and quantify synergy.
Microbiologically influenced corrosion of carbon steel has been investigated. Carbon steel coupons were exposed online in the cooling water system of a nuclear test reactor to assess the microbial growth on the coupons and the corrosion phenomena. Iron bacteria, sulphate reducing bacteria (SRB) and culturable aerobic heterotrophic bacteria (CAHB) were monitored both on the coupons and in the cooling water. Corrosion rate was assayed by weight loss method and corrosion products analysed by XRD and Mossbauer spectroscopy. Extensive tuberculation of carbon steel coupons was noticed. SEM pictures revealed the presence of ensheathed filamentous iron bacteria encrusted with corrosion products. Beneath the tubercles significant pitting and SRB induced corrosion in the form of concentric rings was observed. From the phase analysis, the following compounds were found to be present: γ-Fe2O3, Fe2PO5, FePS3, Fe(PO3)3 and BaFeO3 − x. From the present study it is inferred that iron bacteria (Leptothrix sp.) and SRB (Desulfovibrio sp.) are responsible for the corrosion of carbon steel. The role of these bacteria in influencing the corrosion of carbon steel is highlighted.
Corrosion of iron presents a serious economic problem. Whereas aerobic corrosion is a chemical process, anaerobic corrosion is frequently linked to the activity of sulphate-reducing bacteria (SRB). SRB are supposed to act upon iron primarily by produced hydrogen sulphide as a corrosive agent and by consumption of 'cathodic hydrogen' formed on iron in contact with water. Among SRB, Desulfovibrio species--with their capacity to consume hydrogen effectively--are conventionally regarded as the main culprits of anaerobic corrosion; however, the underlying mechanisms are complex and insufficiently understood. Here we describe novel marine, corrosive types of SRB obtained via an isolation approach with metallic iron as the only electron donor. In particular, a Desulfobacterium-like isolate reduced sulphate with metallic iron much faster than conventional hydrogen-scavenging Desulfovibrio species, suggesting that the novel surface-attached cell type obtained electrons from metallic iron in a more direct manner than via free hydrogen. Similarly, a newly isolated Methanobacterium-like archaeon produced methane with iron faster than do known hydrogen-using methanogens, again suggesting a more direct access to electrons from iron than via hydrogen consumption.
The impact of road salt on a wellfield in a complex glacial moraine aquifer system is studied by numerical simulation. The moraine underlies an extensive urban and industrial landscape, which draws its water supply from >20 wellfields, several of which are approaching or have exceeded the drinking water limit for chloride. The study investigates the mechanisms of road salt infiltration, storage, and transport in the subsurface and assesses the effectiveness of mitigation measures designed to reduce the impact. The three-dimensional transport model accounts for increases in salt loading, as well as growth of the urbanized area and road network over the past 50 years. The simulations, which focus on one impacted wellfield, show chloride plumes originating mainly at arterial roads and migrating through aquitard windows into the water supply aquifers. The results suggest that the aquifer system contains a large and heterogeneously distributed mass of chloride and that concentrations in the aquifer can be substantially higher than the concentrations in the well water. Future impact scenarios indicate that although the system responds rapidly to reductions in salt loading, the residual chloride mass may take decades to flush out, even if road salting were discontinued. The implications with respect to urban wellfields in typical snow-belt areas are discussed.
Weld decay in AISI 304 stainless steel
- T G Gooch
- D C Willingham
Gooch TG, Willingham DC. Weld decay in AISI 304 stainless steel. Met Constr
Brit Weld J 1971;3:366.
A polarisation curve for (—) steel AISI 304 in the area of oxidised passive film, and
- Fig
Fig. 9. A polarisation curve for (—) steel AISI 304 in the area of oxidised passive film, and (---) within the area of the parent material.
Corrosion of weldments. ASM handbook: welding, brazing, and soldering
- A Wahid
- Olson Dl
- Matlo
- Dk
Wahid A, Olson DL, Matlo DK. Corrosion of weldments. ASM handbook: welding, brazing, and soldering, vol. 6. ASM, International; 1993.
Properties of a fully austenitic stainless steel weld metal for severe corrosion environments
- A Backman
- B Lundqvist
Backman A, Lundqvist B. Properties of a fully austenitic stainless steel weld
metal for severe corrosion environments. Weld J 1977;56:23s-8s.