Accumulation Of Corrosion Products Research Articles

Water-based corrosion inhibitor for prevention and repair of reinforcement in chloride and carbonated environment

This paper explores the influence of 2-aminopyridine (2AP) as water-based migratory corrosion inhibitor (M-CoI) on the corrosion resistance of reinforcing steel bars embedded in ordinary Portland cement and pozzolanic Portland cement concrete subjected to combined chloride and carbonation ingress. Two applications of 2AP are considered i.e., preventive (applied before exposure to aggressive environment) and repair (applied after corrosion initiates). Corrosion performance was assessed using electrochemical techniques and gravimetric mass loss method. The study also examines the impact of 2AP application on chloride ion concentration and carbonation depth of both concrete systems. The compressive strength of each concrete system was also measured to study the impact of M-CoI application on strength properties. Surface condition of hardened concrete and extracted rebar was evaluated by optical microscopy. Results conclude that 2AP effectively retards reinforcement corrosion when used as preventive measure by forming a homogeneous inhibitive layer on steel. However, when used as a repair technique, localised and uniform corrosion was perceived. An attempt has been made to identify the cause of non-performance of 2AP as repair measure. It was concluded that reached concentration of 1 mM was not sufficient to reduce ongoing corrosion due to the accumulation of corrosion products. The influence of the inhibitor on chloride profile and carbonation depth was found to be insignificant. It is concluded that chloride ions initiate the corrosion mechanism, while carbonation exacerbates it, particularly in blended cement concrete. Nonetheless, inhibitor application can provide similar resistance in both concrete systems.

High temperature corrosion behavior of ADC12 aluminum alloy in oxalic acid solution

High temperature corrosion of ADC12 aluminum alloy in oxalic acid solution was investigated using weight loss, electrochemical measurements, surface technologies. The results showed that at room temperature, the aluminum alloy exhibited localized corrosion, while at high temperatures, it exhibited uniform corrosion. As the temperature rose from 30 °C to 90 °C, the rapid dissolution of its passivation film led to a 70.19% increase in the corrosion rate. After soaking for 72 h, its corrosion rate decreased by 74.35% because of the depletion of hydrogen ions and the accumulation of corrosion products. The corrosion products were mainly Al2O3 and aluminum oxalate.

Investigating the corrosion resistance of Zn and Al coating deposited by arc thermal spraying process

Carbon steel is commonly used as a structural material in offshore windmill towers. The bases of these towers, which are located in tidal and submerged zones, often face corrosion challenges in marine environments. In this study, protective Zn and Al coatings were applied to S355J2 + N carbon steels by twin-wire arc spraying. The corrosion resistance of these coatings was evaluated by immersing them in various saline solutions, including NaCl solutions, sea salt solutions, and seawater. Corrosion tests were conducted for up to 1600 h. The results indicated that the corrosion rates of the Zn coatings and the accumulation of corrosion products on the Al coatings increased with higher concentrations of the testing solutions. The corrosion products of Zn coatings tested in sea salt solutions or seawater were mainly gordaite (NaZn4(SO4)(OH)6Cl(H2O)6), whereas those tested in NaCl solutions were mainly simonkolleite (Zn5(OH)8Cl2H2O). After testing in 5 wt% sea salt solutions for 1600 h, the Zn coatings exhibited interlayer decohesion owing to the formation of an oxide layer within the laminar structure. By contrast, the Al coatings displayed a well-mixed microstructure, ensuring strong adhesion and reducing susceptibility to interlayer decohesion in saline solutions. Consequently, in the current study, the Al-coated specimens demonstrated superior performance to that of the Zn-coated specimens in saline solutions.

Achieving stable zinc metal anode by eliminating the surface heterogeneity

Aqueous zinc-ion batteries (AZIBs) are regarded as one of the promising alternatives for lithium-ion batteries in large-scale energy storage systems. However, the further development of AZIBs is limited by the challenges related to the heterogeneity of zinc anode, which arises from the harmful micro-regions and the accumulation of corrosion products. We employ a simple and effective molecular self-assembly method to modify the anode with a homogeneous (Octadecanethiol) ODT molecular layer through the combination of zinc and sulfhydryl (-SH) groups. The molecular-scale modification method can precisely repair the harmful micro-regions and ensure the homogeneity of the surface. In addition, the hydrophobic alkyl chains of the ODT molecules inhibit the corrosion reaction, thus avoiding the enhancement of heterogeneity due to the accumulation of corrosion products. Theoretical calculations and simulations show that this homogeneous molecular layer effectively eliminates the surface heterogeneity and thus has a profound impact on the deposition process. Benefiting from above, all the ODT-Zn symmetrical batteries can cycle at 5 mA cm−2 for more than 1000 h. The full battery using MnO2 cathode can cycle for more than 1000 times with a capacity retention rate is 90 %.

Corrosion behavior and microstructure analysis of butt welds of Q690 high strength steel in simulated marine environment

Steel components that have served in the marine environment for extended periods often face challenges in preventing surface damage caused by corrosion protection measures. These challenges can ultimately diminish the expected service life of structures. To investigate the corrosion behavior and time-varying effects in butt welds of Q690 high strength steel in the ocean splash zone, a macroscopic morphology analysis was conducted using various corrosion times involving indoor saltwater immersion and hot-humid cycling accelerated corrosion. Quantitative analysis of corrosion pits' size and distribution range was performed in both the weld zone (WZ) and heat-affected zone (HAZ) to establish a relationship between roughness parameters and corrosion time. Experimental results were compared with corrosion parameters of regular steel. The findings reveal a gradual reduction in metallic luster with increasing corrosion time on specimen surfaces. Moreover, a greater accumulation of corrosion products is observed in the butt weld region, leading to progressive corrosion damage. High strength steel (HSS) exhibits superior corrosion resistance compared to ordinary steel. However, the corrosion damage of HSS weld joints gradually approaches that of ordinary steel in the later stage of corrosion. Microscopic scanning indicates that the accumulated corrosion layer effectively impedes the penetration of corrosive media into the matrix's interior, while the surface microstructure transitions from pitting to corrosion pits. These research findings significantly contribute to assessing the performance and analyzing the reliability of high strength steel in marine environments.

Numerical study of the impact of blockages on the Thermal-Hydraulic performance of 19 and 61-pin Wire-Wrapped bundles with conjugate heat transfer using RANS

Liquid metal fast reactors assemblies with wire spacers present a compact rod pitch to diameter ratio. Therefore, a typical off-normal condition that may occur is the blockage accident, caused by the accumulation of corrosion products or due to the detachment of broken wires. Blockage accidents may threaten the safety performance, leading to fuel rod damage. This work presents a thermal–hydraulic analysis using the RANS k-ε Realizable model to assess the impact of blockages. The model was validated on a blocked 19-pin wire-wrapped assembly comparing cladding and coolant temperatures and pressure drop with experimental data. Then, a numerical comparison between nominal and blocked conditions on a 61-pin wire-wrapped bundle was performed, analyzing solid and porous blockages. The greatest peak temperatures were obtained for the solid blockage case. Both types of blockages resulted in a similar velocity prediction upstream of the obstruction, while major differences were found in the recirculation region.

Unveiling the effect of Al–Mn intermetallic on the micro-galvanic corrosion of AM50 Mg alloy in NaCl solution

The influence of Al–Mn intermetallic on corrosion resistance of AM50 alloy was investigated. TEM-SAED was utilized to identify microstructure and composition of the corrosion products on Al–Mn intermetallic. The electrochemistry results revealed that the corrosion rate of pure Mg was lower than AM50 due to thermodynamic driving force for micro-galvanic corrosion by Al–Mn with matrix. Although the Volta potential difference reduce because of accumulation of corrosion products, the cathodic activity of AM50 alloy increases with exposure time. The progress of corrosion could not be inhibited since the loose and porous corrosion products provided an area for containing and storing the corrosion medium.

Influence of oxalic acid on the corrosion behavior of AZ91D magnesium alloy in deionized water

Due to its light weight, Mg alloy can be applied to automotive engines and cooling systems to reduce vehicle weight, energy consumption and exhaust pollution. However, ethylene glycol-type coolants can be oxidized into oxalic acid, glyoxylic acid and other substances at high temperature, which can cause the damage of Mg alloy. In this paper, electrochemical methods, hydrogen evolution and surface analysis methods were used to study the influence of oxalic acid on the corrosion behavior of AZ91D magnesium alloy in deionized water. The results indicated that the oxalic acid accelerated the corrosion of Mg alloy, and its corrosion rate increased with the concentration of oxalic acid. However, interestingly, the corrosion rate of Mg alloy in oxalic acid solution slowed as the immersed time lengthened, which could be related to the accumulation of corrosion products and the consumption of hydrogen ions. The main corrosion product of the corrosion of Mg alloy in oxalic acid solution was composed of magnesium oxalate.

INFLUENCE OF NI AS MINORITY ALLOYING ELEMENT ON THE CORROSION BEHAVIOR OF AMORPHOUS AL-CU-MG ALLOYS IN CHLORIDE SOLUTION

The influence of nickel as minority alloying element on the corrosion behavior of amorphous alloys (Al74Cu16Mg10)99Ni, (Al74Cu16Mg10)98Ni2 and (Al74Cu16Mg10)97Ni3 was investigated. The amorphous alloys were obtained as ribbons by Chill Block Melt Spinning (CBMS). The amorphous structure of the alloys was proven by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The corrosion rate was calculated gravimetric using continuous immersion tests for 360 hours in 3.5% NaCl solution at a temperature of 25oC. The lowest corrosion rate was found in the alloy containing 3 at. % Ni. The chemical composition of the accumulated corrosion products was studied using XRD.The influence of nickel on the local corrosion resistance of the amorphous ribbons of (Al74Cu16Mg10)100-хNiх x = 0, 1, 2, 3% alloys was investigated electrochemically in a solution of 3.5% NaCl at 25°C. Pitting potential (Epitt) and repassivation potential (Erp) were determined. It was found that most resistant to pitting corrosion was the (Al74Cu16Mg10)97Ni3 alloy, which showed the noblest pitting potential (Epitt -0.332 V) and repassivation potential (Erp -0.530 V).All obtained corrosion test results of the nickel-containing amorphous alloys were compared to the base amorphous Al74Cu16Mg10 alloy.

Effect of Marble Waste Powder and Silica Fume on the Bond Behavior of Corroded Reinforcing Bar Embedded in Concrete

Bond behavior is the mutual effect and the force transmission between concrete and reinforcing bar that directly influence the behavior of reinforced concrete structures. Considering the silica fume (SF) and marble waste powder (MWP) could enhance the concrete matrix and improve its adherence, the bond-slip behavior of corroded reinforcing bar in concrete containing SF and MWP as ordinary portland cement (OPC) is examined in this work. Three of 16 concrete mixes were selected for this investigation: one control mix, a second mix containing 10% SF and 5% MWP as OPC replacements, and the third containing 10% SF and 20% MWP as OPC replacements. The pullout test was applied to the specimens with 0%, 2%, 5%, and 10% corroded reinforcement. According to the results of specimens with uncorroded reinforcement, replacing 10% of cement by SF and 5% or 20% by MWP, the bond strength between concrete and reinforcing bar increased by 27% and 13%, respectively, compared to that of the control specimens. Also, the samples containing SF and MWP showed higher corrosion resistance and their bond strength’s loss due to the corrosion of reinforcing bars was less than the control samples. The results also indicate that bond stress at low corrosion (2%) levels is partially increased because of the friction resulting from the accumulation of corrosion products on reinforcement’s surface. However, for higher corrosion levels (5% and 10%), the bond strength decreases. By comparing the two diameters of reinforcing bars (12 and 16 mm), it was recognized that the reduction of bond strength due to the corrosion is more severe in the reinforcements with greater diameters.

Comparative corrosion study of HVOF coated Wc-10Co-4Cr, NiCrBSi and NiCr industrial waste coatings on AiSi304 stainless steel

The increasing demand for the high-velocity oxy-fuel (HVOF) thermal sprayed coated steel for boiler tube applications is the driving force behind this research work. Following the needs of the industry, the present study is aimed at understanding and comparing the corrosion resistance behavior of the WC-10Co-4Cr, NiCrBSi, and NiCrIW coating on AISI 304 stainless steel. A detailed microstructural characterization of the coatings before and after the corrosion experiment by FESEM, phase identification by XRD, and porosity determination by image analysis was performed. Corrosion behaviors of the coatings are examined by the electrochemical measurement technique after their immersion in a solution of 4 % NaCl for 1 hr, 12 hr, 36 hr, 102 hr, 200 hr, and 250 hr. Electrochemical impendence spectroscopy and Potentiodynamic polarization test results show that the porosity of the coatings and interface between unmelted particle and matrix (Formation of micro-galvanic cell) are potential sites for corrosion initiation. Electrochemical impedance spectroscopy (EIS) data indicates that the corrosion resistance of all types of coating initially decreases with increasing immersion time, but after some time corrosion resistance of the coatings again increases with increasing immersion time. This is because of the local accumulation of corrosion products in the defects hindering penetration of the electrolyte easily. Both the corrosion studies revealed that corrosion resistance of the coatings is in the following order: NiCrBSi > WC-10Co-4Cr > NiCrIW.

Miniature pH detection probe for in-situ monitoring of cement paste inside

A miniature pH detection probe which was fabricated from an oxidized tungsten wire electrode and a solid-contact silver-silver chloride electrode was developed and used for monitoring alkalinity of cement pastes. The pH detection probe which was embedded in wet cement paste block showed the stable potential differences assigned to pH 12–14 for at least more than 2 months. Although the potential difference of the probe showed inconsistent values in dry cement paste, the probe recovered to show the correct values after the re-wetting of cement paste. In an accelerated corrosion test of rebar co-embedded in cement paste using a pH detection probe, the probe showed the potential difference shift in acidic direction and illustrated depassivation of steel surface, accumulation of corrosion products in the paste, and crack formation of the paste. It was indicated that the pH detection probe was effective to evaluate not only alkalinity but also the deterioration of reinforced concrete.

An investigation on the mechanisms of ant nest corrosion of copper tube in formic acid environment

AbstractCopper tubes used in air‐conditioners and refrigerators often fail due to ant nest corrosion (ANC) in formic acid environment. In this paper, corrosion behavior and corrosion mechanisms of copper tubes in formic acid (HCOOH) were analyzed by vapor corrosion tests, optical microscopy (OM), scanning electron microscope (SEM), energy‐dispersive X‐ray spectrometry (EDS). The effects of the surface condition on ANC of copper tube were also investigated. Results showed that ANC of copper tube was a spontaneous process. The surface integrity of copper tube surface oxide layer is not the decisive factor of ANC. ANC originated from the dissolution of the surface oxide layer in HCOOH, which exposed fresh copper matrix. ANC is a special electrochemical corrosion, where the copper matrix acts as an anode and the undissolved surface oxide layer acts as a cathode due to the potential difference. The accumulation of corrosion products consisting of Cu(HCOO)2 and Cu2O can produce a wedge effect and generate many microcracks until to penetrate the copper tube wall. These findings would provide a deep understanding of the corrosion behavior of copper and copper alloys.

AFM and EIS investigation of the influence of pH on the corrosion film stability of Al4Cu2Mg8Si7 intermetallic particle in aqueous solutions

The stability of corrosion films on the Q-phase (Al5Cu2Mg8Si6) under different pH environments ranging from pH 1 to pH 13 in 0.1 M NaCl solution has been investigated using Atomic Force Microscopy (AFM) and Electrochemical impedance spectroscopy (EIS). The magnitude of Rct and Rf of Q-phase was noted to vary with pH. At pH 4 and 6, the values of Rct and Rf were higher by about 3 orders of magnitude than the values at pH 1 and 13. This indicates better protection of the metal towards corrosion under neutral conditions. The polarization resistance (Rct + Rf) obtained from the fitting parameter is observed to follow the order pH 6 > pH 4 > pH 10 >> pH2 > pH12 > pH13 > pH 1. The EIS response showed a capacitive behavior. From surface topography and cross section topography characterization there were significant differences in the surface characteristics of Q-phase under different pH values. The microscopic topographic analysis suggests copious accumulation of corrosion products in near neutral environments and the lowest surface roughness was observed in the alkaline environment. Quantitative surface roughness characterization shows that a maximum surface roughness was at pH 2 which decreases with increased basicity of the environment. Results indicate that the corrosion film stability decreases with increased deviation from the neutral pH environment.

Simulation research on near-neutral electrochemical corrosion of ferrite–pearlite pipeline steel

The problem of electrochemical corrosion of buried pipelines in near-neutral electrolytes leads to defects in or even fracture of oil and gas pipelines and the leakage of natural gas. Based on the principle of material diffusion and migration, the research object established an electrochemical corrosion model under the metallographic structure of pipes with ferritic–pearlitic pipeline steel. The results show that the most severe corrosion occurs at the center of the corrosion on the surface of the pipeline steel in a near-neutral corrosive environment. In addition, due to corrosion product accumulation, the material corrosion rate increased by about 38%. The electrolyte potential near the corrosion electrode is smaller, the ion concentration near the electrode is the highest, and the mass transfer phenomenon around the corrosion electrode is obvious. When the material undergoes metallographic corrosion, the corrosion is more severe. This research method can be used to predict the electrochemical corrosion occurring in the metal structure of buried pipelines and has some guidance for the assessment of the integrity of the external surface of buried pipes.

In-situ AFM and quasi-in-situ studies for localized corrosion in Mg-9Al-1Fe-(Gd) alloys under 3.5 wt.% NaCl environment

Revealing the localized corrosion process of Mg alloy is considered as one of the most significant ways for improving its corrosion resistance. The reliable monitor should be high distinguishability and real-time in liquid environment. Herein, Mg-9Al-1Fe and Mg-9Al-1Fe-1Gd alloys were designed to highlight the impact of intermetallic on the corrosion behaviour. In-situ AFM with a special electrolyte circulation system and quasi-in-situ SEM observation were used to monitor the corrosion process of the designed alloys. SEM-EDS and TEM-SAED were applied to identify the intermetallic in the designed alloys, and their volta potentials were measured by SKPFM. According to the real-time and real-space in-situ AFM monitor, the corrosion process consisted of dissolution of anodic α-Mg phase, accumulation of corrosion products around cathodic phase and shedding of some fine cathodic phase. Then, the localized corrosion process of Mg alloy was revealed combined with the results of the monitor of corrosion process and Volta potential difference.

Corrosion Phenomena and Fatigue Behavior of Clinched Joints: Numerical and Experimental Investigations

Lightweight construction has increasingly become the focus of scientific research in recent years, not least due to the constantly increasing fuel price, which is a key factor in the economic viability of many companies. In this respect, the use of hybrid structures, made of dissimilar materials offers many advantages. However, such hybrid structures often have undesirable side effects. For example, brittle intermetallic phases are formed when aluminum and steel are welded. Clinching as a mechanical joining process does not produce such intermetallic phases since the connection is realized through form and force closure. In this process, a punch passes through two or more sheets and forms them into a permanent joint in a die. In the present work, the corrosion phenomena of an aluminum-steel clinched joint have been investigated by both experiments and numerical simulations in order to explain the superior fatigue behavior of pre-corroded joints. Therefore, the clinched joints have been corroded by a three-week salt-spray test. In addition, the electric potential and the von Mises stress are calculated under the assumption of a static loading. The results of both experiments and numerical simulations can explain the improvement in the fatigue behavior of the corroded specimens. This phenomenon can be attributed to the accumulation of corrosion products in small gaps between the joined metal sheets.

On The Stability of Passive Film for Al-Rich Multicomponent Bulk Metallic Glass Under Long-Term Immersion in Chloride Containing Solution

In this paper, the electrochemical characteristics and passive film stability of an Al86Ni6Y4.5Co2La1.5 bulk metallic glass were systematically investigated in a chloride containing solution by the combination of electrochemical impedance spectroscopy and high-resolution transmission electron microscopy observations. The results demonstrated that the evolution of corrosion could be divided into five distinct zones: film growth in the initial immersion; a complete passive film with a dynamic and stable process; the occurrence of pitting on the passive film; accumulation of corrosion products and the formation of continuous channels to failure. Interestingly, it was noted that in the second zone, the passive film achieved the highest stability at the middle of immersion due to the synergistic effect of film doping and thickening induced by the alloying of Y/La and Ni/Co. Afterwards, a gradual degradation of the passive film was observed, which was associated with the partial devitrification of the Y2O3 and La2O3 amorphous passive film. Correspondingly, the film/metal matrix interface underwent a transition from a flat interface to a curved one during the immersion, inducing the failure of the passive film. Our findings provide guidance for the design of Al-based amorphous alloys with high corrosion resistance.

Open-porous magnesium-based scaffolds withstand in vitro corrosion under cyclic loading: A mechanistic study.

The successful application of magnesium (Mg) alloys as biodegradable bone substitutes for critical-sized defects may be comprised by their high degradation rate resulting in a loss of mechanical integrity. This study investigates the degradation pattern of an open-porous fluoride-coated Mg-based scaffold immersed in circulating Hanks' Balanced Salt Solution (HBSS) with and without in situ cyclic compression (30 N/1 Hz). The changes in morphological and mechanical properties have been studied by combining in situ high-resolution X-ray computed tomography mechanics and digital volume correlation. Although in situ cyclic compression induced acceleration of the corrosion rate, probably due to local disruption of the coating layer where fatigue microcracks were formed, no critical failures in the overall scaffold were observed, indicating that the mechanical integrity of the Mg scaffolds was preserved. Structural changes, due to the accumulation of corrosion debris between the scaffold fibres, resulted in a significant increase (p < 0.05) in the material volume fraction from 0.52 ± 0.07 to 0.47 ± 0.03 after 14 days of corrosion. However, despite an increase in fibre material loss, the accumulated corrosion products appear to have led to an increase in Young's modulus after 14 days as well as lower third principal strain (εp3) accumulation (−91000 ± 6361 με and −60093 ± 2414 με after 2 and 14 days, respectively). Therefore, this innovative Mg scaffold design and composition provide a bone replacement, capable of sustaining mechanical loads in situ during the postoperative phase allowing new bone formation to be initially supported as the scaffold resorbs.

Multiscale characterization of seawater pipe erosion of B10 copper\u2013nickel alloy welded joints

In seawater pipeline, the welding joint is a non-uniform structure composed of welding seam, base metal and heat affected zone. It has inhomogeneity in chemical composition, organizational structure, residual stress, etc. As local defects and high turbulence accelerate corrosion, the welding joint is often the weakest link in pipeline corrosion. Herein, the electrochemical corrosion behavior of B10 alloy welded joint in flowing seawater is studied from macroscopic and submicroscopic viewpoints using AC impedance, linear polarization, array electrode and morphological characterization. The results reveal that the corrosion rate of weld metal (WM), base metal (BM) and heat-affected zone (HAZ) decreased with the increase of time. Combined with SEM and EDS analysis, it can be seen that the increase in time led to the decomposition and accumulation of corrosion products, which gradually enhanced the corrosion resistance of welded joints. At the submicroscopic scale, WM acts as a cathode to mitigate corrosion during the later stages of high flow rate.