Corrosion Of Steel Structures Research Articles

Axial compressive behavior of corroded H-shaped steel columns

The unpredictability of corrosion in steel structures, especially in H-section columns, is a topic that has received limited research attention. Using Monte Carlo simulation (MCS) and finite element analysis (FEA), this study investigates the effect of random pitting corrosion on H-section steel columns' ultimate bearing capacity under axial compression. In this study, MCS was employed to address the random distribution of pitting corrosion. The reliability of MCS and FEA was validated through existing literature on compression tests of H-shaped steel columns. To comprehensively assess the detrimental effects of pitting corrosion, a total of 3650 models of H-shaped columns, each exhibiting different pitting corrosion characteristics, were subjected to analysis. These models incorporated three corrosion parameters (volume loss rate, size, and depth) and two geometric parameters (slenderness and section size). A nonlinear buckling analysis was carried out to investigate the ultimate bearing capacity of the columns. The findings indicate that a volume loss rate of 20% can cause a decrease in the column's ultimate bearing capacity by approximately 50%. Furthermore, the study reveals that at equal volume loss rates, corrosion depth and slenderness significantly influence the reduction factor, while corrosion size and section size exert a minimal impact. As a result, this paper introduces a probabilistic assessment method for estimating the reduction factor in ultimate bearing capacity for H-section steel columns. Notably, with every 10% increase in the volume loss rate, the mean reduction factor in the ultimate bearing capacity decreases by approximately 0.12.

Performance assessment of corroded stiffened steel plates considering non-Gaussian spatial correlated corrosion random field

This paper investigates the effect of corrosion randomness on the compression performance of stiffened steel plates. An anisotropic non-Gaussian random filed model is proposed to characterize the corrosion depth of the corroded steel plate surface. The specimens of corroded steel plate were obtained utilizing the artificial climate environment method. Corrosion characteristics were measured through 3D-scanning and reverse modeling. Statistical methods are utilized to analyze corrosion depth, including probability distribution and correlation coefficient. Two models are proposed for steel plate placing flatly and inclinedly, respectively. It is found that for both models corrosion depth follows truncated GEV distribution, and the correlation coefficient follows a bidirectional exponential function. To investigate the effect of non-Gaussian and correlation characteristics on bearing capacity, the proposed model is used for generating anisotropic non-Gaussian corrosion random fields for stiffened steel plates. Generated samples were used for finite element analysis. It is found the ignorance of non-Gaussian or correlation of the corrosion depth field will underestimate the deterioration of bearing capacity of stiffened steel plates. Finally, a parametric study on the correlation coefficients of the corrosion field indicates that correlation length will affect the residual bearing capacity of corroded steel plate. The proposed random field for corrosion depth of steel plate could be used for potential application on the safety assessment of corroded steel structures.

Life-cycle assessment and prediction on ultimate capacity of corroded Q690 steel columns with H-section under bi-directional cyclic loading

The structures or structural members made of high-strength steel may have time-varying mechanical properties in whole life-cycle due to the ageing effects. In particular, the corroded steel structures in high-seismicity regions could have unexpected failure modes when subjected multi-directional excitations. Therefore, in this study, the mechanical properties of Q690 steel H-section columns during the life-cycle under bi-directional cyclic loads are investigated. Firstly, a refined finite element (FE) model is built, which takes the time-varying of corrosion characteristics into consideration. Then, the degradations of mechanical property and failure mechanisms of steel columns with different design parameters at whole life-cycle are analysed by the FE models. Finally, a quantitative calculation method of ultimate resistance and damage index of steel columns considering ageing effects is proposed. The findings demonstrate that several factors affect the ultimate strength of steel columns during the life-cycle stage, with the axial compression ratio and flange width-thickness ratio having the greatest impacts on the ultimate capacity. The ageing effect decreases the plastic flow capacity of steel columns, increases the stress concentration, and induces the failure mode transition from plastic flow to buckling failure. The ageing effect may be accurately estimated by the suggested calculation method for the ultimate capacity and damage index of steel columns at the life-cycle stage. The findings of this study highlight the significance of taking into account the ageing effects of steel columns in the seismic design.

Effect of Al Content on the Long-Term Corrosion Behavior of Arc-Sprayed ZnAl Alloy Coatings

The corrosion of steel structures in aggressive marine environments is a vital issue that induces significant degradation of their performance and lifespan. Herein, three arc-sprayed ZnAl coatings with varied Al contents of 0 wt.%, 15 wt.%, and 50 wt.% were deposited onto a hull steel substrate. The effect of Al content on the long-term corrosion protection performance of ZnAl coatings left in a chloride-containing solution for 840 h was systematically investigated. The evolutions of open-circuit potential, polarization curves, and electrochemical impedance spectroscopy of different ZnAl coatings during the long-term immersion test were examined. The morphologies and phase constitutions of the corrosion products were characterized. The results indicated that the corrosion rate of ZnAl coatings decreased as the Al content increased, and the ZnAl50 coating exhibited the most superior long-term corrosion protection performance. Moreover, for the three ZnAl coatings with an Al contents varying from 0 to 50%, their corrosion rate increased with immersion time in the initial 360 h due to the formation of the unstable and porous corrosion product ZnO; after 360 h immersion, their corrosion rate decreased with the prolonging of immersion time. This was revealed to be related to the formation of different corrosion products. ZnO and stable Al2O3 were the main corrosion products for the pure Zn coating and ZnAl15 coating, respectively. Al2O3 and powerful layered double hydroxide Zn6Al2(OH)16CO3·4H2O were found to be the dominant corrosion products of the ZnAl50 coating, which was responsible for its remarkable long-term corrosion protection performance.

The new insights towards smart pH-responsive anticorrosion coating based on HNTs carrying synergistic inhibitors: Experimental and molecular simulation

Corrosion of steel structures in reinforced concrete structures in coastal areas has long been an urgent concern. In this study, a combined corrosion inhibitor, consisting of benzotriazole (BTA) and sodium D-gluconate (SD), was loaded onto halloysite nanotubes (HNTs) using the vacuum negative pressure method. Then, the HNTs were encapsulated with biomass polyelectrolytes sodium alginate (SA) and chitosan (CS) by layer-by-layer self-assembly technique to prepare BTA/SD-HNTs@CS/SA (FHNTs) composite. Furtherly, a functional epoxy coating (FEP) with pH-responsive and long-term service ability was successfully fabricated. It is found that BTA/SD was released in large quantities under alkaline (pH = 11) and acidic (pH = 2) conditions, while essentially no release under neutral condition. The electrochemical impedance spectroscopy (EIS) measurements demonstrate that the corrosion protection ability of FEP was significantly stronger than pure epoxy coating (EP), and the addition of 2 % FHNTs having the most excellent anticorrosion performance with the maximum charge transfer resistance (Rct) value (4.8 × 106 Ω cm2) after 4 weeks of immersion, which was 2 orders of magnitude greater than the pure EP coating. Particularly, molecular dynamics (MD) simulations indicate that FEP coating has better barrier properties than EP, while the fractional free volume (FFV) value of H2O and Cl− in EP was 9.1 % and 5.1 %, respectively, whereas this value decreased by about 15 % to 7.7 % and 4.4 % in FEP. The results of density functional theory (DFT) calculations suggest that the released BTA and SD molecules have a synergistic adsorption effect on the surface, which can form a compact film to hinder the invasion of corrosive species. Overall, this study provides new insights for developing smart pH-responsive and superior anticorrosion coatings.

Fatigue stress concentrations analysis of real corroded steel structures based on replica imprints

AbstractThe service life of offshore support structures is significantly reduced by corrosion. In particular, pitting corrosion leads to high local stress concentrations and can reduce the expected fatigue strength. Previous studies on corroded specimens have shown that crack development in fatigue tests is correlated with stress concentration. In the context of maintenance of existing offshore wind turbines, there are novel efforts to capture the real surface geometry of corroded components with the so‐called replica technique, in which an imprint of the surface geometry is made and digitized with a 3D‐scanner and used to numerically analyse the stress concentrations due to pitting corrosion. In this study, it was shown that the replica technique is able to reproduce the effective stress concentrations of the original surface with very high accuracy.

Behaviour of corroded circular steel tube strengthened with external FRP tube grouting under eccentric loading: Numerical study

This paper uses ABAQUS software to perform finite element simulation on eccentric compression member of corroded circular steel tubes strengthened by FRP tube grouting. The working mechanisms, failure mode and the lifting of mechanical properties are investigated. The results show that the load–displacement curve of the member represents both bilinear and trilinear models. The former is in the overall buckling failure mode, while the latter is in the strength failure mode of the circular steel tube with bare ends. After strengthening, the bearing capacity increases by up to 114.99%. Moreover, the increase positively correlates with corrosion rate, grouting thickness, and FRP tube thickness. It first decreases before increasing as the slenderness ratio changes, while the concrete strength has little effect. At the same time, the bound flexural stiffness ratio is derived and provides reference suggestions for the practical engineering application of FRP tube grouting to strengthen corroded steel structures.

Study on hysteresis constitutive and fracture behaviors of corroded constructional steel under artificial atmospheric environment

In order to evaluate the seismic capacity of corroded steel structures in natural atmospheric environment, 18 steel plates with 6 corrosion ages obtained by artificial accelerated test were employed to the cyclic loading tests. A comprehensive corrosion parameter (D) considering the uniform and pitting corrosion was proposed, and used to study the effect of corrosion on the resistance and hysteretic behavior of corroded steel. The results showed that, with increase of D, both of the position of skeleton curves and the peak values of stress cycles were decreased significantly, the yield platform disappeared, and the elastic modulus and ultimate strength decreased sharply; D was also closely related to its energy-dissipating capacity. Then, D was applied to optimize the constitutive parameters and fracture parameters, and a Chaboche plastic constitutive (CPC) model was established to simulate the hysteretic behavior of corroded steel with very high accuracy. Besides, the relationships of fracture parameters (εpl and G) and D were also given. Finally, combined with fracture morphology, the fracture analysis of corroded steel under cycle load was performed. The dimples size on fracture was reduced with increase of D, the ductility would be degraded. While D greater than 4.8, the change rate of εpl and G showed a sudden change, that meant the fracture behavior tends to brittleness, and should be paid more attention to in the seismic reinforcement design of existing steel structure.

Evaluation of Corrosion Rate in X 65 Steel Pipes by Taguchi Method Based on Factors Originating from Soil and External Interactions

Steel pipelines that are used for the transportation of natural gas and petroleum usually pass through different places with different soil characteristics. Due to distinct soil structures and other corrosive factors, pipelines tend to corrode at different rates. In this study, the effects of moisture content, salt concentration, pH, AC potential and cathodic protection levels on the corrosion rate were investigated as factors affecting corrosion in steel structures originating from the ground and external sources. The number of experiments to be carried out was decided as a result of experimental design with the Taguchi statistical method. L16 orthogonal array was used for 4 different levels of 5 corrosion rate affecting factors and 16 different experimental studies were conducted to obtain corrosion rate values for each experiment. Based on the statistical analysis results, the effect of changes in moisture content of the soil on corrosion rate was higher compared to other factors. Considering that underground pipelines usually pass through neutral environments (pH levels between 6-8), the effect of changes in pH value on corrosion rate is less than the other factors studied. In addition, with the regression analysis performed through the Minitab software, a linear regression model and an equation was created to calculate the corrosion rates. Corrosion rate results obtained with the regression equation were compared with the test results performed in different test environments. By calculating the corrosion rate for different factors, selection of or changing the pipeline route, selection of material wall thickness, planning of pipeline control and maintenance periods can be made in the most ideal way. Also, a comparison of corrosion rates against existing literature shows that corrosion rates of steel materials change between outstanding classification ranges according to corrosion resistance classification of steel materials.

Role of 5 wt.% Mg Alloying in Al on Corrosion Characteristics of Al-Mg Coating Deposited by Plasma Arc Thermal Spray Process.

The corrosion of steel structures in coastal areas is a major issue. Therefore, in the present study, the protection against the corrosion of structural steel is carried out by depositing 100 μm thick Al and Al-5 Mg coatings using a plasma arc thermal spray process, immersing them in 3.5 wt.% NaCl solution for 41 days (d). To deposit such metals, one of the best known processes, arc thermal spray, is frequently used, but this process has severe defects and porosity. Thus, to minimize the porosity and defects of arc thermal spray, a plasma arc thermal spray process is developed. In this process, we used normal gas to create plasma instead of argon (Ar) and nitrogen (N2) with hydrogen (H) and helium (He). Al-5 Mg alloy coating exhibited uniform and dense morphology, where it reduced more than four times the porosity compared to Al, where Mg fills the voids of the coating, resulting in greater bond adhesion and hydrophobicity. The open circuit potential (OCP) of both coatings exhibited electropositive values due to the formation of native oxide in Al, while in the case of Al-5 Mg, the coating is dense and uniform. However, after 1 d of immersion, both coatings showed activation in OCP, owing to the dissolution of splat particles from the corner where the sharp edges are present in the Al coating, while Mg preferentially dissolved in the Al-5 Mg coating and made galvanic cells. Mg is galvanically more active than Al in the Al-5 Mg coating. Due to the capacity of the corrosion products to cover the pores and defects, both coatings stabilized the OCP after 13 d of immersion. The total impedance of the Al-5 Mg coating is gradually increased and is higher than the Al, which can be attributed to the uniform and dense coating morphology where Mg dissolves and agglomerates to form globular corrosion products and deposit over the surface, thereby causing barrier protection. The defect bearing corrosion products on Al coating led to the cause having a higher corrosion rate than the Al-5 Mg coating. A total of 5 wt.% mg in the Al coating improved the corrosion rate by a rate of 1.6 times compared to the pure Al in the 3.5 wt.% NaCl solution after 41 d of immersion.

A Method for Predicting the Corrosion Behavior of Structural Steel under Atmosphere

The durability and safety of steel structures during their life cycle are affected by steel corrosion. Limited test conditions and time hinder the reproduction of actual atmospheric steel corrosion. Most test studies have focused on the effect of pitting or uniform corrosion of steel structures, leading to the development of vague engineering methods that make it difficult to design steel structures with excellent corrosion resistance. In this study, a method involving three-dimensional cellular automata and a genetic algorithm was developed for predicting the corrosion behavior of structural steel. The calculation efficiency of three-dimensional cellular automata was improved by small iterative steps and adaptive activation for potential corrosion. Furthermore, the proposed method was tested with published tests, and the results showed that the method can simulate atmospheric corrosion with excellent accuracy and efficiency. The simulation results were used to calculate the structural steel cross-sectional performance with greater accuracy than that of the method of assuming uniform corrosion. Meanwhile, with accurate material parameters, the proposed method can also simulate the atmospheric corrosion of high-performance steel of different strengths and properties.

Automatic monitoring technology of salt spray corrosion of steel structure in coastal building construction

Automatic monitoring technology of salt spray corrosion of steel structure in coastal building construction

Nonlinear analysis of axial-compressed corroded circular steel pipes reinforced by FRP-casing grouting

In this paper, ABAQUS software is used to carry out finite element simulation on the axial compression performance of corroded round steel pipe members reinforced by FRP casing grouting. Moreover, its working mechanism and failure mode are analyzed. A typical load-displacement curve of the component is obtained. Furthermore, the effect of FRP pipe thickness, grouting thickness, corrosion rate, concrete strength, and slenderness ratio on the mechanical performance of the component is explored. The research results indicate that the component load-displacement curve can be characterized by bilinear and trilinear models. The former corresponds to the overall buckling failure mode, while the latter corresponds to the strength failure mode for the bare ends of a round steel tube. After reinforcement, the component bearing capacity increases up to 166.83%. Moreover, the increase is positively correlated with FRP pipe thickness, grouting thickness, and corrosion rate. The component bearing capacity first decreases and then increases when modifying the slenderness ratio, while concrete strength has a minor effect on it. Moreover, the bending stiffness ratio equation and the stability bearing capacity correction equation of the axial compression reinforced components are proposed. The aforementioned provides reference suggestions for practical engineering applications of corroded steel structures reinforced by FRP casing grouting.

Interfacial Bond-Slip Model for CFRP Plate Externally Bonded to Corroded Steel Plate

The purpose of this study is to establish the interfacial bond-slip model for CFRP plate externally bonded to corroded steel plate. The present bond-slip models for CFRP materials bonded to uncorroded steel plate were first reviewed. Thirty-four double-lap joints were tested to investigate the effect of corrosion duration and adhesive thickness on the bond behavior between CFRP plates and corroded steel plates, and the bond-slip curves for the bonding interface with different adhesive thickness and corrosion duration were obtained combined with the CFRP plate strain distribution data. A new bond-slip model for CFRP plate externally bonded to corroded steel plate was proposed, and the expression of the characteristic parameters, which included the maximum bond resistance τf, the relative slip at the peak bond stress s1, the fitting parameter α, and the interfacial fracture energy Gf, were also developed based on the careful regression analysis of the present data. The influence of the corrosion duration and construction adhesive thickness on the bond-slip relationship were accounted together and expressed as a new parameter; that is, the effective adhesive thickness teff. The comparison between the predicted values and experimental results indicated that the proposed bond-slip model can be applied to reproduce the structural response of the CFRP plate-corroded steel plate double-lap joint with reasonable accuracy. The outcome of this study can provide meaningful references and essential data for the reliable application of CFRP strengthening systems in the performance improvement of corroded steel structures.

Effect of Cathodic Protection Potential Fluctuations on the Corrosion of Low-Carbon Steels and Hydrogen Absorption by the Metal in Chloride Solutions with Nearly Neutral pH.

Considerable fluctuations in the cathodic protection potential under the impact of stray currents lead to the occurrence of local corrosion on steel structures operated in soils and seawater. The potential fluctuations induced by both alternating and direct current sources can be simulated by cycling a square potential step. This paper covers the impact of sign-alternating cyclic polarization (SACP) on the general and local corrosion of carbon steel in 3.5% NaCl solution containing a borate buffer (pH 6.7) and without it. A decrease in the cathodic half-period potential (Ec) of SACP inhibited the general corrosion and accelerates the local corrosion of steel in both solutions, which was associated with an increase in the amount of hydrogen in the metal. Increasing the duration of the SACP cathodic half-period increased the pit density and total area at less negative Ec values. At more negative Ec values, an increase in the duration of cathodic polarization reduced the intensity of steel local corrosion in the unbuffered chloride solution. This effect is explained by blocking of the pit nucleation centers on the metal surface by a layer of steel dissolution products formed in the near-electrode electrolyte layer with a high pH. The combined body of data shows that hydrogen absorption by the metal determines the corrosion behavior of carbon steel under the impact of SACP in chloride solutions, which should be taken into account in the development of models of the corrosion of steel structures under the action of stray currents.

Three-Dimensional Morphology and Watershed-Algorithm-Based Method for Pitting Corrosion Evaluation

Pitting corrosion and stress concentration at rust pits are the principal reasons for severe degradation in fatigue performance of corroded steel structures. The accurate evaluation of rust pits on rough and uneven corrosion surfaces is the foundation of fatigue life estimation for corroded steel structures. In this paper, a new method for the identification, extraction, and evaluation of rust pits on the surface of corroded steel structures was proposed based on a three-dimensional morphology and watershed algorithm. An accelerated corrosion experiment was first executed to acquire corroded steel plates, and then surface profile measurements were conducted to obtain the three-dimensional morphology of the corroded steel surfaces. Furthermore, the surface topography data of the corroded steel surfaces were written into a gray matrix through coordinate transformation. Then, the gray matrix was successively filtered and gradient-mapped, and the watershed was calculated to obtain the pit mark matrix and pit depth matrix. A calculation method for the size and shape of rust pits was consequently developed, and a statistical analysis of the extraction results of the rust pits was also conducted. The results showed that rust pit density had a peak value at the corrosion duration of 3 months, and rust pit density showed a fluctuating process with corrosion duration that continued to increase until 15 months. The values of the depth diameter ratios of rust pits were concentrated in the range of 0.1~0.8. With corrosion duration increasing from 3 months to 4, 6, 8, 12, and 15 months, the distribution range of the depth diameter ratios of rust pits decreased at first and then increased, followed by decrease and, finally, increase. The width distribution of the rust pits was independent of the depth distribution of the rust pits. The values of the volume ratios were mostly distributed between π/12 and π/4, and the shapes of most rust pits were similar to half (ellipsoidal) spheres.

A Modeling Method for Finite Element Analysis of Corroded Steel Structures with Random Pitting Damage

Aiming at simulating the surface morphology of corroded steel and providing a modeling method with higher accuracy, the accelerated corrosion test was used to obtain six groups of corroded specimens, and then applied to stochastic finite element analysis (FEA) for studying the mechanical behavior of corroded steel. The pitting parameters (the depth, width, and diameter–depth ratio) of all specimens were investigated and statistically analyzed. Considering the irregularity of corroded surface, the random pitting model (RPM) was established based on the secondary development of ABAQUS. Moreover, the rough surface meshing method (RSMM) was subsequently proposed to optimize the element quality of the FEA model. At last, the modeling method was applied to investigate the bearing capacity of corroded steel beams. The results indicate that, firstly, the pitting parameters of all specimens obeyed log-normal distribution, and their logarithmic mean values grew with increase in corrosion time. The corroded surface the RPM can reproduce the evolution behaviors of a corroded surface with higher accuracy. In addition, the FEA model of corroded steel structures can be meshed easily into hexahedron elements by using the RSMM and effectively optimizing the number and quality of elements. By comparing with other test results, the calculation results of the FEA model of steel beams established by using the modeling method proposed in this study demonstrate a good accuracy in mechanical behavior analysis. The modeling method provides further support for the study of mechanical properties of corroded steel structures.

Experimental investigation on corrosion of structural steels in molten Pb-Mg and LBE

• A comparative investigation on two F/M steels and two austenitic steels exposed to LBE and Pb 83 Mg 17 was conducted. • High temperature Pb-Mg results in slight dissolution corrosion in F/M steels and strong dissolution corrosion in austenitic steels. High temperature LBE causes oxidation in all structural steels. • Pb-Mg should be carefully considered if it will be deployed in future LFRs. Lead and its alloys are commonly used as coolant and liquid spallation neutron targets for advanced nuclear reactors and ADS systems. Pb-Mg alloy may be a potential coolant and maintain an acceptable corrosion rate without additional oxygen control in comparison with LBE. A comparative study on corrosion behavior of two F/M steels (SIMP, T91) and two austenitic steels (316L, 15-15Ti) in liquid Pb-Mg and LBE at 550°C for 1000h has been studied in this work. In Pb-Mg, F/M steels show slight dissolution corrosion and austenitic steels show severe dissolution corrosion. In LBE, all steels form oxide layers and a three-layer structure is observed in F/M steels.

Laser cleaning on severely corroded steel members: Engineering attempt and cleanliness assessment

A highly effective, environmentally friendly, high-power continuous-wave laser (CWL) transmitter was newly developed to remove corrosion products from severely corroded steel structures. In this regard, treatment conditions of dry laser cleaning (DLC) and wet laser cleaning (WLC) of the drench, soak, and rinse methods are adopted, and the cleanliness effect is compared with that of conventional abrasive blasting treatment. The morphologies and chemical compositions of untreated and treated surfaces are analyzed using three-dimensional digital microscopy, laser confocal microscopy, and scanning electron microscopy–energy dispersive X-ray spectrometry. The results show that laser cleaning can efficiently remove corrosion products and salts that severely corrode steel members, as well as prolong the re-corrosion time of the cleaned surfaces. WLC can achieve excellent microscopic cleaning and reduce the effect of high-temperature inputs on the surface via laser irradiation. Further mechanistic analysis indicates that ablation, melting, and evaporation during laser cleaning primarily contribute to the removal of corrosion products and salts. As a result, the WLC drench method yields the best surface cleanliness and is suitable for practical engineering applications. This study provides a basis for maintaining severely corroded structures via laser-cleaning techniques.

Bond behavior between CFRP and corroded steel plate associations with surface treatments

This study focused on the interfacial bond behavior of steel-CFRP (carbon fiber-reinforced polymer) adhesion joint associations with different steel surface treatments through typical pull-off and shear tests. The specimens were fabricated based on wet layup laminating CFRP and clean/corroded steel plates. Four types of surface treatments and two kinds of pre-coating processes were investigated to optimize the interfacial bond behavior. Meanwhile, the conventional rust removal methods were also studied by clarifying the physical and chemical characteristics of steel surfaces. Test results evaluated the topography, microstructure, and surface composition of clean and corroded steel specimens, and qualitatively established their relation to bonding behaviors and failure modes. A strong correlation existed between the surface geometry properties and the tensile/shear strength, however, for clean and corroded steel surfaces their fracture mechanisms differ. Various physical property parameters of the corroded surface related to surface treatment will further affect the bond performance. The corresponding adhesion mechanisms were mathematically demonstrated based on the surface energy principle. The present experimental results provide new insights into the interfacial bond mechanism between corroded steel structures and adhesive or CFRP composites.