Corrosion Specimens Research Articles

Corrosion of Low Carbon Steel in Chloride Containing Environment

This research aims to investigate the corrosion of low-carbon steel in a chloride-containing environment. The investigation started by preparing and studying the surface condition of the specimens. The mechanical properties, microstructures and chemical compositions were also comparatively investigated between standard and corroded specimens. The results showed that the surface of the corroded samples was rough and peeling, different from the standard specimens, which were relatively smooth and non-corrosive. The average ultimate tensile strength and average yield strength of normal specimens were higher than those of corroded specimens at 5.39% and 2.32%, respectively. The corrosion products developed on the surface of corroded specimens caused a high-stress concentration area. The specimen is more prone to cracks and breaks when subjected to tensile stress. The surface of the normal specimen was composed of iron, oxygen, carbon, and silicon. In contrast, the surface of the corroded specimen contained the same elements as the normal specimen except chlorine which was detected. The film layer of the corroded specimen was cracked in contrast with the normal specimen, where the film still covered the metal substrate. The chemical composition analysis found that the corroded specimen's film layer contained chlorine, which is not detected in the film layer of the normal specimen. This is because the film layer of hot-rolled steel remains porous even passing the hot-rolling process. These pores allow chloride ions to diffuse and react with the film layer and the metal substrate. This makes the film layer of the corroded specimen thicker and initiates cracks. When stable alpha-iron-oxyhydroxide is formed on the steel surface, it can help to suppress corrosion.

Seismic performance of earthquake-damaged corroded reinforced concrete beam-column joints retrofitted with basalt fiber-reinforced polymer sheets

This present research conducted an experimental study on the influence of different earthquake damages on the seismic performances of aged reinforced concrete (RC) beam-column joints retrofitted with basalt fiber-reinforced polymer (BFRP) sheets under cyclic loadings. Six beam-column joints included one benchmark specimen, one uncorroded specimen retrofitted with BFRP sheets, and four earthquake-damaged corroded specimens with the corrosion rates of 0% and 9% retrofitted with BFRP sheets. Test results demonstrated that the seismic performances of earthquake-damaged corroded specimens effectually improved after retrofitting with BFRP sheets, and the retrofitting effectiveness was significantly affected by the earthquake-damaged levels. The bucking of stirrups, spalling and crushing of concrete of retrofitted specimens were effectually postponed, while the ductility of corroded and uncorroded specimens under the earthquake damages increased after retrofitting with BFRP sheets. The total cumulative energy dissipation and final stiffness of retrofitted specimens considerably improved with the maximum increase of 22.3% and 14.3% comparing to those of benchmark specimen, respectively. Besides, the models for predicting the shear strength of RC beam-column joint cores considering the influences of earthquake damage, reinforcement corrosion, and FRP retrofitting were proposed.

Degradation of bond strength and deformation between TRC-confined seawater sand concrete and BFRP bars under chloride corrosion environment

The interfacial bonding performance between seawater sand concrete and basalt fiber reinforced polymer (BFRP) bars were tested under different textile reinforced concrete (TRC) confinement layers, confinement sequences and chloride salt dry-wet cycles. The results show that TRC confinement can change the failure mode of the specimen and improve the ductility of specimens. With the increase of corrosion age, compared with the specimens with the same restrained layers in the conventional environment, the ultimate bond strength of restrained specimens before corrosion gradually decreases, and the slip value when reaching the ultimate bond strength also slightly decreases. The bond strength of the pre-restrained corroded specimens has the same development trend. Based on the bond-slip model of deformed steel bars and concrete proposed by Eligehansen for the first time in 1983—BPE model, under the control of TRC confinement and corrosion age, the relationship between the TRC confinement layer and the ultimate bond strength and slip of seawater sand concrete and BFRP steel bar is established. By fitting and predicting the ultimate bond strength, corresponding slip value, and corrosion age control of different TRC confinement layers, it is found that the confinement effect will not be significantly improved when the confinement layers exceed 4 layers. Under long-term chloride corrosion, the failure mode of the specimen may still change into splitting failure when the number of restrained layers is small.

Study of Temperature on the Corrosion Behavior of Antibacterial Steel by a Large-Scale Multiphase Flow Corrosion Test Loop.

The System #2 flow loop used in this study is a 4-inch-diameter, high-temperature, high-pressure system. In situ corrosion and electrochemical measurements were performed using a homemade flat corrosion specimen and a three-electrode probe. The experiment results show that temperature has an accelerated influence on the corrosion of antibacterial alloy steel. With the increase of temperature and the presence of O2 in the environment, a loose and porous corrosion product film was formed on the surface of the resistant steel, which made it easier for the corrosion medium to enter the corrosion product film from the pore, thus accelerating the corrosion.

Experimental and numerical analysis of ratcheting behavior of A234 WPB steel elbow joints including corrosion defects

In this paper, ratcheting behavior of intact and corroded 90o elbow pipe specimens of A234 WPB steel is investigated at intrados, crown, and extrados positions. A special fixture was designed and constructed to carry out the fatigue experiments. Then, the effects of fatigue loading parameters (mean and amplitude) and defect depth were examined on ratcheting responses of intact and corroded specimens at intrados, crown, and extrados positions. To simulate the ratcheting behavior of specimens, a finite element analysis was performed based on the combined nonlinear isotropic/kinematic hardening model. As a reasonable agreement was found between the finite element (FE) simulation results and experimental data, the influence of constant internal pressure during the cyclic loading was examined on ratcheting responses through FE simulation. Results indicated that decreasing the load amplitude was more effective on decreasing the ratcheting strain than that of the mean fatigue load. Moreover, the most critical ratcheting response was associated with the intrados location of the pipe. For defective specimens, decreasing fatigue loading parameters resulted in a shakedown behavior for a defect placed at extrados, while, for the defects at intrados and crown, an increasing behavior was observed for the ratcheting strain. It was revealed that, at extrados position, the ratcheting behavior was arrested up to 1 mm defect depth. The ratcheting strains were increased at intrados and crown by increasing the internal pressure, while they were decreased at extrados.

Corrosion effect on structural behaviour of bolted steel connections under axial tension loads

Corrosion is one of the most important problems and is an inevitable event in metal structures exposed to environmental effects. Corrosion deterioration usually forms in steel and steel-concrete composite bridges and marine structures. Bolted connections in steel structures are the preferred connection types because of their ease of assembly and high strength. In this study, corrosion damages were created in steel plates with bolted connections and the axial load strength, ductility and behaviour of the steel members were investigated. Axial tensile tests have been carried out on steel plates with bolted connections exposed to corrosion at different rates (10% and 20% by mass). According to the axial tensile tests, decreases in average yield strength and average yield strain values were determined as 4% and 10% for 10% corroded specimens, and were determined as 16% and 27% for 20% corroded specimens having 4 mm thick plates, respectively. Similarly, for specimens having a thickness of 6 mm plate, average yield strength and average yield strain values decreased 3% and 5% for 10% corroded specimens, and 13% and 14% for 20% corroded specimens, respectively. Also, it was found that the ultimate strengths and average rupture strains decreased almost proportionally to the amount of corrosion. In addition, finite element analysis was performed in ANSYS program for bolted connections examined experimentally. In terms of ultimate tensile strength, the results were obtained with an average error of 4% in non-corroded 4 mm specimens and 6% in 10% and 20% corroded 4 mm specimens. For 6 mm plate thickness, these values of non-corroded, 10% and 20% corroded specimens were obtained as 9%, 5% and 3%, respectively.

Fractal characteristic of corroded steel surface and application to the fracture analyses

To analyze the effects of morphological characteristics on fracture behaviors of corroded steel, the morphology analysis, tensile test and corresponding finite element (FE) simulation were systematically performed to investigate the morphological evolution and the degradation of mechanical property of corroded steel. The results indicated that the size parameters (C and W) followed the Chi-square distribution, and the fractal character was obviously observed on corroded steel, especially for critical corrosion pit. The fractal dimension of critical corrosion pit (D*) was a key factor influencing the mechanical property and fracture behavior for corroded steel due to the advantage in systematacially reflecting the morphological characteristics, the agreement with the various mechanical parameters was obvious more than C or W of critical corrosion pit. Comparing the toughness parameters (α and η) among different corroded specimens, the effect of the oxide passivation layer on fracture toughness properties of corroded steel was revealed, and modified. Finally, the characterization of D* on fracture toughness parameters (α, η, effective plastic strain εpcritical and stress triaxiality T) of corroded steel was discussed

Rehabilitation of seismic-damaged reinforced concrete beam-column joints with different corrosion rates using basalt fiber-reinforced polymer sheets

Reinforcement corrosion and seismic damage considerably affect the seismic performance of reinforced concrete (RC) members. In present research, five RC beam-column joints were designed and tested under cyclic loadings. These joints included one reference specimen, one uncorroded specimen rehabilitated with basalt fiber-reinforced polymer (BFRP) sheets, as well as three seismic-damaged corroded specimens with corrosion rates of 0, 3%, and 9% rehabilitated with BFRP sheets. The seismic behavior of tested specimens, involving the hysteretic responses, ductility, and energy dissipation was discussed. Test results demonstrated that the seismic behaviors of seismic-damaged corroded specimens were effectually upgraded after being rehabilitated with BFRP sheets. The spalling and crushing of concrete, as well as the buckling of stirrups were postponed by the utilization of BFRP sheets, while ductile behaviors of rehabilitated specimens could be observed in the test. Besides, the ultimate displacements, final stiffness, and total cumulative energy dissipation of the rehabilitated specimens were considerably improved with the maximum increase of 14.9%, 16.7%, and 23.3%, respectively. Equations considering the influences of reinforcement corrosion, seismic damage, and FRP rehabilitation on the shear strength of the core area of RC joints rehabilitated with FRP sheets were proposed, and good agreements could be found between the theoretical and experimental results.

A machine learning approach for predicting the electro-mechanical impedance data of blended RC structures subjected to chloride laden environment

The application of the electro-mechanical impedance (EMI) technique using piezo sensors for structural health monitoring (SHM) is based on baseline/healthy signature data, which poses serious limitations when it needs to be applied to existing structures. Therefore, the present research utilizes autoregressive integrated moving average (ARIMA), an effective time series forecasting machine learning algorithm to predict the baseline/healthy EMI data and futuristic data of reinforced concrete corroded specimens. The EMI data from the ARIMA model is validated with the experimental data, and the results obtained prove that the model could be utilized to predict the baseline and forecast the EMI corrosion data effectively. These results will aid the researchers to predict the baseline data for the existing structures and utilize the EMI technique for SHM purposes.

Effect of current density on the cathodic protection efficiency and mechanical properties of pre-stressed high-strength steel wires for stay cable

Stay cables are the main force-bearing structures of cable-stayed bridges, which are mainly composed of internal high-strength steel wires and external high-density polyethylene (HDPE) sheaths. When the external HDPE sheaths crack, the internal high-strength steel wires are severely corroded, thereby endangering the security of the whole bridge. The effects of pre-stress level and protection current density on the cathodic protection efficiency and mechanical properties of stay cable high-strength steel wires were investigated in this study on the basis of the impressed current cathodic protection (ICCP) method for stay cable high-strength steel wires in rainwater environment. The corrosion degree of steel wires was characterized qualitatively and quantitatively by observing the macro and micro morphologies of the corrosion specimen and the weight loss measurement. The ICCP efficiency was evaluated in terms of the variation of open circuit potential (OCP) and instant-off potential (IOP). Static tensile test was used to investigate the difference in the mechanical properties of steel wires with different corrosion degrees. Results showed that the corrosion rate of steel wires increased with pre-stress level, and the greater the pre-stress, the higher the corrosion probability of steel wires. The application of ICCP reduced the accumulation of rust on the surface of the steel wires and the number and size of corrosion pits. The ICCP efficiency increased with the protection current density. No significant difference was found in the IOP values of the steel wires with different pre-stress levels when the protection current density was constant. All the steel wires with ICCP in the later stage of the test were effectively protected and are not in the overprotected state.

August Rauber’s ideas for the creation of an Anatomy Museum in Lithuania (1920–1940)

Professor August Rauber (1841–1917) created the most important school of anatomy in the Baltic region. His students continued his educational and research work in their native countries. One of them was Professor Jurgis Žilinskas (1885–1957) who laid the foundation to Lithuanian anatomy and anthropology. From 1906–1912, he studied medicine at the University of Yuryev (Tartu) where Prof. A. Rauber worked for 25 years as Head of the Institute of Anatomy. In 1890, A. Rauber opened the Anatomy Museum there. In the university, J. Žilinskas maintained close contacts with Professors A. Rauber (1841–1917), N. N. Burdenko (1876–1946), W. Zoege-Manteuffel (1857–1926) and E. Landau (1878–1959). After graduation from the university, J. Žilinskas as a talented student was invited to work as an assistant at the Department of Hospital Surgery at Yuryev University. After Lithuania restored its independence on 16 February 1918, Prof. J. Žilinskas participated actively in the organization of medical studies in Lithuania (1922–1940) and was one of the creators and the principal patron of the Museum of Anatomy. Returning to Lithuania, J. Žilinskas brought along the most advanced ideas of his professors, especially of his honoured Prof. A. Rauber. During this period, the collection of the museum increased to 3,890 specimens. Osteological specimens comprised 1,925 (around 50%) of the specimens, wet specimens – 753 (19.3%), corrosion specimens – 467 (12%), transparent specimens – 201 (5.2%), dry specimens – 107 (2.8%) and models – 437. Professor J. Žilinskas’ collection constitutes 50% of the present exhibits at the Anatomy Museum of the Lithuanian University of Health Sciences.

Corrosion Resistance of a Plasma-Oxidized Ti6Al4V Alloy for Dental Applications

A Ti6Al4V alloy was plasma-oxidized at 600 °C during 1, 2, 3, 5 and 8 h and corroded in an artificial saliva solution. Electrochemical evaluation was performed by using potentiodynamic polarization curves, linear polarization resistance (LPR), and electrochemical impedance spectroscopy (EIS) measurements during 100 h. Corroded specimens were characterized by using Raman spectroscopy and scanning electronic microscopy (SEM). All tests indicated that the highest corrosion resistance was obtained for specimen oxidized during 3 h since the noblest free corrosion potential, lowest passive and corrosion current density values, as well as the highest polarization resistance values were obtained under these circumstances. EIS measurements indicated that the highest impedance and phase angle values obtained for this specimen exhibited a high capacitive behavior typical of a very compact passive film.

Mechanical behavior of locally corroded circular steel tube under compression

Localized corrosion often occurs on steel members due to paint peeling led from insufficient durability of the coating material or human collision, which may significantly reduce the load carrying capacity and safety performance of the structures. The effects of the parameters such as localized corrosion penetration, circumferential corrosion ratio, longitudinal corrosion ratio, slenderness ratio and eccentricity of mechanical behaviors of locally corroded circular steel tubes under compression were studied experimentally and numerically. Based on the test results and the finite element analysis, a calculation method was proposed for predicting load carrying capacity of the corroded specimen under compression. It is found that localized corrosion did not change the failure modes of test specimens, and all of them failed in the limit point buckling mode. The factors affecting the degradation of load carrying capacity and stiffness of localized corrosion specimens from high to low were corrosion time, circumferential corrosion ratio and longitudinal corrosion ratio. The most unfavorable localized corrosion modes of load carrying capacity and stiffness were H3L3-270 and H3L1-270, respectively. The load carrying capacity degradation of members increases with the increase of the localized corrosion ratio, circumferential corrosion ratio and longitudinal corrosion ratio, while decreases with the increase of the eccentricity. The formula proposed can be used to predict the load carrying capacity of locally corroded circular steel tube members under compression.

Corrosion behavior of boronized nickel-based alloys in the molten chloride Salt

The study investigates the effects of diffusion coating by boronization on the corrosion behavior of IN718 and C276 in molten KCl-MgCl2-NaCl salt at 800 °C. The boride layer was uniform and non-porous comprising of an outermost (nickel-silicide and metal-borides) layer, the middle "compound" (metal-borides), and inner "dispersed" or "diffusion" layer (intermixture of metal-borides). Both the boronized alloys exhibited better corrosion resistance. The average mass-loss (mg/cm2) was in the increasing order of boronized C276 < boronized IN718 < C276 < IN718. The non-boronized corrosion specimens indicated localized corrosion (pitting) and selective Cr depletion, while the boronized corrosion specimens showed the boride layer was intact and strongly adhered to the surface with no significant changes in its microstructure.

Inhibition efficiency of pyrazinecarboxylic acid on mild steel in acidic environment

Pyrazinecarboxylic acid (PCA) was examined as a potential corrosion inhibitor for mild steel (MS) in 0.5 M HCl environment. The methods of electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR), as well potentiodynamic (PD) polarization were utilized. Furthermore, atomic force microscopy (AFM) and quantum chemical calculations were utilized. PD polarization curves demonstrated that PCA exhibited mixed inhibitor behavior. Scanning electron microscopy (SEM) offered the creation of an adsorptive layer on the surface of MS which prevented the steel against corrosive specimens. Furthermore, density functional theory (DFT) presented good agreement with electrochemical experimental results. The adsorption equilibrium constant () value was calculated to be 3.704 × 104 M −1 which was related to a high proportion of inhibitor on the surface. In the presence of 1.0 mM PCA, inhibition efficiency was determined as 95.2% from EIS results.

Bending performance of connection-corroded welded hollow spherical joints

Indoor swimming pools are a typical aggressive environment in which long-span steel structures are prone to corrosion, especially in the connection position of joints. In order to evaluate the impact of the corrosion on the mechanical properties of joints, a corrosion test of Q235 steel in a swimming pool environment was carried out for 48 and 72 months respectively. The surface pitting distribution of the corrosion specimens was measured and statistically analyzed, and a probability distribution model of surface pit depth was established. Then, a finite element model of welded hollow spherical joint, which could simulate local corrosion and pit distribution, was established, and the parameter analysis of connection-corroded joints on bending performance was conducted. The results demonstrated that the hoop corrosion range and corrosion depth rate were the most sensitive parameters to the bending performance. Taking the number of hoop corrosion zones and corrosion depth rate as parameters, the bending bearing capacity degradation rates of connection-corroded joints based on a specific guarantee rate and different conditions were obtained. Finally, a convenient method for evaluating the joints' bending bearing capacity degradation rate was proposed, which could provide a reference for studying the mechanical properties of similar connection-corroded joints and evaluating the safety performance of grid structures.

Hysteretic behavior and cyclic constitutive model of corroded structural steel under general atmospheric environment

To study the hysteretic behavior of corroded steel under cyclic loading, corrosion morphology tests, monotonic tensile tests and cyclic loading tests were conducted on 7 groups of accelerated corrosion specimens and 10 groups of natural corrosion specimens. A new corrosion damage parameter Dn for corrosion degree evaluation and mechanical properties prediction and an extracting method based on corrosion morphology were proposed. It was found that corrosion reduced the strength, ductility and hysteretic energy of steel, and the degradation law of monotonic/hysteretic performance with corrosion damage parameter Dn was obtained. By analyzing the degradation laws of material parameters in classical combined hardening model with the corrosion degree and studying the relationship between the material parameters in monotonic and cyclic loading conditions, a plastic constitutive model of corroded steel was established. The simulated stress-strain curves of corroded steel were in good agreement with the experimental data, indicating that the proposed model successfully simulated the monotonic/cyclic loading performance of corroded steel.

Axial Compressive Performance of Corroded Concrete Columns Strengthened by Alkali-Activated Slag Ferrocement Jackets

Chloride-induced corrosion of reinforcement has endangered the safety of reinforced concrete (RC) structures. It is, therefore, necessary to strengthen the corroded RC members to ensure structural safety. This study aims to investigate the effectiveness of alkali-activated slag (AAS) ferrocement jackets in strengthening corroded RC columns. AAS ferrocement specimens with various layers of stainless steel wire mesh (SSWM) were subjected to direct tensile tests. Square RC columns suffered artificially accelerated corrosion and were subsequently strengthened by AAS ferrocement jackets. Axial compressive tests were conducted on the column specimens. Experimental results have shown that corroded specimens suffer severe losses in loading capacity up to 46% as compared with the control one. Volume fraction of transverse SSWM (ρv) plays primary role in loading capacity and ductility of ferrocement and its confinement on column specimens. Ferrocement with ρv of 0.266% can rehabilitate loading capacity of specimens with corrosion degrees of 8.9% and 18.3% by 37% and 46%, respectively. Corroded specimen strengthened by ferrocement with ρv of 0.532% achieves approximately two times the ductility than the one without strengthening. Ferrocement jackets provide better and uniform confinement to core concrete than new stirrups. Analytical models are proposed to predict tensile strength of AAS ferrocement and loading capacity of specimens strengthened by ferrocement jackets. The prediction is in good agreement with experimental results.

Bond degradation of non-uniformly corroded steel rebars in concrete

In this work, the bond degradation of non-uniformly corroded steel rebars embedded in concrete was studied. A total of 105 concrete specimens with accelerated corrosion of steel rebar were evaluated using the pull-out test. The influences of corrosion mode, corrosion level, orientation of the longitudinal rib, and the position of steel rebar on the bond degradation were analyzed. The cracking patterns of corrosion-induced cracks, bond failure modes, and bond stress-slip relations were discussed. The results showed that the orientation of longitudinal rib and the thickness of concrete cover play a vital role in determining the cracking patterns of corrosion-induced cracks. In comparison to the uniformly corroded specimens, the bond performance of specimens with non-uniform corrosion of steel rebar degraded more significantly, and this phenomenon became even more pronounced as the corrosion level increased. Moreover, the beneficial improvements caused by the expansive rust on the bond performance were greatly dependent on the degrees of concrete constraint and corrosion level.

Influence of the transient conditions on release of corrosion products and oxidation of alloy 690 tubes during pressurized water reactor restart after steam generators replacement

The radioactivity of the Reactor Coolant System (RCS) of Pressurized Water Reactors (PWRs) mainly comes from the release of corrosion products of Steam Generator (SG) tubes made of Ni-base alloys. In order to reduce this activity and thus the radiation exposure of PWR operators during maintenance operations, it is necessary to minimize the release. That requires prior understanding of the various mechanisms involved. EDF R&D constructed a loop, BOREAL, to specifically measure rates of release of SG tubes in various conditions of primary environment. Tubes were usually tested at high temperature, under constant conditions of primary chemistry. So, it is necessary to carefully investigate the impact of transient conditions during a PWR restart after SG replacement. Tests were performed on the industrial material with curvature, roughness, defects and heterogeneities, regularly observed on this type of component. Characterisations of the inner surface were done on as-received and corroded specimens of SG tubes and were correlated with the obtained release kinetics.The native oxide layer is formed of a very thin layer (1-2 nm) of oxidised matrix, without specific enrichment. During the restart, the most critical step for the release phenomenon is revealed from 170°C to 297°C. The majority of the metal is indeed released into the fluid during this step. The characterisations after release tests have made it possible to propose oxidation and release mechanism during a PWR restart after SG replacement. Up to 170°C, a thin layer of amorphous chromium oxide is formed by selective dissolution of iron and nickel. When the temperature rises, this chromium oxide layer is not stable enough to be protective and the diffusion phenomena are activated. At 325°C, the oxide does not exhibit any particular enrichment and corresponds to an oxidised metal layer; an equilibrium is established and the rate of release reaches a pseudo-stationary regime.