Steel Corrosion Products Research Articles

A Thermodynamic Model for the Prediction of Mild Steel Corrosion Products in an Aqueous Hydrogen Sulfide Environment

In the present study, a comprehensive thermodynamic model, depicted by Pourbaix diagrams, was developed with the relatively narrow focus on corrosion of mild steel in oil and gas field conditions. This thermodynamic model focuses on predicting the formation of metastable or stable corrosion products in sour environments at elevated temperature up to 250°C, which includes mackinawite (FeS), greigite (Fe3S4), the pyrrhotite group (Fe1–xS, x = 0 to 0.17), and pyrite (FeS2). The model is based on theoretical thermodynamic calculations and data found in the open literature. The appearance of Pourbaix diagram is significantly affected by temperature. Long-term corrosion experiments at two different temperature (25°C and 80°C) were conducted to investigate the corrosion product stability predictions made by the Pourbaix diagrams. The equilibrium state predicted in the Pourbaix diagrams was compared with the quasi-equilibrium state attained in the long-term experiments. To this end, the surface pH, bulk pH, ferro...

Thermodynamic and fully-coupled reactive transport models of a steel–bentonite interface

Engineered barrier system (EBS) designs for the geological disposal of high-level radioactive waste often include a bentonite buffer, the primary function of which is to protect metal waste containers or overpacks from mechanical shearing. The buffer also acts as a barrier to solute transport. One potentially deleterious process that may occur in the buffer is the alteration of swelling clay to iron-rich minerals, some of which have a limited capacity to swell. There is a dearth of relevant natural analogues of iron–bentonite interactions, and experimental data do not provide an unequivocal indication of the conditions that will promote non-swelling clay minerals (such as berthierine) to form rather than swelling clays (such as iron-rich saponite). In addition, many of the previously-published reactive transport models of iron–bentonite or iron–claystone interfaces have not considered how evolution of mineral–fluid equilibria in the bentonite buffer could affect the nature and rate of steel corrosion. In this study, new thermodynamic models of iron-rich clay minerals are presented which suggest that the activities of major ions, especially Fe2+, Fe3+, Al3+, H+ and SiO2(aq), act as key controls on the relative stabilities of iron-rich clay minerals. In particular, they suggest that Fe-saponite is stabilised under low fO2(g) conditions when SiO2(aq) activities are buffered by quartz or more soluble silica polymorphs (e.g. chalcedony). Iron-rich 1:1 clay minerals, such as berthierine, tend to be stabilised in fluids that are quartz under-saturated. The thermodynamic models were used to inform the development of three fully-coupled reactive transport models of a steel–bentonite interface: (1) steel corrosion reaction applied on a boundary directly in contact with bentonite at a fixed rate; (2) steel corrosion reaction applied on a boundary directly in contact with bentonite at a diffusion-limited rate; and (3) a ‘corrosion cell’ representation with a fixed steel corrosion rate.The extent and nature of the alteration predicted by the models was found to be sensitive to model conceptualisation. The corrosion cell assumption leads to steel corrosion products including magnetite and siderite and the alteration of primary minerals to berthierine (∼2cm thick layer forming over 100000years, with partial loss of montmorillonite to a depth of ∼9cm). In contrast, the boundary corrosion assumption with a fixed steel corrosion rate leads to quicker alteration to iron-rich clay minerals. If the diffusion-limited corrosion rate assumption is made, the steel corrosion rate varies over time as the bentonite porewater composition evolves, and the spatial extent of alteration is much more limited (millimetre scale). Although much progress has been made, a number of uncertainties associated with modelling bentonite evolution remain, especially with regard to ion transport through smectite interlayers and the potential for complex couplings between chemical and physical processes.

Environmental Conditions for Akaganeite Formation in Marine Atmosphere Mild Steel Corrosion Products and Its Characterization

The corrosion of mild steel in chloride-rich atmospheres is a highly topical issue. The formation of the oxyhydroxide akaganeite (β-FeOOH) in this type of atmosphere leads to a notable acceleration of the steel corrosion process. The scientific literature contains many references to outdoor marine atmospheric tests, but so far has failed to clarify two basic matters in relation to akaganeite: the environmental conditions necessary for its formation, and its morphological characterization. Research has been performed at three atmospheric corrosion stations located at Cabo Vilano wind farm (Camariñas, Spain) at different distances from the shoreline (332, 590, and 2,400 m), with chloride deposition rates of 390, 74, and 29 mg/m2/day, respectively, with the exposure of mild steel specimens for 1 year. This paper reports the environmental conditions that generally led to the formation of akaganeite: an annual average relative humidity of around 80% or higher, and simultaneously, an annual average chloride deposition rate of approximately 60 mg/m2/day or higher. Rigorous characterization of akaganeite was performed by x-ray diffraction, scanning electron microscopy/energy dispersive spectroscopy, and transmission electron microscopy/selected area electron diffraction.

Effects of Nutrition on Mild Steel Corrosion by Sulfate Reducing Bacteria under Aerobic Environment

Sulfate reducing bacteria (SRB) are traditionally considered as anaerobic organism. In this paper, the potential of sulfate reducing bacteria to cause mild steel corrosion under aerobic situation was investigated. Natural biopolymer agar and sulfate reducing bacteria cells were used to produce artificial biofilm. Micro-sensors were used to investigate the microenvironment in artificial biofilm. Environmental scanning electron microscopy and energy dispersive spectroscopy were used to study mild steel corrosion covered by artificial biofilm. The results indicated that SRB could grow and reduce sulfate both in suspension and in biofilm. The hydrogen sulfide produced by SRB and mild steel corrosion were influenced by the nutrients in the environment. The concentration of H2S in SRB biofilm exposed to culture medium was as twenty times as that exposed to marine water. The main corrosion product of mild steel in culture medium was iron sulfide, whereas the main product of mild steel in marine water was iron oxide.

Experimental and Quantum Chemical Studies on the Corrosion Inhibition Potential of Phthalic Acid for Mild Steel in 0.1 M H2SO4

The corrosion inhibition potential of phthalic acid for mild steel in 0.1 M sulphuric acid was studied using experimental (weight loss, gasometric, FTIR and Scanning electron microscopy) and theoretical (semi empirical, Ab initio and DFT) approaches. Results obtained from weight loss measurements indicated that phthalic acid inhibited the corrosion of mild steel and recorded average and instantaneous maximum inhibition efficiencies of 55.48 and 87.34% at 303 K and at a concentration of 0.1 M respectively. Thermodynamic/adsorption considerations revealed that the adsorption of the inhibitor is exothermic, spontaneous and supported the mechanism of physical adsorption. The adsorption behaviour of the inhibitor was best described by the Langmuir adsorption model. FTIR spectra obtained from the corrosion product of mild steel in the absence and presence of the inhibitor revealed the existence of interaction between the inhibitor and the metal surface due to some shifts in the functional groups of the compound after adsorption. Scanning electron micrographs of the corroded metal (in the absence and presence of the inhibitor) revealed that phthalic acid prevented the corrosion of mild steel by forming protective coverage on the surface of the metal. Calculated quantum chemical parameters were found to be in good agreement with those reported for some good corrosion inhibitors. Although results obtained from Ab initio calculations for condensed Fukui functions were slightly at variance with those obtained from DFT calculations, considerations of Huckel charges on the atoms of the molecule, bond length, HOMO and LUMO molecular orbital plots clearly supported DFT results which indicated that the sites for nucleophilic and electrophilic attacks corresponded to atoms O(11) and C(4) respectively.

ラマン分光法を用いた金属材料の腐食生成物のin-situ測定

The corrosion of metallic materials is caused by action of aqueous or gaseous environment and the products of the corrosion greatly depend on the environmental condition. It is desired that the identification of the products is done under the in-situ environmental condition. Raman spectroscopy is one the methods to identify them under the condition. The application of Raman spectroscopy to detection of the corrosion products of steel, zinc, and titanium is introduced.

Key Phenomena Governing HLW Glass Behavior in the French Deep Geological Disposal

ABSTRACTAccording to the Planning Act of 28th June 2006, Andra is in charge of ensuring the sustainable management of all radioactive waste generated in France, especially the high-level and long-lived vitrified waste produced from spent fuel recycling.Since 2006, all the studies and research related to the components of HLW cells have been incorporated into a broader R&D program which aims at characterizing and modeling (i) the glass matrix dissolution, (ii) the corrosion of the overpack and the lining, and (iii) the claystone evolution in the near field, considering all the interactions between these surrounding materials. This program, coordinated by Andra, has involved up to eighteen laboratories.After closure of disposal cells and overpack failure, glass alteration is expected to begin in partially saturated conditions due to hydrogen production resulting from carbon steel corrosion in anoxic conditions. Therefore, the glass should at least partially be hydrated by water vapor during thousands of years until complete saturation. A part of the studies aimed to determine the glass behavior in such conditions, the influence of the main parameters (temperature, relative humidity) and consequences of vapor hydration on subsequent radionuclides release by water leaching.In addition, the major part of the work focused on the influence of the environment on glass alteration. The effect of clay pore water on glass alteration rates (initial rate, rate drop and residual rate) was determined and particularly that of pH and magnesium. The nature of steel corrosion products and their interactions with glass alteration were also investigated. All these studies relied on experiments in surface laboratories, in Andra’s underground laboratory, together with natural or archeological analogs and modeling studies.

Determination of the Levels of Some Metal Ions in the Blood, Liver and Kidney of Wistar-Albino Rat after Surgical Implantation of Stainless Steel Arch Bar

The study was carried out to determine the accumulated levels of the anticipated major corrosion products of stainless steel (SS) arch bar used for maxillomandibular fixation and the affinity of the corrosion products of SS arch bar for some organs, when it is implanted into the mandible of Wistar albino rat (Rattus norvegicus) for six weeks. Ten experimental rats with implantation and ten control rats were each sacrificed at the end of the six weeks by a 1.5 mL lethal dose of chloroform. The concentrations of Co, Cr, Fe, Mn and Ni in the blood and oven-dried kidney and liver of the two groups were determined using atomic absorption spectrophotometry. The highest mean concentration of Fe ions was accumulated in blood (0.5423 ± 0.0150 mg/kg) and least in the liver (0.4675 ± 0.0060 mg/kg). The accumulated levels of Fe ions in the blood of the experimental and control rat (0.3897 ± 0.0703 mg/kg) are statistically different at P < 0.05. The concentration of Ni ions in the experimental rats was statistically elevated compared to the control. The total metal ions accumulated in the blood and kidney followed the ranking Ni > Fe > Co > Mn, this ranking showed a different trend from that accumulated by the liver Fe > Ni > Mn > Co; though the percentage composition of these metals in the arch bar has the ranking Fe > Ni >  Cr > Mn > Co. Ni showed a high affinity for kidney and blood of the rat, while Fe showed affinity for all the organs studied. Ni ions released from SS arch bar was statistically elevated in kidney and Fe ions in blood of the experimental animal model. The study affirms that SS arch wire like other medical implants corrode when bathe by bio-fluids with small amounts of metal ions being accumulated by surrounding organs.

Studies on obtaining of aluminium phosphates modified with ammonium, calcium and molybdenum

Studies on obtaining of aluminium phosphates modified with ammonium, calcium and molybdenum were implemented. Reagent grade substrates (NH4)2HPO4, CaCO3, (NH4)6Mo7O24·4H2O, aqueous ammonia, and amorphous Al(OH)3 were prepared and used in the experiments. An influence of process parameters, i.e. reaction time (60±30min) and total salt concentration (50±10wt%) on the phase composition and product properties was determined. Statistical software STATISTICA 10 for planning and evaluation of the experiments was used. Based on the statistical evaluation of planned research by the plan fractional factorial design at three levels 3(k−p), process parameters allowing to obtain the material of with expected physicochemical properties were determined. The content of aluminium, calcium and molybdenum in the products was determined using ICP-AES technique. The phosphates and ammonium content was determined by means of a spectrophotometric method and ion selective electrode Orion 11–35 type, respectively. The phase composition of the obtained materials was studied using XRD analysis. The specific surface area was calculated using the BET method and the particle size was determined by LSM. The Tafel experiments for an uncoated mild steel (immersed in an aqueous phosphate extract in 3.5wt% NaCl solution) were performed. The steel corrosion products as well as tested phosphates were examined by means of scanning electron microscope with a cold field emission coupled with the energy dispersive X-ray analyzer. The content of the individual components was in the range of 10.52–16.33wt% (Al), 10.59–18.54wt% (Ca), 0.59–5.28wt% (Mo), 0.1–4.91wt% (NH3), and 6.97–23.4wt% (P2O5). The products were characterized by different physicochemical parameters. The surface area was in the range from 6 to 63m2/g and the oil absorption was 36–71g of oil/100g of product, whereas the average particle size of products reached 221–319nm. The Tafel tests revealed markedly higher anticorrosive properties of aluminium phosphates modified with ammonium, calcium, molybdenum in comparison to commercial aluminium phosphate and zinc phosphate.

Investigations of the diverse corrosion products on steel in a hydrogen sulfide environment

The corrosion products of carbon steel in aqueous H2S environment are investigated. The products, which include mackinawite, cubic FeS, troilite, and pyrite, are characterized through their shapes, chemical compositions and crystal structures. Mackinawite appears with a flake shape. Cubic FeS has a perfect/truncated octahedral shape, and pyrite is framboid-shaped. Flower-shaped troilite is developed from beam- or hexagonal wire-shaped grains by electrostatic interactions along a certain lattice plane. The large single beam-shaped troilite has a growth pattern along the c axis. The corresponding crystal structure and micro-morphology of the corrosion products are provided, and the three-dimensional models of them are generated.

Effects of Alternating Current (AC) Frequency on Corrosion Behavior of X80 Pipeline Steel in a Simulated Acid Soil Solution

The effect of frequency of the applied alternating current(AC) on corrosion behavior of X80 steel in an artificial liquid aiming to simulate the acid soil medium of Yingtan area was studied by means of electrochemical measurement, immersion test and surface characterization technique.The results showed that with the increasing AC frequency, the corrosion rate and the corrosion degree of X80 steel decreased gradually. The corrosion product of X80 steel under the applied AC was loose with many cracks thus could not offer proper protection to the substrate. The offset of corrosion potential of X80 steel decreased as the AC frequency increases. With the increase of AC frequency, the oscillation amplitude of anode and cathode polarization curve gradually receded. In the range of the test frequency, the applied AC to X80 steel not only induced the increase of the current density for both anode and cathode, but also the change of cathode reaction from mixing control to activation control.

Study on Corrosion Behavior of A3 Carbon Steel in the Manicipal Sludge

Taking the corrosion depth as the evaluation index, the influence law of different factors such as pH and moisture content of sludge, corrosion temperate on metal corrosion behavior was studied by single factor experiment. The corrosion product was characterized by SEM and EDX at last. The results show that the corrosion depth of A3 carbon steel increases with the increase of temperature, moisture content and acidity of sludge. The corrosion product of A3 carbon steel is mainly brown loose substance, the corrosion extent of carbon steel is deep and many elements are soaked into carbon steel. Metal corrosion results from different temperatures and different pH of sludge is non-uniform, while metal corrosion results from different moisture content of sludge is uniform.

Migration behavior of plutonium affected by ferrous ion in compacted bentonite by using electrochemical technique

ABSTRACTThe migration behavior of plutonium is expected to be affected by the corrosion products of carbon steel in compacted bentonite at high-level waste repositories. Electrochemical experiments were carried out to simulate the reducing environment created by ferrous iron ions in equilibrium with anoxic corrosion products of iron. The concentration profiles of plutonium could be described by the convection -dispersion equation to obtain two migration parameters: apparent migration velocity Va and apparent dispersion coefficient Da. The apparent migration velocity was evaluated within 1 nm/s and was found to be independent of the experiment duration and the dry density of bentonite in the interval 0.8-1.4 Mg/m3. The apparent dispersion coefficient increased with the experiment duration at a dry density of 1.4 Mg/m3. The results for other dry densities also showed the same trend. These findings indicate that plutonium migration likely starts after ferrous ions reach the plutonium, in other words, the reducing environment due to ferrous ions could change the chemical form of plutonium and/or the characteristics of compacted bentonite. The apparent diffusion coefficient was estimated to be around 0.5 to 2.2 µm2/s and increased with decreasing the dry density of bentonite.

A Study of the Corrosion Kinetics by Coulometric Detection of Corrosion Products on a Glass Carbon Electrode

The paper reports the theoretical and experimental bases of the CDCP (Coulometric detection of corrosion products) method and examples of its application for the quantitative determination of the ionic forms of corrosion products of carbon steel, including the heat-affected corrosion areas of welding seams under strain ageing (ACWS). The experiment technique that we developed allowed us to perform selective determination of corrosion products (e.g., Fe +2 and Fe +3 in a single experiment) in the range of 1–5 μg with standard deviation s r = 0.05.

Behavior of two eco-compatible duplex systems used in the construction industry against corrosion

Two types of coated steels are currently competing in the construction industry: the hot-dip galvanized steel (HDGS) and the 55%Al–Zn alloy coated steel (HDZAS). Both systems are typically coated by a chromate-based conversion film, which is dangerous for human health and environment. Furthermore, for aesthetics purposes and/or to prolong their expected or planned service life, they are painted designing each paint system as a function of the service conditions to which they will be subject to. The present work reports on a comparative study of two duplex systems: steel/metal coating/organic coating. In both cases, the chromate-based pretreatment was replaced by another one that features γ-mercaptopropyltrimethoxysilane (MTMO) as an active element. The organic coating used was a water-based polyurethane. Behavior of this paint against corrosion was assessed by exposing the samples in salt spray or humidity chambers, and monitoring its evolution by electrochemical impedance spectroscopy, visual observation, scanning electron microscopy and energy dispersive X-ray analysis. The results revealed that: MTMO was suitable for promoting adhesion both in HDGS and HDZAS; in humidity chamber, both duplex systems provided good protection; the presence of corrosion products of the base steel and paint blistering was detected in the HDGS/paint system seventy-two days after exposure; however, 150 days after that, none of these effects were observed in the HDZAS/paint system; differences in behavior were significant in Salt spray chamber: speed of paint delamination from the mark done and the bulk of corrosion products generated was much higher in HDGS/paint system than in HDZAS/paint.

Anaerobic Corrosion of Reinforcement

Anaerobic corrosion of steel reinforcement is rarely reported and limited literature is available on the subject. Corrosion of steel is an electrochemical process requiring a supply of oxygen in the presence of moisture. Steel corrosion product usually occupies a much larger volume than the un-corroded steel resulting in cracked or spalled concrete. If the supply of oxygen is restricted, black rust may be formed by the process of anaerobic corrosion. Black rust is not expansive, which makes it particularly difficult to detect in reinforced concrete. This paper presents a case study of anaerobic corrosion in the Mizen Bridge, together with an in-depth review of anaerobic corrosion of reinforcement in concrete, outlining black rust formation, characteristics and detection methods.

Influence of temperature on corrosion rate and porosity of corrosion products of carbon steel in anoxic bentonite environment

The study focuses on the porosity of layers of corrosion products and its impact on corrosion rate of carbon steel in moist bentonite. Measurements were performed in an aggressive Czech type of bentonite – Rokle B75 at temperatures of 90 and 40°C. Aggressiveness of B75 bentonite consists in low content of chlorides. Presence of chlorides in pore solution allows formation of more protective magnetite. The evaluation was made by electrochemical techniques (red/ox potential, open circuit potential, linear polarization resistance, impedance spectroscopy) and resistometric sensor measurements. The result imply that the higher the temperature the more compact is the layer of corrosion products that slightly decelerates corrosion rate compared to the state at 40°C. The state of corrosion products at both temperatures is reversible.

Development and Performance of MnFeCrO4‐Based Electrodes for Solid Oxide Fuel Cells

AbstractImportant advances have been made in SOFC development utilizing a ceramic framework based upon yttria zirconia (YSZ) electrolytes supported upon porous YSZ electrode skeletons. This ceramic framework is sintered at high temperatures with subsequent impregnation and low temperature processing of the active electrode materials. Here we seek to develop this impregnated electrode concept by investigating a novel scaffold material similar to the main corrosion product of ferritic stainless steel. The chromium rich spinel (MnFeCrO4) was used as an electrode support material, either alone or impregnated with (La0.75Sr0.25)0.97Cr0.5Mn0.5O3‐δ, La0.8Sr0.2FeO3‐δ, Ce0.9Gd0.1O2‐δ, CeO2 and/or Pd. In these initial studies it was found that all of the impregnated phases adhere very well to the spinel and considerably enhance performance and stability to a level sufficient for SOFC applications.

Influence of moisture on corrosion behaviour of steel ground rods in mildly desertified soil

PurposeThe purpose of this paper is to study the influence of moisture on corrosion behaviour of steel ground rods in mildly desertified soil and the mechanism behind it.Design/methodology/approachThe specimens were used for weight loss corrosion experiments and polarization scans were taken at different moisture levels. Specimen surfaces were characterized using a scanning electron microscope, energy dispersive spectrometer, and using X‐ray diffraction.FindingsThe results indicated that the moisture content of the soil influenced steel corrosion considerably. The maximum corrosion of 20G and Q235 galvanised steels occurred at 10 per cent and 12.5 per cent soil moisture, respectively. The corrosion products of 20G steel were mostly Fe2O3 and Fe3O4, whereas that of Q235 galvanised steel was Zn5(OH)8Cl2 · H2O.Originality/valueThe paper provides information regarding the relationship between moisture and corrosion of steel ground rods, which is useful for understanding the mechanism of soil corrosion. The research results can provide theoretical guidelines for preventing the corrosion of steel ground rods buried in mildly desertified soil.

Corrosion of Austenitic Steels and Their Components in Vanadium-Containing Chloride Melts

Corrosion behavior of stainless steel types AISI 316L, 316Ti and 321 and their components (iron, chromium, nickel and molybdenum) was studied at 750 0C in NaCl-KCl-VCl2 melts. It was found that iron, chromium and manganese species constitute the major corrosion products of austenitic steels and Fe2+, Cr2+, Ni2+, and Mo3+ ions are formed as a result of interaction of corresponded metal and vanadium-containing chloride melts. It was found that austenitic stainless steels are subjected to high temperature sensitization and this phenomenon determines the intergranular character of steel corrosion. Presence of vanadium ions in electrolyte leads to intensification of corrosion processes due to increased oxidation of electronegative steel components and alloy formation. Metallic molybdenum has highest corrosion resistance among studied construction materials.