Steel Corrosion Products Research Articles

Distribution of millscale on corroded steel bars and penetration of steel corrosion products in concrete

This study investigated a reinforced concrete specimen that had deteriorated in an artificial environment for 2years. The steel/concrete interface and corrosion-induced cracks were observed by SEM to investigate the millscale on the rebar surface and the distribution of rust. The millscale was not further oxidised before the surface cracking of the concrete cover. The penetration of corrosion products into concrete and the formation of a corrosion layer proceeded simultaneously. The rust did not fill the corrosion-induced cracks in concrete. Instead of the three-stage model, a two-stage model is proposed to describe the concrete cracking process induced by steel corrosion.

A Model for the Influence of Steel Corrosion Products on Nuclear Fuel Corrosion under Permanent Disposal Conditions

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A model for the influence of steel corrosion products on nuclear fuel corrosion under permanent disposal conditions

A model was developed to determine the influence of steel corrosion products on α-radiolytic corrosion of spent nuclear fuel inside a failed waste container. The model takes into account the α-radiolysis of water, the reaction of radiolytic H2O2 with UO2 both directly and via galvanic coupling with noble metal particles, the reaction with H2 via galvanic coupling, and the Fenton reaction. The dominant redox control agent was found to be H2, and the critical H2 concentrations required to completely suppress fuel corrosion were calculated. The ability of Fe2+ to scavenge H2O2 had only a minor influence on fuel corrosion processes.

Green Rust Formation during Fe(II) Oxidation by the Nitrate-Reducing Acidovorax sp. Strain BoFeN1

Green rust (GR) as highly reactive iron mineral potentially plays a key role for the fate of (in)organic contaminants, such as chromium or arsenic, and nitroaromatic compounds functioning both as sorbent and reductant. GR forms as corrosion product of steel but is also naturally present in hydromorphic soils and sediments forming as metastable intermediate during microbial Fe(III) reduction. Although already suggested to form during microbial Fe(II) oxidation, clear evidence for GR formation during microbial Fe(II) oxidation was lacking. In the present study, powder XRD, synchrotron-based XAS, Mössbauer spectroscopy, and TEM demonstrated unambiguously the formation of GR as an intermediate product during Fe(II) oxidation by the nitrate-reducing Fe(II)-oxidizer Acidovorax sp. strain BoFeN1. The spatial distribution and Fe redox-state of the precipitates associated with the cells were visualized by STXM. It showed the presence of extracellular Fe(III), which can be explained by Fe(III) export from the cells or extracellular Fe(II) oxidation by an oxidant diffusing from the cells. Moreover, GR can be oxidized by nitrate/nitrite and is known as a catalyst for oxidation of dissolved Fe(II) by nitrite/nitrate and may thus contribute to the production of extracellular Fe(III). As a result, strain BoFeN1 may contribute to Fe(II) oxidation and nitrate reduction both by an direct enzymatic pathway and an indirect GR-mediated process.

Electrochemical and analytical characterization of three corrosion inhibitors of steel in simulated concrete pore solutions

Corrosion inhibitors for steel, such as sodium phosphate (Na3PO4), sodium nitrite (NaNO2), and benzotriazole (BTA), in simulated concrete pore solutions (saturated Ca(OH)2) were investigated. Corrosion behaviors of steel in different solutions were studied by means of corrosion potential (Ecorr), linear polarization resistance (LPR), electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (PDP). A field emission scanning electron microscope (FESEM) equipped with energy dispersive X-ray analysis (EDXA) was used for observing the microstructures and morphology of corrosion products of steel. The results indicate that, compared with the commonly used nitrite-based inhibitors, Na3PO4 is not a good inhibitor, while BTA may be a potentially effective inhibitor to prevent steel from corrosion in simulated concrete pore solutions.

Analysis of Short-Term Steel Corrosion Products Formed in Tropical Marine Environments of Panama

A low-carbon steel A-36 and two conventional weathering steels A-588 and COR-420 exposed at four atmospheric test stations located in (i) Tocumen, an urban site near the Pacific Ocean, (ii) Sherman-Open, (iii) Sherman-Coastal, and (iv) Sherman-Breakwater on the Caribbean coast of Panama. Kinetics of the short-term atmospheric corrosion process and the relationship with exposure time and environmental characteristics of each site were investigated. The atmospheric exposure conditions, particularly the time of wetness, deposition of chloride, and the washing effect of contaminants on the metal surface by rain are of upmost importance in determining the corrosion behaviour and composition of rust. The corrosion products were mainly identified using room temperature and low temperature (80 K) Mössbauer spectroscopy, FTIR, and X-ray powder diffraction. In all samples,γ-FeOOH andα-FeOOH were the main constituents. Maghemite (γ-Fe2O3), magnetite (Fe3O4), and Akaganeite (β-FeOOH) were also identified.

Atmospheric corrosion of mild steel

The atmospheric corrosion of mild steel is an extensive topic that has been studied by many authors in different regions throughout the world. This compilation paper incorporates relevant publications on the subject, in particular about the nature of atmospheric corrosion products, mechanisms of atmospheric corrosion and kinetics of the atmospheric corrosion process, paying special attention to two matters upon which relatively less information has been published: a) the morphology of steel corrosion products and corrosion product layers; and b) long-term atmospheric corrosion ( > 10 years).

Characterization of oxides of stainless steel UNS S30400 formed in offshore environment

Thick corrosion products of austenitic stainless steel obtained from a steam turbine structure exposed in offshore environment were studied by optical stereomicroscopy, X-ray diffraction, Mössbauer and energy-dispersive X-ray spectroscopy. The external surface of mechanical structure was exposed to a marine atmosphere and the internal one to a combustion gas for two decades. Characterization of corrosion products showed high content of akaganeite in the outer region and a mixture of akaganeite and hematite in the inner surface. Besides these characteristics, a distribution of nanosized superparamagnetic particles of akaganeite was found in the rusts.

Corrosion Behavior of TP95S Anti-Sulfur Casing Steel in High Temperature High Pressure H<sub>2</sub>S/CO<sub>2</sub> Environment

The anti-corrosion performance of Tiangang TP95S casing steel was studied by high temperature autoclaves simulating the high-temperature and high-pressure H2S/CO2 environment. The experimental results show that the corrosion rates increase with the rising of temperature which is from 40°C to 80°C under the dynamic and static conditions of the simulated environments; the dynamic corrosion rates are between 1.7294 and 1.8601mm/a and the corrosion rates are 0.4264～1.2715mm/a under the static conditions, both of which belong to a serious corrosion category; the dynamic corrosion samples have had the localized corrosion at 40°C, but the local corrosion of the static corrosion specimens appeared at 80°C; the corrosion product of TP95S steel takes FeS as the core in the case of static corrosion at 40°C.

Explosion of ammonium nitrate solutions, two case studies

Two ammonium nitrate solution explosion accidents are analyzed in terms of the boiling point and solubility data. Both accidents occurred following a prolonged stoppage. In both cases a local increase in concentration and/or crystallization of ammonium nitrate has been suspected. In the first case this has been due to loss of temperature control with consequent evaporation under vacuum. In the second case crystal formation was attributed to cooling crystallization owing to poor insulation. Other conditions increasing the likelihood of the explosion were also satisfied. These include lack of flow, increase in temperature, and catalysis by both increased solution acidity and the presence of stainless steel corrosion products.

Studies of galvanised steel atmospheric corrosion in Saudi Arabia

This paper summarises the results obtained for galvanised steel specimens exposed in Saudi Arabia region for four years at four pure marine and five mixed marine (SO2 polluted) sites. The atmospheres at these sites were characterised climatologically and in terms of their pollution level so that their corrosivity could be expressed in accordance with ISO standards. Chemical characterisation of the galvanised steel corrosion product layers was performed using X-ray diffraction. The main phases determined were zincite (ZnO), simonkolleite [Zn5(OH)8Cl2.H2O], smithsonite (ZnCO3), magnetite (Fe3O4), gordaite [NaZn4(SO4)Cl(OH)6Cl.6(H2O)], hematite (Fe2O3), zinkosite (ZnSO4), zinc chloride (ZnCl2), zinc hydroxide sulphate hydrate [(Zn(OH)2)3(ZnSO4)(H2O)3] and zinc sulphate hydroxide hydrate [ZnSO4(OH)2.5H2O] was found on the specimens. The results obeyed well with the empirical kinetics equation of the form C = Ktn, where K and C are the corrosion losses in mg cm−2 after 1 and ‘t’ years of the exposure respectively, and ‘n’ is constant. Based on ‘n’ values, the corrosion mechanism of galvanised steel is predicted. The results obtained show that the corrosion rate of galvanised steel is a function of both the chloride, SO2 pollution level and the humidity. Corrosion rate of galvanised steel specimens have been obtained by loss of weight after each year of exposure.

A new steel with good low‐temperature sulfuric acid dew point corrosion resistance

AbstractIn this work, new steels (1#, 2#, and 3#) were developed for low‐temperature sulfuric acid dew point corrosion. The mass loss rate, macro‐ and micro‐morphologies and compositions of corrosion products of new steels in 10, 30, and 50% H2SO4 solutions at its corresponding dew points were investigated by immersion test, scanning electron microscopy (SEM) and energy‐dispersive spectrometry (EDS). The results indicated that mass loss rate of all the tested steels first strongly increased and then decreased as H2SO4 concentration increased, which reached maximum at 30%. Corrosion resistance of 2# steel is the best among all specimens due to its fine and homogeneous morphologies of corrosion products. The electrochemical corrosion properties of new steels in 10 and 30% H2SO4 solutions at its corresponding dew points were studied by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The results demonstrated that corrosion resistance of 2# steel is the best among all the experimental samples due to its lowest corrosion current density and highest charge transfer resistance, which is consistent with the results obtained from immersion tests.

In situ Raman spectroscopy study of corrosion products on the surface of carbon steel in solution containing Cl − and [formula omitted

Corrosion products of carbon steel in a simulated solution containing Cl − and SO 4 2 - were investigated by in situ Raman spectroscopy with a self-designed device. The results of Raman test and the SEM/EDS analysis of samples in different immersion times indicate that the corrosion products on the surface of the carbon steel consist of double rust layers, i.e. a porous outer layer (lepidocrocite γ-FeOOH) and a compact inner layer (magnetite Fe 3O 4). Aggressive ions such as Cl − and SO 4 2 - promote corrosion leading to the formation of lepidocrocite γ-FeOOH. Weight loss vs. time curve was also measured to study the effects of corrosion products. Corrosion products on a parallel sample were tested by Raman spectroscopy in air environment, which shown a distinct result from the one of in situ test.

INFLUENCE OF pH VALUES AND CORROSION PRODUCTS ON LOW CARBON STEEL CORROSION SUSCEPTIBILITY IN BORATE BUFFER SOLUTION

Low carbon steel has been studied as one candidate material of the outer container used in the geological disposal of the high-level radioactive nuclear waste. The active/passive state of the steel is the most important factor in maintaining the service life of the container. The active state will ensure that the container achieve the designed life under general corrosion, and moreover, the passive state will degrade the container's life under stress corrosion cracking (SCC) caused by pitting corrosion. In the groundwater, a lot of chemical compositions have very complicated effects on the active/passive state of the low carbon steel. Among these factors, obviously, the pH values of the ground water and the corrosion products of the low carbon steel would be the most important factors. In this paper, the influences of pH values and corrosion products on the susceptibility of the low carbon steel in the deaerated borate buffer solutions were studied. The results showed that the corrosion product did not change the corrosion potential of the low carbon steel at a pH value of 8, which means that the steel was in the active state, while the corrosion product made the corrosion potentials of low carbon steel move to the passive state at pH values of 9 and 10. XPS and XRD analyses indicated that the corrosion products were composed of Fe6(OH)12B4O7 and γ-FeOOH. The low carbon steel with corrosion products was passivated more easily than the naked steel substrate.

Morphology of corrosion products of steel in concrete under macro‐cell and self‐corrosion conditions

AbstractIn this paper investigations into the formation of specific corrosion products during the process of chloride induced corrosion of steel in concrete are presented. The extension of corrosion products within concrete was established by means of X‐ray tomography analyses. Then a detailed analysis of the nature of corrosion products has been conducted by means of Raman micro‐spectroscopy and energy dispersive spectroscopy. Results emphasize two different corrosion patterns. The first one is composed of shallow cavities, where mostly magnetite and goethite were identified, traducing aerated to moderate aerated conditions in these media. The second pattern was identified as deep, needle‐like pits, where chlorinated‐iron‐oxides phases were present associated with more or less important chloride enrichments. The presence of these particular species is indicating low redox and low pH conditions within these pits.

Spectroelectrochemical Study of Stainless Steel Corrosion in NaCl-KCl Melt

High-temperature spectroelectrochemestry was applied to study corrosion of various types of stainless steel in molten salts. The electronic absorption spectra of products of anodic dissolution of stainless steel major components (iron, chromium, nickel, molybdenum, manganese, titanium) were measured in NaCl-KCl melt at 750 °C. The effectiveness and limitations of applying spectroscopic method for studying alloys corrosion was demonstrated on example of anodic dissolution of AISI 316L, 316Ti and 321 austenitic steels. The major corrosion products of steels are iron, manganese and chromium species. Prolongation of anodic dissolution leads to increasing chromium-to-iron ratio in the melt. Titanium in steels forms very stable carbonitride species that aren't dissolved during anodic oxidation.

Exposure testing of fasteners in preservative treated wood: Gravimetric corrosion rates and corrosion product analyses

Research was conducted to determine the corrosion rates of metals in preservative treated wood and also understand the mechanism of metal corrosion in treated wood. Steel and hot-dip galvanized steel fasteners were embedded in wood treated with one of six preservative treatments and exposed to 27 °C at 100% relative humidity for 1 year. The corrosion rate was determined gravimetrically and the corrosion products were analyzed with scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction. Although the accepted mechanism of corrosion in treated wood involves the reduction of cupric ions from the wood preservative, no reduced copper was found on the corrosion surfaces. The galvanized corrosion products contained sulfates, whereas the steel corrosion products consisted of iron oxides and hydroxides. The possible implications and limitations of this research on fasteners used in building applications are discussed.

Ab initio density functional theory + U predictions of the shear response of iron oxides

The products of steel corrosion in moist air are α-Fe 2O 3, FeO, and Fe 3O 4. Here we employ an ab initio density functional theory + U method to predict the shear properties of these oxides, to gain insight into failure mechanisms of oxide scales that form on steel. A renormalization model proposed by Mosey and Carter is employed to extrapolate atomic scale shear strengths to those of macroscopic sample sizes. The extrapolated macroscopic predictions are consistent with experimental measurements. The shear strengths of FeO and Fe 3O 4 are predicted to be similar, ∼4.5 MPa, while the shear strength of α-Fe 2O 3 is predicted to be the largest, ∼7 MPa, for samples 5 mm thick. The preferred slip systems are predicted to be {0 0 0 1}〈1 0 1 ¯ 0〉 for α-Fe 2O 3 and {1 1 0}〈1 1 ¯ 0〉 for both FeO and Fe 3O 4. These shear strengths are significantly lower than the corresponding tensile strengths, suggesting that these oxide scales are likely to slip before fracturing.

Electrochemical Corrosion of STS304 Acupuncture Needles by Electrical Stimulation

We present the first investigation of electrical corrosion in acupuncture needles after electrical stimulation. Using scanning electron microscopy, we observed the occurrence of electrochemical corrosion on the surface of stainless steel 304 acupuncture needles after electrical stimulation in the tibial muscles of rats. Biphasic pulse electrical stimuli with 10-Hz frequency, 1-mA intensity and 1-ms pulse width were applied to the needles. The terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) method labels fragmented DNA. Positive staining using this test indicates apoptotic cells in electrically stimulated tissues. The risk of electrical corrosion was found to be less in bipolar, short-duration, low-current or voltage and short-period stimulation than in monopolar, long-duration, high-current or voltage and long-period stimulation. Evaluation with a scanning electron microscope revealed that electrical stimulation can increase the electrical corrosion of stainless steel 304 acupuncture needles. In biocompatibility studies of stainless steel 304 acupuncture needles for electrical stimulation, TUNEL-positive cells were detected in the tibial muscle within 5 days after electrical stimulation. The results of this study demonstrate that the corrosion products of stainless steel 304 acupuncture needles might affect the post-electrical stimulation tissue response.

Ab initio DFT + U predictions of tensile properties of iron oxides

Stress-corrosion cracking of steel is a ubiquitous phenomenon in which steel is chemically corroded, followed by fracture induced by applied loads. The products of steel corrosion in moist air at high temperature (>570 °C) are α-Fe2O3, FeO, and Fe3O4. Here we employ an ab initio density functional theory + U method to predict the tensile properties of these oxides, to gain insight into failure mechanisms. The universal binding energy relationship of Hayes et al. is employed to extrapolate atomic scale data to macroscopic sample sizes. The extrapolated macroscopic predictions are consistent with experimental measurements. The ordering of tensile strengths is shown to be FeO < Fe3O4 < α-Fe2O3, which correlates with increasing ionicity (as given by the formal charge on the Fe cations) in the three oxides. The direction that has weakest tensile strength is predicted to be along [01 (3/2)(a/c)22] for α-Fe2O3 and along [001] for both FeO and Fe3O4. The direction dependence of tensile properties for these three iron oxides can be understood via a local bond strain analysis. We also predict that loading FeO along [110] and Fe3O4 along [001] or [111] produces a plastic response prior to brittle fracture at high temperature.