Amount Of Corrosion Research Articles

Experimental Investigation on Crack Initiation and Propagation Due to Corrosion of Reinforcement

Abstract In this research, an investigation was carried out through experimentation to explore the mechanism of concrete cover cracking because of expansive pressure induced by corrosion products. The study aimed to monitor structural health by monitoring the crack width and crack propagation in the cover concrete so that the level of corrosion might be discovered. Concrete prisms of 200 by 200 by 300 mm reinforced with 60-grade 12-mm-Ø plain mild steel bar were used to simulate reinforced concrete beams having various cover thicknesses of 20, 37.5, 50, and 75 mm, respectively, to observe the mechanism of crack initiation, propagation, and level of corrosion with respect to the width of surface crack. The level of corrosion was measured in mg/cm2 following Faraday’s law and by gravimetric loss method, and the width of crack was measured by image analysis. For a cover thickness up to 37.5 mm, crack was initiated from the outer face and propagated inward, whereas for a cover thickness of 50 mm and greater, crack was initiated at the steel-concrete interface and propagated outward. A linear relationship was found between crack width and level of corrosion. For cover thicknesses of 20 and 37.5 mm, the critical corrosion amount (CCA) needed to initiate crack was about 22 mg/cm2. However, a sudden increase in CCA was noticed when the cover thickness was 50 mm and greater. For a cover thicknesses of 50 mm and 75 mm, the CCA values were 129 and 211 mg/cm2, respectively.

Development of discrete meso-scale bond model for corrosion damage at steel-concrete interface based on tests with/without concrete damage

Rebar corrosion can lead to significant deterioration in bond strength between steel and concrete. However, since confinement is lost as the concrete cracks, the changes in frictional bonding and mechanical bonding resulting from corrosion remain unclear and there is a need for an efficient tool that can evaluate the bond performance of corroded concrete structures. In this study, an innovative pull-out test is used to study changes in bonding in reinforced concrete after rebar corrosion, then a discrete meso-scale model based on the Rigid Body Spring Model (RBSM) is developed to simulate the observed bond behavior. To isolate the effects of concrete cracking, after an initial pull-out test, the corroded rebars are obtained and used as the reinforcement in newly cast sound specimens that are subject to a further pull-out test. A corrosion acceleration method is used to obtain corroded rebars. Different types of reinforcement (round rebars and deformed rebars) are studied. The results are used to study changes in frictional bonding and mechanical bonding at different degrees of corrosion. It is found that, without concrete cracking, the frictional bond in specimens with both round and deformed rebars significantly increases with the amount of corrosion, while total bond strength of specimens with deformed bar is almost unchanged because mechanical bonding is weakened. In the presence of concrete cracking, for specimens reinforced with a corroded round rebar, bond capacity increases initially (up to 3% corrosion) and then falls as corrosion increases, while bonding in those with a corroded deformed rebar shows a consistent decrease. In the RBSM-based simulations, the effect of corrosion is modeled by adjusting springs at the corroded interface. Constitutive models of shear and normal springs are developed to simulate corrosion and reflect the changes on frictional and mechanical bonding. Simulated results for load-displacement relationship, pull-out capacity and crack pattern are in good agreement with the experimental results. The numerical simulation is used to visualize internal stress development and strain distribution along the rebar as the degree of corrosion increases, a result that cannot be obtained by experimental methods. The results demonstrate that RBSM is a useful tool for evaluating the mechanical performance of corroded reinforced concrete structures.

An Investigation on the Usability of Acceleration Test by Impressed Anodic Current for Evaluating Corrosion Behavior of Hot-Dip Galvanized Rebar in Concrete.

Hot-dip Galvanized rebar (hereafter, HDG rebar) has an anti-corrosion effect due to the sacrificial anodic reaction of zinc. Additionally, the zinc coating itself provides barrier protection for the steel substrate. Meanwhile, from one of the investigations on the field performance of HDG rebar in concrete, HDG rebar did not protect the substrate when the remaining zinc was under 50 µm. For the evaluation of this property over a short period of time, an acceleration test using impressed anodic current (hereafter, acceleration test) may be useful. This test impresses constant direct current into the rebar and can result in the intended quantitative extent of the anodic reaction. However, in using this test on HDG rebar, it was found that the high rate of applied current density could cause an unintended early end of the anti-corrosion effect of zinc, despite there being more than 50 µm of remaining zinc thickness. In this study, the usability of the acceleration test was investigated to determine if it is a suitable method for evaluating the anti-corrosion behavior of HDG rebar in concrete. As a test variable, a comparatively low rate of applied current density was used in the experiments. As a result, it was clarified that an effective corrosion protection of the substrate was made with an increase of the zinc corrosion amount. This anti-corrosion effect was similar to that known to exist in actual corrosion environments. This behavior was terminated when the concrete cracked, and the substrate became corroded. While the test condition in this study resulted in an early end of the anti-corrosion effect of zinc, a linear correlation was achieved between the applied current density and the remaining zinc thickness at the time that the anti-corrosion effect was terminated. It was found that lowering the applied current density resulted in a more suitable test condition. In conclusion, the acceleration test was found to be useful, although further experimental validation is necessary to confirm this finding.

Utilization of Water Utility Lime Sludge for Flue Gas Desulfurization in Coal-Fired Power Plants: Part III. Testing at a Higher Scale and Assessment of Selected Potential Operational Issues.

The feasibility of lime sludge utilization for flue gas desulfurization was evaluated by continuing the previous laboratory-scale studies at a higher scale and investigating two potential operational issues, namely viscosity and metal corrosion. Two lime sludge samples and a baseline limestone sample, which were previously characterized and tested for SO2 capture from a simulated flue gas at a laboratory scale, were first tested at a 10-fold scale with a simulated flue gas, and then tested with a slipstream of flue gas from a coal-fired power plant. The tested lime sludge and limestone slurries reduced the SO2 concentration of the simulated flue gas from 2000 to <1 ppm, and they demonstrated similar Hg reemission profiles. Field-testing results revealed that the limestone and lime sludge slurries reduced the SO2 concentration of the flue gas from ~1500 to <1 ppm. These experiments confirmed our previous smaller scale laboratory results that lime sludge can function as a suitable substitute for limestone for SO2 removal from the flue gas of coal-fired power plants without negatively affecting Hg reemission. Two operational issues, namely viscosity and metal corrosion, were investigated to evaluate practical issues in the transition from limestone to lime sludge at power plants. Results of Marsh funnel viscosity experiments conducted at different solids contents and temperatures indicated the limestone and lime sludge slurries and their gypsum counterparts had similar flow characteristics. Carbon-steel, stainless-steel, and Hastelloy coupons were tested for corrosion by lime sludge and limestone slurries. Both stainless steel and Hastelloy were resistive to corrosion in slurries made from lime sludge or limestone samples or their gypsum counterparts. A considerable but similar amount of corrosion was observed for carbon-steel coupons exposed to lime sludge and limestone slurries. Adding 5000 ppm of Cl- to slurries considerably increased the corrosion rate of carbon steel.

Study of Corrosion Penetration Rate on Composite Materials EN AC-43100 (AlSi10Mg (b)) + SiC*

Corrosion Penetration Rate (CPR) is defined in three ways: (1) the speed at which any metal in a specific environment deteriorates due to a chemical reaction in the metal when it is exposed to a corrosive environment, (2) the amount of corrosion lossed per year in thickness, (3) the speed at which corrosion spreads to the inner portions of a material. The purpose of this research is calculations CPR of Aluminum matrix composite materials (AlSi10Mg (b)) with Silicon carbide (SiC*) reinforcement. A wet corrosion test was conducted where the AlSi10Mg(b) and AlSi10Mg(b)+SiC* were dipped in a solution of HCl acid, NaOH, NaCl and in pH solution 1,3,5,7,9,11, and 13. It was found that the highest corrosion penetration rate occured when the specimen dipped on HCl solution and in pH 1 It was also found that the addition of SiC* can reduce rate of corrosion in materials. Finally, this study showed that composite material, AC-43100 (AlSi10Mg (b)) 85% + 15% SiC*, was the best material in resist of corrosion attack, has smallest CPR below the standard corrosion <0.5 mm / yr.

Experimental behavior and analytical modeling of corroded steel rebars under compression

The durability of reinforced concrete structures can be sharply reduced by the corrosion of the steel rebars. This phenomenon is of great concern, since it is one of main cause of degradation in RC structures, almost in non-exceptional conditions. Furthermore, the corrosion effects can influence the seismic behavior, leading to dangerous strain localizations and variations of strength distribution and rotation capacity. This problem is amplified if, due to the corrosion of the reinforcement, longitudinal and/or transversal, the buckling of the steel bars takes place. Main aim of the paper is the evaluation of the influence of the corrosion on the compressive and buckling behavior of corroded steel reinforcement bars. At the scope, a comprehensive experimental survey has been planned and performed, for different values of steel bar length-to-diameter ratios and different amount of corrosion. Furthermore, based on the obtained outcomes, a simplified analytical model is developed for the definition of the constitutive relationships of corroded bars under compression.

An electromechanical impedance-instrumented corrosion-measuring probe

Corrosion of metallic structures widely existed in multiple industries, such as oil and gas, civil infrastructure, aerospace, mechanical, mining, and processing. Current available corrosion-monitoring methods are based on different sensing principles, which have their own advantages, and some drawbacks that may limit their application on some aspects. This article presents an electromechanical impedance-instrumented corrosion-measuring probe for corrosion monitoring. The proposed probe is fabricated by attaching a circular lead zirconate titanate patch onto a metal rod. Compared to other electromechanical impedance-based corrosion-monitoring methods, the probe is capable of isolating the influence of structural complexity, variations in loading and boundary conditions. Five probes were fabricated in the experimental study and three of them were subjected to accelerated corrosion tests to mimic the corrosion-induced mass loss damage. Results showed that the peak magnitude of the conductance signatures was reduced with the increase in corrosion amount. The variations in the conductance signatures were quantified by three statistical quantifying metrics, that is, root-mean-square deviation, mean absolute percentage deviation, and correlation coefficient deviation. All these metrics increase with the increase in corrosion amount, which can be used as an indicator of the corrosion process. This study proves that the proposed corrosion-measuring probe is effective in monitoring corrosion and shows promising application potential. This research also serves as a proof-of-concept study to demonstrate the capability of the electromechanical impedance technique in monitoring mass loss due to corrosion.

Effects of Environmental Conditions on Cathode Degradation of Polymer Electrolyte Fuel Cell during Potential Cycle

We investigated the effects of cell temperature and the humidity of gas supplied to the cell during the load cycle durability test protocol recommended by The Fuel Cell Commercialization Conference of Japan (FCCJ). Changes in the electrochemically active surface area (ECA) and in the amount of carbon support corrosion were examined by using the JARI standard single cell. The ECA declined more quickly when the gas humidity was raised, and the carbon corrosion was at the same level. These results suggest that the agglomeration of platinum was accelerated by the same agglomeration mechanism, i.e., by raising the humidity of the gas supplied to the cell.

Time-dependent Seismic Performance Assessment of Corroded Reinforced Concrete Frames

In this study, effects of reinforcement corrosion such as reinforcement cross section reduction, steel yield strength and concrete compressive strength reduction on RC member capacity decrease are studied. Next, a two-dimensional reinforced concrete moment resistant frame is modeled to evaluate the effects of moderate and severe intensity corrosion on moment-curvature behavior of elements and structure seismic response under nonlinear analysis. Structure capacity curves in push-over analysis and failure curves resulted from IDA for both the structure without and with corrosion are obtained and the effects of reinforcement’s corrosion on the reinforced concrete frame seismic performance are determined through comparing the results. The results revealed that in terms of amount, place and type of corrosion in the reinforced concrete frame, value of the reduction resisting moment of elements is different. Furthermore, the outcomes of nonlinear analyses showed that the capacity of structure is reduced and its seismic performance level is changed as a result of corrosion.

Effect of Microstructures on the Corrosion Behavior of Reinforcing Bars (Rebar) Embedded in Concrete

This work aims at understanding the effect of microstructures (coarse, medium and fine ferrite–pearlite, martensite and tempered martensite) of a reinforced (rebar) steel developed by various heat-treatments (furnace cooling, air-cooling, force air-cooling, quenching, and tempering, respectively) on its corrosion behavior in freely aerated 3.5% NaCl + 3.5% FeCl3 solution. The impressed current technique was used for forcing corrosion of the rebar, which was embedded in concrete coupon, so that correlation could be drawn between microstructure and corrosion behavior in short duration. Corrosion susceptibility increased from force air-cooled–quenched–air cooled–furnace cooled–tempered steels. The crack formation in the concrete was directly related to the rust composition and thickness, presence of crack in the rust, alpha/gamma* ratio and critical corrosion amount.

PZT based smart corrosion coupon using electromechanical impedance

Abstract Corrosion induced material loss in metallic structures is a widespread and urgent problem across multiple industries. In this paper, a novel corrosion monitoring method is proposed based on the lead zirconate titanate (PZT) based smart corrosion coupon (SCC) using electromechanical impedance (EMI). The basic idea of the corrosion monitoring method is that the corrosion induced thickness loss of the SCC will leads to the variation in the EMI signatures. The SCC was fabricated by bonding a PZT patch onto a corrosion coupon. The EMI signatures of the SCC under different corrosion amount were acquired and analyzed. Results showed that the peaks in the conductance signatures present a leftward shift and the peak frequencies decrease linearly with increase of the corrosion amount. To obtain more insight into SCC electromechanical system, the finite element analysis were also performed to study the EMI response and modal characteristics. The simulation results agreed well with experimental results. And it was found that the coupled bending modes are very sensitive to the corrosion induced thickness loss. The proposed smart corrosion coupon is cost effective, capable of determining corrosion amount quantitatively, and has promising application potential.

Do oxidized zirconium heads decrease tribocorrosion in total hip arthroplasty? A study of retrieved components.

The aim of this study was to evaluate fretting and corrosion in retrieved oxidized zirconium (OxZr; OXINIUM, Smith & Nephew, Memphis, Tennessee) femoral heads and compare the results with those from a matched cohort of cobalt-chromium (CoCr) femoral heads. A total of 28 OxZr femoral heads were retrieved during revision total hip arthroplasty (THA) and matched to 28 retrieved CoCr heads according to patient demographics. The mean age at index was 56 years (46 to 83) in the OxZr group and 70 years (46 to 92) in the CoCr group. Fretting and corrosion scores of the female taper of the heads were measured according to the modified Goldberg scoring method. The OxZr-retrieved femoral heads showed significantly lower mean corrosion scores than the CoCr heads (1.3 (1 to 2.75) vs 2.1 (1 to 4); p < 0.01). Mean fretting scores were also significantly lower in the OxZr cohort when compared with the CoCr cohort (1.3 (1 to 2) vs 1.5 (1 to 2.25); p = 0.02). OxZr heads had more damage in the proximal region compared with the distal region of the head. Location had no impact on damage of CoCr heads. A trend towards increased corrosion in large heads was seen only in the CoCr heads, although this was not statistically significant. Retrieval analysis of OxZr femoral heads showed a decreased amount of fretting and corrosion compared with CoCr femoral heads. OxZr seems to be effective at reducing taper damage. Cite this article: Bone Joint J 2019;101-B:386-389.

A Study of Estimating the Amount of Corrosion to Steel Plates of Oil Storage Tanks in Bai-Hassan Oil Field in Kirkuk

A Study of Estimating the Amount of Corrosion to Steel Plates of Oil Storage Tanks in Bai-Hassan Oil Field in Kirkuk

An experimental study on the corrosion characteristics of the karst tunnel engineering area in Southwest China

The construction and protection of tunnels in karst areas face many difficulties and challenges. The Wulong tunnel, which is located in a karst area in Southwest China, was s elected as an case study to analyze and evaluate the corrosion of tunnel rock under different environmental conditions. A series of field and laboratory experiments aimed at studying the impact of temperature and flow rate on tunnel rock corrosion was conducted, and the results were analyzed in terms of total corrosion amount, corrosion rate, and the features and mechanisms of the chemical and physical corrosion processes. The key factors affecting the chemical and physical corrosion processes were also determined. A mathematical expression for the corrosion rate as a function of the flow rate and temperature was constructed from the experimental results, and this mathematical model was then used to analyze tunnel rock corrosion under field environmental conditions.

Applicability Analysis of Assessment Methods for Morphological Parameters of Corroded Steel Bars.

The irregular and uneven residual sections along the length of a corroded steel bar substantially change its mechanical properties and significantly dominate the safety and performance of an existing concrete structure. As a result, it is important to measure the geometry and amount of corrosion of a steel bar in a structure properly to assess the residual bearing capacity and service life of the structure. This paper introduces and compares five different methods for measuring the geometry and amount of corrosion of a steel bar. A single 500 mm long and 14 mm diameter steel bar is the specimen that is subjected to accelerated corrosion in this protocol. Its morphology and the amount of corrosion were carefully measured before and after using mass loss measurements, a Vernier caliper, drainage measurements, 3D scanning, and X-ray micro-computed tomography (XCT). The applicability and suitability of these different methods were then evaluated. The results show that the Vernier caliper is the best choice for measuring the morphology of a non-corroded bar, while 3D scanning is the most suitable for quantifying the morphology of a corroded bar.

Load bearing of corroded shells under external/internal pressure

ABSTRACTThe paper examines the effects of axisymmetric, corrosion-induced, wall thinning on load bearing (buckling, collapse, plastic instability) of domed closures. It is assumed that the wall is corroded on inside only. Details are provided for torispherical closures with additional results for ellipsoidal heads. For torispherical domes, the ratio of corroded wall thickness, tc, to non-corroded thickness, t, is varied between 0.10 ≤ tc/t ≤ 1.0. Three modelling scenarios are considered: (1) corrosion confined to the knuckle, (2) corrosion spanning evenly the knuckle and spherical parts and (3) patch-type area positioned at the apex. The factors influencing load bearing capacity were found to be (1) meridional position of corroded area, (2) depth of corrosion itself and (3) meridional span of corroded wall. The largest drop of load bearing capacity is found when corroded wall is at the knuckle/crown junction (“buckling zone”). It is shown that assessment of load carrying capacity based on collapse mechanism is not only wrong but dangerous. Sensitivity of buckling strength to the amount of corrosion shows similar trends under internal or external pressure. Load bearing capabilities are also assessed for prolate and oblate ellipsoidal heads. Performance of the latter is compared with performance of Korbbogen dome – frequently found in industry.

The effect of atmospheric precipitation on the corrosion of ferrous metals buried in soils

ABSTRACTData from the US NBS study for corrosion of buried objects are employed to show that average annual atmospheric precipitation directly influences corrosion of ferrous objects buried in various soils. This is attributed to the softness of precipitation waters and their delivery of oxygen. Also, as surrogate for time of wetness at the buried object within the soil, atmospheric precipitation has a clearer effect on corrosion loss and localised corrosion than does ground surface time of wetness. The relationship and the amount of corrosion also depend on soil type, a matter not previously considered. The results allow an explanation for the generally higher rate of corrosion of cast iron water pipes in cities such as Sydney with mainly clay-loam soil backfill and high precipitation compared with many locations in the UK with much lower annual average precipitation.

Using RH Sensitivity to Estimate Carbon Support Loss in PEMFC Electrodes

The carbon blacks typically used for catalyst supports in proton exchange membrane fuel cells (PEMFCs) are vulnerable to oxidation at high cell potential. Carbon lost to corrosion will lead to performance degradation from the reduced electrochemical surface area (ECSA) and an eventual collapse of electrode structure and porosity. Therefore, PEMFC stacks must be protected from potential excursions by a range of operational strategies. During the development of fuel cell systems, carbon support loss is often evaluated after cell failure has already occurred, using destructive methods such as cross sectioning and SEM imaging of the electrode thickness. The goal of the present work is to advance a non-destructive in situ test method for early estimate of moderate carbon loss. Such measurement allows the effectiveness of mitigation to be compared in a shorter time before running a stack to failure. For the present tests, carbon oxidation in membrane electrode assemblies (MEAs) is quantified by measuring CO2 concentration in the exhaust gas during high potential excursions. Carbon loss is compared with the performance (current density at constant cell potential) as a function of inlet gas relative humidity - an RH sensitivity curve. The RH sensitivity at low power (Figure 1) is found to be highly responsive to moderate amounts of carbon corrosion. The current at high humidity decreases along with total ECSA, but the current at low humidity increases. The performance difference below 60% RH is sufficiently repeatable to be used for a calibrated indicator of carbon mass loss. An experimental design was executed to optimize test conditions to produce a linear response with respect to carbon loss (Figure 2). Other details of applying this method are discussed. A brief investigation of the mechanism for shifting RH sensitivity is also included. Oxygen reduction reaction (ORR) mass activity under dry conditions is found to increase after moderate corrosion of carbon. CO stripping measurements indicate that a greater portion of the catalyst area stays active at low humidity following corrosion. Finally, the behavior of electrodes with different carbon supports was compared. A porous high surface area carbon (HSAC) support showed the increase in dry performance as described above, while a relatively non-porous Vulcan-style support showed little change in RH sensitivity as a function of carbon loss. It is hypothesized that the HSAC pores become more hydrophilic as the carbon surface oxidizes. The hydrophilic pores would then help to maintain ionic conductivity to a greater fraction of catalyst particles under lower RH conditions. Figure 1

Corrosion behavior of low-carbon Cr micro-alloyed steel for grounding grids in simulated acidic soil

To improve the corrosion resistance of steels for grounding grids, a low-carbon Cr micro-alloyed steel was developed (C1 steel), and corrosion behavior of Q235 steel and newly developed C1 steel in simulated acidic soil was investigated. The corrosion rate was evaluated with the mass loss measurements, while the corrosion morphology of surface and cross section of rust layer was observed by scanning electron microscopy. The corrosion products were analyzed by energy-dispersive X-ray spectrometry, X-ray diffraction and X-ray photoelectron spectroscopy, and the polarization curve was measured using potentiodynamic polarization method. Results indicated that C1 steel displayed good corrosion resistance in the simulated acidic soil, of which the corrosion rate was only 30% of that of Q235 steel after corrosion for 360 h. The analysis of rust layer showed that lower carbon content in steel could reduce the tendency of micro cell corrosion and appropriate amount of chromium could improve the corrosion potential of metal matrix. Moreover, the analysis of X-ray photoelectron spectroscopy revealed that the chromium enriched in inner rust layer of C1 steel existed mainly in the form of Fe2CrO4, which facilitated the formation of Cr-goethite and improved the protection of corrosion products.

Numerical Investigation on Multiphase Erosion-Corrosion Problem of Steel of Apparatus at a Well Outlet in Natural Gas Production

The erosion-corrosion problem of gas well pipeline under gas–liquid two-phase fluid flow is crucial for the natural gas well production, where multiphase transport phenomena expose great influences on the feature of erosion-corrosion. A Eulerian–Eulerian two-fluid flow model is applied to deal with the three-dimensional gas–liquid two-phase erosion-corrosion problem and the chemical corrosion effects of the liquid droplets dissolved with CO2 on the wall are taken into consideration. The amount of erosion and chemical corrosion is predicted. The erosion-corrosion feature at different parts including expansion, contraction, step, screw sections, and bends along the well pipeline is numerically studied in detail. For dilute droplet flow, the interaction between flexible water droplets and pipeline walls under different operations is treated by different correlations according to the liquid droplet Reynolds numbers. An erosion-corrosion model is set up to address the local corrosion and erosion induced by the droplets impinging on the pipe surfaces. Three typical cases are studied and the mechanism of erosion-corrosion for different positions is investigated. It is explored by the numerical simulation that the erosion-corrosion changes with the practical production conditions: Under lower production rate, chemical corrosion is the main cause for erosion-corrosion; under higher production rate, erosion predominates greatly; and under very high production rate, erosion becomes the main cause. It is clarified that the parts including connection site of oil pipe, oil pipe set, and valve are the places where erosion-corrosion origins and becomes serious. The failure mechanism is explored and good comparison with field measurement is achieved.