Effect Of Corrosion Research Articles

Experimental study on the behavior of small-scaled circular and square RC columns under various loading conditions and corrosion effect

Reinforced concrete columns are vital load-bearing elements, responsible for transferring vertical loads and resisting lateral forces. While numerous factors govern column performance, this study pinpoints cross-sectional shape, transverse reinforcement configuration, and the corrosive threat as its primary areas of investigation. Thus, 20 small-scaled (1/8th scale) RC columns (square and circular, with ties or spirals) were tested under various loading conditions. Columns were divided into five groups. A preliminary test was conducted to determine individual axial load capacity through failure under axial compressive loading. The main test then explored their behavior under combined axial load and variable lateral drift compared to their behavior at two corrosion levels 15% and 25%. While corrosion levels were roughly achieved, uneven distribution due to the accelerated process concentrated pitting near construction joints, impacting reinforcement more than rebar. Results confirmed the efficacy of spirals in enhancing capacity, particularly for circular columns where they also increased lateral load capacity. However, spirals also amplified corrosion vulnerability in circular columns, suggesting a steeper decline in performance at higher corrosion levels. Two key models were derived from analyzing the recorded data: normalized total dissipated energy and normalized absolute peak load. Future research should prioritize exploring column behavior under a wider range of combined loads and corrosion levels to refine and validate these models.

Effect of corrosion on mode I fracture toughness and fracture behavior in A7075/CFRP adhesive bonded joints

The interlaminar fracture toughness of aluminum alloy/carbon fiber reinforced plastic (CFRP) joints subjected to accelerated aging due to corrosion was investigated over time. An acoustic emission (AE) measurement was performed as an evaluation method in conjunction with double cantilever beam testing. It was confirmed that the difference in the number of cross-linking points in the adhesive affected the fracture morphology and corrosion behavior, which resulted in a change in the fracture toughness. The AE measurements facilitated the visualization of the process zone and real-time monitoring of the fracture morphology, and they were able to capture changes in the fracture behavior with the corrosion progression.

Fire performance of aged and corroded reinforced concrete columns

The existing guidelines for determining the fire ratings of reinforced concrete (RC) columns only take into account undamaged components, without considering any deterioration caused by age or corrosion. An experimental study was conducted to examine the effect of corrosion on the fire performance of RC columns. In this study, six full-scale RC column specimens were cast, corroded, and tested in fire conditions, consisting of two made of normal strength concrete (NSC) and four made of high-strength concrete (HSC). Out of these six, three RC columns (1-NSC and 2-HSC) were corroded using a specifically designed accelerated corrosion setup for a target mass loss of 30 %. After the completion of the accelerated corrosion exposure time, these three corroded column specimens, along with three other non-corroded control column specimens, were tested in a fire furnace, simulating the ISO-834 fire curve. It was found that due to corrosion exposure, the steel reinforcement underwent significant mass loss, and severe corrosion cracks were observed. These cracks were discovered to serve as convenient channels for heat transfer. This facilitated the earlier and more severe spalling of the concrete cover, ultimately leading to premature deterioration in the strength of the corroded RC columns during the fire. Consequently, this contributed to the catastrophic failure of the corroded RC columns, with a significant reduction in fire ratings- 44 % for NSC columns and 40.49 % for HSC columns. This paper also addresses the spalling characteristics of the corroded columns and their structural responses, including axial deformations, lateral deformations, and load variations.

Framework for lifecycle resilience assessment of earthquake-damaged coastal RC structures considering non-uniform corrosion

Reinforced concrete (RC) structures in seismic coastal areas often suffer from the coupled effects of corrosion and earthquakes due to prolonged exposure to harsh environmental conditions. Previous research on the seismic performance of buildings primarily focused on uniform corrosion(UC), disregarding the impact of varying concentrations of chloride-ions on corrosion rate. This discrepancy will overestimate the seismic performance of building structures. The framework proposed in this study aims to evaluate the resilience of RC structures to non-uniform story corrosion(NUSC). The framework encompasses an innovative functional recovery function and considers the influence of chloride-ions concentration on the corrosion rate, time-varying initial functional function, and degradation model for corroded reinforced concrete. NUSC model is established within the proposed framework via OpenSees software. The proposed framework integrates the seismic hazard, fragility, resilience, and recovery models. A nonlinear time history analysis method is employed to simulate the structural response to the seismic action. The findings demonstrate that NUSC leads to a reduction in seismic resilience by 7.3% and 10% compared to UC when considering service times of 35 and 55 years, respectively. This indicates an escalation in seismic risk as well as a decline in structural seismic capacity.

Revolutionizing multifunctional electrolyte additive design and synthesis for high-voltage nickel-rich batteries in diverse climates

The high-voltage LiNi0.6Co0.2Mn0.2O2 (NCM622) cathode presents a promising avenue for advancing the energy density of lithium-ion batteries. Nevertheless, current limitations primarily arise from electrolyte systems unable to meet stringent criteria, including stable performance under elevated temperatures and efficient discharge at low temperatures. In this study, we address these challenges by designing a molecular structure incorporating boron oxygen functional groups, phenyl-, and fluorine moieties to simultaneously enhance ion conductivity and thermal stability under extreme voltages. A multifunctional electrolyte additive, 3, 4, 5-trifluorophenylboronic anhydride (TFPBA), has been successfully developed via synthesis. TFPBA plays a pivotal role in promoting the formation of a hierarchical cathode electrolyte interphase (CEI) through its preferential decomposition and oxidation processes. This CEI features a mechanically stable inner layer enriched with fluorophenyl- groups, crucial for high-temperature cycling, alongside an outer layer concentrated with BxOyFz complexes that significantly improve Li+ conductivity, ensuring superior performance under low-temperature conditions and at elevated rates. Moreover, TFPBA acts as an HF scavenger within the electrolyte, mitigating corrosive effects on the cathode surface, thereby curtailing CEI reformation and the transition metal dissolution. The Li/NCM622 half cells with TFPBA exhibit impressive capacity retention rates of 92.58%, 80.09%, and 81.77% after extensive cycling at temperatures of −20 °C, 25 °C, and 55 °C, respectively. Moreover, NCM622/graphite full cells with TFPBA achieve a remarkable capacity retention of 97.97% after 150 cycles at room temperature. Our findings highlight the exceptional electrochemical performance of NCM622 cathodes at elevated voltages across a wide temperature range, providing valuable insights for the development of advanced electrolytes in high-demand applications.

A device for dynamic testing of the refractory ceramic resistance to biomass ash

The corrosive effects of biomass ash on refractory materials in combustion chambers pose challenges. Development of new castable refractory materials which are more resistant to corrosion requires tests that accurately reflect the conditions occurring in real devices. This article describes the Computational Fluid Dynamics (CFD) design and construction of a device for evaluating the corrosion of refractory materials in dynamic regime. The device allows to simulate combustion chamber conditions accurately, to regulate an injection of corrosive medium on the tested material surface under the specified conditions (temperature, time, and flow). In the present investigation the conventional refractory material was exposed to attack of biomass ash at the temperature of 1300 °C for 3 h to test the functionality of the device. A burner with technology oxygen–enriched combustion was used to heat the device. The corrosion tests were conducted in accordance with the standard P CEN/TS 15,418 and the standard STN EN ISO 21404. The operational state required for corrosion tests at 1300 °C was achieved within 1.12 h. The extent of refractory material degradation in the dynamic corrosion regime was evaluated using electron microscopy-energy dispersive spectroscopy (EM-EDS) and compared with the results of a static crucible test (3 h at 1300 °C). The dynamic test provided sufficient information on the interactions of corrosion medium with the refractories. Its main advantages are the maintenance of non-equilibrium conditions by controlled deposition of the corrosion medium in quantity from 1 to −100 g/h, fast heating rate to operating temperature (20 °C/min), and the possibility of conditions variability during tests (temperature, ox-red. atmosphere, fuel gas flow etc.).

Naphthenic Acid Corrosion Mitigation: The Role of Niobium in Low-Carbon Steel.

Naphthenic acid corrosion is a well-recognized factor contributing to corrosion in the construction of offshore industry pipelines. To mitigate the corrosive effects, minor quantities of alloying elements are introduced into the steel. This research specifically explores the corrosion effects arising from immersing low-carbon steel, specifically A333 Grade 6, in a naphthenic acid solution. Various weight percentages of niobium were incorporated, and the resulting properties were observed. It was noted that the addition of 2% niobium in low-carbon steel exhibited the least mass loss and a lower corrosion rate after a 12 h immersion in naphthenic acid. Microstructural analysis using scanning electron microscopy (SEM) revealed small white particles, indicating the presence of oil sediment residue, along with corrosion pits. Following the addition of 2% niobium, the occurrence of corrosion pits markedly decreased, and only minor voids were observed. Additionally, the chemical composition analysis using energy-dispersive X-Ray analysis (EDX) showed that the black spot exhibited the highest percentage of carbon, resembling high corrosion attack. Meanwhile, the whitish regions with low carbon content indicated the lowest corrosion attack. The results demonstrated that the addition of 2% niobium yielded optimal properties for justifying corrosion effects. Therefore, low-carbon steel with a 2% niobium addition can be regarded as a superior corrosion-resistant material for offshore platform pipeline applications.

Combined effects of corrosion and fire on load-carrying response of hot-rolled steel reinforcement

PurposeAlthough separate studies on the influence of corrosion and fire exposure on the constitutive relationship of concrete and steel have been done, there is still a gap in knowledge on the influence of corrosion-temperature superimposition as nonlinear phenomenon. The current study is focused to investigate the response of hot-rolled steel bars subjected to corrosion-temperature superimposition.Design/methodology/approachUsing the accelerated corrosion-impressed-current technique, hot-rolled specimens with different levels of corrosion were obtained. The hot-rolled rebars were first corroded to target levels such as (6, 12, 18, 24, 30 and 36%) and subsequently subjected to target temperatures (250 °C, 400 °C, 550 °C, 800 °C and 950 °C), before tensile tests were carried out to evaluate the residual mechanical response.FindingsThe outcomes showed a significant decline in the parameters governing the mechanical properties of steel reinforcement due to the combined damage due to corrosion and fire. Corroded reinforcement still showed ductile failure after exposure to fire. Moreover, the combined loss of load-bearing characteristics due to corrosion and fire has little influence on the modulus of elasticity. The outcomes of this investigation provide a theoretical database for the assessment of aged structural elements exposed to combination after exposure to fire.Originality/valueThe information concerning structural material's response to corrosion-temperature combined damage is still limited. The cover of the reinforcement is designed to safeguard the reinforcing bars from foreign agencies but is often damaged and spalled off due to corrosion, rendering the reinforcing bars directly exposed. The study aims at the experimental production of fire conditions in a corrosion-damaged infrastructure to cover the aforementioned research gap. The effects of corrosion being superimposed by exposure to elevated temperatures on key parameters affecting mechanical behavior were examined.HighlightsInfluence of corrosion-temperature superimposition on the mechanical properties of hot-rolled rebars.Influence of corrosion-temperature superimposition on the macro and microstructure properties of hot-rolled rebars.Influence of corrosion-temperature superimposition on stress-strain curves of hot-rolled rebars.Influence of corrosion-temperature superimposition on tensile strength, modulus of elasticity and elongation of hot-rolled rebars.

Study on Mechanical Characteristics and Durability of Prestressed Anchorage Structure of Rock and Soil under Fatigue-Corrosion Coupling Action

This paper presents a comprehensive approach encompassing indoor experiments, theoretical analysis, and numerical simulations to investigate the durability of prestressed anchorage structures subjected to fatigue loads and corrosion. The study addresses the critical issue of gradual aging and damage caused by cumulative loads and corrosion, which ultimately leads to a decrement in structural durability. Through a rigorous analysis of the effects of fatigue load and corrosion on the performance of steel bars, numerical simulations were conducted to elucidate the failure mechanisms and variation patterns within the internal anchoring section. After subjecting steel bars to fatigue and corrosion tests for a defined duration, they were systematically categorized and exposed to varying fatigue tensile cycles in diverse acidic and alkaline environments. Employing the PFC2D program, a numerical model of the prestressed anchorage structure under the coupled effects of fatigue load, corrosion, and fatigue load was developed. This model allowed for a comparative analysis of the evolution of shear stress, axial stress, and displacement fields at the bolt-grout interface under two distinct conditions. The findings reveal the microscopic mechanisms underlying bond degradation at the bolt-grout interface under the synergistic impact of fatigue load and corrosion. The proposed methodology and experimental results demonstrate that geotechnical anchoring technology can effectively reinforce up to 70% of geotechnical structures, significantly reducing soil loss by approximately 80%. This research provides valuable insights into the durability of prestressed anchorage structures, paving the way for future improvements and optimizations.

Effect of seawater corrosion on the mechanical properties of basalt fiber reinforced polymer composites modified by silane coupling agent KH560 and carboxylated carbon nanotubes

Basalt fiber reinforced composite (BFRP) has been widely used in various engineering fields, while the corrosion resistance of BFRP in harsh environments needs to be improved. In this work, the effects of seawater corrosion on mechanical properties of silane coupling agent (KH560) and carboxylated carbon nanotubes (CNTs) modified basalt fiber reinforced epoxy resin composites (BF/EP) were studied by simulating seawater corrosion under different conditions. The results showed that with the increase in corrosion time and temperature, the flexural performance and interlaminar shear strength (ILSS) of the composite material significantly decreased. Under the same corrosion conditions, the modified basalt fiber composite has better corrosion resistance to seawater than the untreated one due to an enhanced "soft-rigid" multi-scale stress transfer region between the BF and resin matrix. The flexural strength, flexural modulus and ILSS of modified basalt fiber composites decreased by 17.7 %, 12.2 % and 11.3 %, respectively, after 7 weeks of seawater corrosion at 60 °C, while that of untreated basalt fiber composites decreased by 28.2 %, 20.4 % and 19.7 %, respectively. In addition, the corrosion of distilled water on basalt fiber composites was also studied. Similarly, the modified basalt fiber composites showed better corrosion resistance to distilled water compared to the untreated basalt fiber composites. The research shows that the synergistic modification of KH560 and CNTs can effectively improve the corrosion resistance of BF/EP. This work is significant for promoting the development of BFRP and its application in marine environment.

Effect of corrosion on fretting wear morphology and mechanical behaviors of wires

Corrosion and fretting wear inevitably occur in wires, which are important parts of cables. To study the wear morphology and surface mechanical behavior of wires for different fretting and corrosion times, a numerical model of fretting wear of wire with different corrosion conditions is established using MATLAB and ABAQUS software’s. Firstly, according to the surface roughness of wires under different corrosion times, the node coordinates in the numerical model are modified to simulate different rough surfaces. Secondly, the wear characteristics of wires under different fretting cycles are obtained by using a cycle jump concept and an ABAQUS user subroutine. Finally, the numerical model is validated using experimental data. The results show that when the corrosion time is 0 h, the wear area has a regular oval shape. The wear volumes of wires with corrosion times of 120 h and 480 h are the largest and the smallest, respectively. As wear volume increases, both residual surface contact pressure and stress decrease. When the corrosion time is 0 h and 120 h, the residual surface contact pressure is maximum and minimum, respectively.

Corrosion effects on bond strength in reinforced concrete with fly ash

Reinforcing steel bars provides additional strength and ductility to concrete by forming a strong bond with the concrete matrix. Corrosion of steel bars can significantly reduce the bonding effect between the steel bar and concrete, which can compromise the structural integrity and durability of reinforced concrete structures. An experimental investigation was performed to examine the influence of fly ash (FA) and corrosion on concrete–steel bond behavior. The accelerated corrosion method was employed to obtain the desired level of corrosion. The FA content, corrosion percentage, and presence of stirrups were considered significant factors influencing bond behavior. The bond–slip curves and bond toughness were used to discuss bond behaviors. The findings indicated that mild corrosion (below 2.5%) can enhance concrete–steel bond performance, and the addition of 20% FA leads to higher ultimate bond strength (τu ), significantly mitigating the decrease in bond strength caused by severe rebar corrosion. Also, this study analyzed the influence of stirrups on the bond strength of FA concrete and had a nearly insignificant effect compared to regular concrete. The results and discussions of the present study carry significant importance in the establishment of a bond–slip constitutive model under multifactor coupling conditions. Furthermore, it offers valuable insights into the design of engineering structures.

Accelerated corrosion of FeCrAlTi coating by in situ proton irradiation in molten lead-bismuth eutectic

The synergistic effect of simultaneous proton irradiation and LBE corrosion on FeCrAlTi coating is investigated, and the surface morphology, elementary composition, microstructure and crystal structure of the formed oxide scale are systematically analyzed. The results reveal the accelerated LBE corrosion behavior of proton irradiated FeCrAlTi coating, which can be attributed to irradiation produced defects leading to enhanced diffusion, irradiation induced more porous oxide scale resulting in promoted short-circuit diffusion, and irradiation enhanced adsorption energy of O, Pb and Bi on coating surface contributing to intensive interface interaction.

Flexural behavior of BFRP bar–hybrid steel fiber reinforced UHPC beams

Ultra-high-performance concrete (UHPC) has the potential to overcome the durability limitations of conventional concrete. Basalt Fiber Reinforced Polymer (BFRP) bars can mitigate the corrosion effects of steel bars and fully exploit the properties of UHPC. Industrial Steel Fibers (ISF) are a widely used component in the preparation of UHPC. To reduce environmental pollution and costs, this study proposes using recycled tire steel fibers (RTSF) instead of ISF in the production of UHPC. RTSF will be combined with BFRP bars to prepare hybrid steel fiber UHPC beams. The study investigates the effects of RTSF substitution for ISF and BFRP reinforcement ratio on the flexural performance of UHPC beams. The study indicates that the beam's bending failure modes include concrete crushing, equilibrium, and BFRP bar tensile failure. The replacement rate of RTSF has a dual effect on the flexural performance. As the RTSF replacement rate increases from 0 % to 100 %, the cracking load and ultimate capacity of the beams decrease by 2.86 % and 10.38 %, respectively, while the mid-span deflection of the beam increases by 7.94 mm when it reaches failure. When the replacement rate of RTSF is 60 %, the beams exhibit optimal bending performance, and their ultimate capacity can be increased by 2.95 % compared to the capacity when the replacement rate is 0 %. The failure mode of the beams is significantly influenced by the reinforcement ratio of the BFRP bars. Increasing the BFRP reinforcement ratio from 1.12 % to 7.12 % resulted in a 65.8 % decrease in maximum crack width and a 57.6 % decrease in mid-span deflection, while the ultimate load is increased by 78.6 %. The proposed theoretical calculation formula can effectively predict the flexural capacity of BFRP bar hybrid steel fiber UHPC beams, providing a theoretical basis for the application of FRP reinforced hybrid steel fiber UHPC beams.

Study of the corrosion protection effect of the new composition based on gossypol resin in the hydrogen sulfide formation water

We investigated the impact of a new composition (HS-1) composed of gossypol resin and IB-1 reagent taken in the ratio of 3:1 on the corrosion rate in the hydrogen sulfide formation water under laboratory conditions. Concentrations of 20, 40, 60 and 80 mg/l of the new composition were used. The formation water sample taken from well No. 1082 of "Bibiheybatneft" OGPD, SOCAR was used as an corrosion medium. The corrosion effects were also investigated at the concentrations of 50, 100, 150 and 200 mg/l of gossypol resin and 10, 15, 20 and 25 mg/l of IB-1 inhibitor. When the concentration of gossypol resin in the formation water increased by 50–200 mg/l, the corrosion protection effect took a value in the range of 60–82%. When the concentration of IB-1 inhibitor varied between 10–25 mg/l in a hydrogen sulfide medium, the protection effect was between 65–90%. Increasing the concentration of new HS-1 composition in the range of 30–80 mg/l resulted in an increase in its corrosion protection effect between 74–98%. It was found that the optimal consumption rate of gossypol resin, IB-1 inhibitor and HS-1 composition for corrosion protection in an aggressive medium with hydrogen sulfide was 200 mg/l, 25 mg/l and 80 mg/l, respectively.

Effect of Corrosion and Post-Weld Treatment on the Fatigue Behavior of Multipass Robot GMAW Welds of S700MC Steel

High-strength steel is a candidate material for offshore structures, which are currently being constructed with regular-strength steel. These structures are constantly exposed to harsh environmental conditions and experience cyclic loadings, which can lead to premature failure due to the synergistic effects of corrosion and fatigue. In this regard, the current study aims to investigate the effects of corrosion and High-Frequency Mechanical Impact (HFMI) treatment on the fatigue behavior of welded joints made of S700MC steel. Multipass butt-welded joints were fabricated via the Robot GMAW method at an optimally selected heat input of 0.7405 kJ/mm. The microstructure of the weldments was studied using light optical microscopy. Tensile and Vickers microhardness tests were performed to evaluate the mechanical properties of the welded joints. To simulate marine environment corrosion in the laboratory, the as-welded samples were exposed to salt fog spray for 720 h. Subsequently, specimens were subjected to cyclic loading to evaluate their fatigue strength, while SEM and stereomicroscopy were used to analyze the fractured surfaces, providing a comprehensive understanding of the fracture mode. The findings suggest that although corrosion led to increased surface roughness and the formation of corrosion pits, its influence on the fatigue behavior of the weldments might be less significant compared to other geometrical factors, at least for the exposure time employed in the study.

General Methods for the Analysis of Chemical Properties of Fuels

This article is the third in a series of articles focused on presenting common methods for evaluating conventional and alternative fuels. The first two articles of the series were devoted to the determination of elements and non-hydrocarbon compounds in fuels [1]) and the determination of the physical properties of fuels [2]). This text presents an overview of the chemical properties determined for individual fuels. The chemical properties, acidity and alkalinity of fuels, content of unsaturated compounds, aniline point, water content, oxidation stability, and corrosive properties of fuels are presented in this article. The main goal of the article is to provide a comprehensive overview of which fuels are monitored, why they are monitored, and what methods are used for this monitoring. The emphasis is mainly on standardized parameters and tests, but in some cases, non-standardized tests are also discussed, or (additional) determinations not required by standards. For conventional and alternative fuels, several physical chemical, or other properties are used to evaluate the quality of these fuels. In this article, we present an overview of the chemical properties that are monitored for liquid and gaseous conventional and alternative fuels. These are acidity and alkalinity, content of unsaturated compounds, aniline point, water content, oxidation stability, and corrosive effects of fuels. In the article, we present the testing methods that are used to monitor these properties. Furthermore, we also present the reasons why these properties are monitored for individual fuels. Emphasis is placed on standardized parameters and tests, i.e., those prescribed by the relevant standards for individual fuels. However, parameters and alternative methods are also discussed, which are not prescribed by any standard for the respective fuels, but are supplementary determinations. The determination of elements and hydrocarbon and non-hydrocarbon compounds in fuels potentially falls within the scope of this article. However, since two separate articles [1] were devoted to these parameters, they will not be discussed here

Mechanical responses of chemically corroded sandstone under cyclic disturbance: Insights from fatigue properties and macro-micro fracturing mechanism

Engineering rock masses are likely to be subjected to coupled chemical corrosion and cyclic load disturbance, deteriorating the internal structure of rocks and further threatening the long-term stability of engineering structures. In this study, to investigate the combined effect of cyclic loading and chemical corrosion, the cyclic uniaxial compression tests are conducted on sandstone specimens chemically corroded by different corrosion times (0, 20, 40, 60 days) and pH values (1, 3, 7, 11, 13). Our results indicate that chemically corroded sandstone specimens featured by an increase in irreversible strain and hysteresis energy density compared with natural rocks. A coupling damage variable is proposed to reflect the initial damage induced by chemical corrosion and the mechanical damage induced by cyclic disturbance, and the accumulation rate of coupled chemical-fatigue damage variables significantly increases with increasing corrosion time or enhancing acidity and alkalinity. Fatigue failure modes of tested specimens transform from splitting failure to unidirectional shear failure as corrosion time increases, and chemically corroded specimens are featured by ductile failure characteristics compared to natural state. Moreover, X-ray diffraction (XRD) and Scanning Electron Microscope (SEM) are employed to analyze the micro-fracturing mechanism of sandstone. Cement minerals dominate the reactions in acidic solutions, whereas quartz takes the lead in alkaline conditions. Due to pronounced influence of cement minerals on the macroscopic mechanical properties of sandstone, acid corrosion specimens tend to experience more severe damage. Micro-cracks inside rocks under cyclic loading have sufficient time to pass through weakly bonded particles, and chemical reactions markedly weaken inter-particle bonding degree, and thus the fatigue fracture of chemically corroded specimens predominantly exhibits intergranular (IG) fracture.

Corrosion Protection of Embedded Steel Reinforcement Using Canarium Schweinfurthiia Exudate for Coastal Concrete Structures

This experimental study evaluated the effects of corrosion on the bond behavior and structural integrity of reinforced concrete. A total of 36 concrete cube specimens containing reinforcing steel bars were divided into control, uncoated, and Canarium schweinfurthiia exudate/resin coated groups and immersed in 5% NaCl solution for 360 days. Periodic tests were conducted to analyze corrosion levels, bond strength, steel bar properties, and failure loads. Results showed the control specimens exhibited little corrosion while uncoated bars experienced significant corrosion after exposure. In contrast, exudate/resin coated bars demonstrated a substantial reduction in corrosion, indicating the coating's inhibitory effects. Pull-out bond strength and maximum slip tests consistently revealed lower strengths and higher slips in corroded samples compared to controls. However, coated specimens maintained higher bond capacities and lower displacements, validating the coating's protective performance. Measurement of bar diameters, cross-sectional areas, and weights before and after corrosion highlighted the proportional losses associated with the corrosion process. Dimensions and masses of corroded reinforcements decreased by 2-7% on average from initial values. In comparison, controls showed minimal variations. Failure load analyses found controls withstood the highest loads, while corroded members exhibited reduced capacities. Overall, the study demonstrated corrosion negatively impacts the critical steel-concrete bond and undermines composite action essential for structural integrity. Exposure to NaCl solutions markedly increased corrosion and decomposition of unprotected bars. However, natural Canarium schweinfurthiia exudate/resin coatings were highly effective at mitigating corrosion effects by preserving bond strength, slip resistance, steel geometries and load capacities close to uncorroded levels. The findings validate protective coatings as a viable solution for durable reinforced concrete design in marine environments. Proper corrosion prevention through coatings or inhibitors can help ensure structures withstand service loads over their design life.

Effect of combined microbial and stress corrosion on 7075 aluminum alloy in high salinity environment

The study investigates the impact of the combination of Gram-positive bacteria Bacillus subtilis (B. subtilis) and tensile stress on the surface corrosion of 7075 aluminum alloy (AA7075) in a high-salt solution environment. The change in PH value caused by the growth curve of bacteria was analyzed for corrosion factors. Scanning electron microscopy (SEM) and ultra-depth 3D microscopy (DOF) were used to compare the surface morphology, elements and corrosion of the samples. The presence of a biofilm reduces the corrosion rate by 0.005 ± 0.0004 mm/y and the application of a constant load results in an increase in the corrosion rate to 0.26 ± 0.013 mm/y. The applied stress leads to the disruption of both the biofilm and oxide film on the metal surface, causing a significant reduction in the impedance isolation effect, and resulting in an expansion of the average diameter and depth of the corrosion pit by 372.21 and 29.5 µm, respectively. In electrochemical impedance testing, there is an approximately 7.01×103 Ω increase in impedance value when exposed to B. subtilis environment; conversely, under stress conditions, there is a decrease by 4.02×103 Ω with B. subtilis present. The corrosion current density has increased fourfold to reach 9.15×10−6 (uA/cm2). This suggests that the combination of bacterial and stress can have a complex and detrimental impact on the corrosion behavior of aluminum alloys in high-salt environments.