Corrosion Loss Research Articles

Investigation of Gas Diffusion Layer Degradation in Polymer Electrolyte Fuel Cell Via Chemical Oxidation

The gas diffusion layer (GDL) enables and influences the internal transport of fuel, oxygen, electricity, heat and water. The GDL is made up of the macroporous substrate and the microporous layer. To achieve the hydrophobicity required for water management, the two layers are typically treated with polytetrafluoroethylene (PTFE). Degradation of GDL, including carbon corrosion and PTFE loss, affects water management, conductivity and mass transport. GDLs were subjected to accelerated stress tests by immersing them in Fenton's reagent for 24 hours. Analysis of hydrophobic properties through contact angle measurements, thermogravimetry, and energy dispersive X-ray spectroscopy indicated that the hydrophobicity of the GDL exposed to Fenton's reagent decreased. This loss of hydrophobicity is associated with surface oxidation and PTFE degradation.

Chemical composition optimization of Al2O3-TiO2 composite coatings for enhanced wear and corrosion resistance

This study aimed to optimize the chemical composition of wear- and corrosion-resistant Al2O3-TiO2 composite coatings. 2-layered and 4-layered Al2O3-TiO2 coatings were fabricated on a 316L substrate with various Al2O3 and TiO2 content (20 %, 35 %, 50 %, 65 %, and 80 % in weight) at 900 °C by sol-gel technique. Wear properties were measured by dry sliding tests against an Al2O3 ball, and corrosion behavior was determined through potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests. All Al2O3-TiO2 composite coatings consisted of α-Al2O3 and rutile phases, regardless of the chemical composition. Increasing TiO2 content significantly increased coating thickness at the same number of layers. The 2-layered configurations resulted in lower wear rates in low-TiO2 compositions, whereas the 4-layered configurations provided higher wear resistance in high TiO2-containing coatings. The high Al2O3 concentration caused extremely high corrosion rates compared to those consisting of high TiO2. Wear and corrosion losses were decreased with increasing TiO2 content due to its nanosized structure, allowing well-adhered, continuous, and less porous coating morphology. The maximum improvement in wear and corrosion resistance was obtained in the 4-layered 65 % TiO2-containing composite coating.

Realistic accelerated stress tests for PEM fuel cells: Test procedure development based on standardized automotive driving cycles

A realistic accelerated stress test (AST) was derived by applying the worldwide harmonized light vehicles test cycle on a proton exchange membrane fuel cell (PEMFC) electric vehicle to analyze degradation mechanisms in fuel cells used in automotive applications. Two commercial PEMFC stacks were tested using the AST profile at different air inlet relative humidities (50% and 70%). After 173.5 h, the tested cells show degradation rates of up to 452 μV h−1 (after 147.5 h 247 μV h−1 for the second stack) at 1.0 A cm−2. Neither open circuit voltage nor high frequency resistance clearly indicate membrane degradation. Increased activation overpotential and mass transport resistance are observed, likely caused by Pt dissolution and/or agglomeration, carbon corrosion and PTFE loss. No significant correlation between air humidity and degradation is observed. The results show the method's ability to accelerate degradation while improving the result transferability of ASTs to real applications. It is adaptable and therefore applicable for other cycles and applications.

Customizing Catalyst/Ionomer Interface for High-Durability Electrode of Proton Exchange Membrane Fuel Cells.

Commercialization applications of proton exchange membrane fuel cells (PEMFCs) are throttled by the durability issues of the electrodes prepared by using catalyst inks. Probing into a desirable catalyst/ionomer interface by adjusting the catalyst inks is an effective way for obtaining high-durability electrodes. The present study investigated quantitatively the catalyst/ionomer interfaces based on the viscosity (η) property of the isopropyl alcohol (IPA) and dipropylene glycol (DPG) nonaqueous mixture solvent for the first time. Accelerated stress test (AST) showed that η as one of the characteristic parameters of the solvent had a threshold effect on the durability of electrodes. The electrodes in the half-cell and single cell all exhibited the highest durability using IPA:DPG = 2:6 (η = 27.00 cP) as the dispersion solvent in this work, embodied by its ECSA loss rate, and the cell potential loss was minimum after AST. The ECSA loss mechanism showed that a fine catalyst/ionomer interface structure was created for the highest durability electrode by regulating the η values of the solvent, and the carbon corrosion loss (le) and Pt particle dissolution loss (ld) were weakened. Based on the molecular dynamics (MD) simulation and 19F NMR spectra results, the solvent ratio (various η and similar ε and δ) affected the dispersion states of the ionomer. For the catalyst inks with the highest durability (IPA:DPG = 2:6), the Nafion backbone and side chain presented a higher mobility behavior in the solvent and tended to show the structure of extension separation and the respective aggregation of hydrophilic/hydrophobic phases. Meanwhile, Pt slab models suggested that the side chain of Nafion more easily adhered to the Pt interface zone, while the backbone was pushed toward the carbon support interface zone as more DPG molecules distributed on the Pt surface, which reduced the dissolution of Pt particles and the corrosion of the carbon support. These catalyst/ionomer interface structures tailored by regulating the solvent η values provide insights into improving the electrode durability.

Residual Bond Strength of Highly Corroded Reinforced Concrete

Corrosion of reinforcement due to chloride attacks in the marine environment is a natural phenomenon. Corrosion of reinforcement produces corrosion products of high volume, which deteriorates the structural integrity of reinforced concrete structures due to loss of bond, cracking, and spalling of the concrete. Existing literature has documented tests investigating the bond behavior of uncorroded and corroded specimens, but there is a dearth of data pertaining to a more advanced stage (higher mass loss) of corrosion. In the current study, an accelerated corrosion test was conducted on cylindrical (lollypop) specimens, which involved utilizing an impressed current laboratory technique to induce three distinct levels of corrosion (10%, 20%, and 40% mass loss). Moreover, to assess bond strength, the pull-out tests were performed on both corroded and uncorroded specimens. The present study deals with the residual bond strength at three different corrosion levels, as a function of different parameters such as clear cover (CC), water-cement (W/C) ratio, and two different reinforcement diameters. Experimental data reveals that the mass loss achieved is lesser than the target mass loss for all specimens. It is observed that at higher corrosion levels, where the mass loss exceeds 10% or cracks appear on the surface of the reinforced structure, both an increase in mass loss and a decrease in residual bond strength is consistently observed. These effects remain consistent regardless of whether the parameters such as bar diameter, W/C ratio, and CC are increased or decreased. The statistical analysis was performed on the experimental data to develop predictive models for estimating the residual bond strength and mass loss. For higher mass loss of 30% to 35%, the corresponding bond strength for all of the specimens falls within the range of 4 Mpa to 6 MPa.

A new empirical model for flexural stiffness of corroded post-tensioned concrete beams

Under service loading and environmental actions, the corrosion of steel strands would reduce the cracking load and ultimate load of post-tensioned concrete (PTC) beams. It also leads to the degradation of flexural stiffness, and hence increases the deflection of beams under the same load. In order to more effectively evaluate the stiffness degradation of corroded post-tensioned concrete (CPTC) beams, an empirical model is proposed in this work for assessing the stiffness considering the effect of the corrosion of steel strands. In the proposed model, cracking stiffness and stiffness after cracking are assessed separately, and the equations of cracking moment and ultimate moment are derived. The proposed model is verified by experimental data. Results show that the proposed model can efficiently predict the stiffness changes during the whole loading process, and the deflections predicted by the proposed model are in good agreement with experimental values. The proposed model is proved to be able to efficiently predict the stiffness degradation of CPTC beams caused by corrosion of steel strands, and can reveal the dependence of flexural stiffness on the corrosion loss of steel strands and the external loads.

Effect of Cr addition on the Corrosion-Wear Behaviors of 18Mn(V, Mo) Steel in a Seawater Environment

The objective of this study was to examine the wear-corrosion behavior of 18Mn(V, Mo) steel, which had a minor amount of Cr addition (< 3 wt%), in an artificial seawater environment, and compare it to conventional carbon steel. A variety of electrochemical experiments, including linear polarization resistance, impedance spectroscopy, and galvanostatic polarization, were conducted, along with weight loss measurements after immersion and wear-corrosion testing. These tests aimed to determine the static corrosion and wear-corrosion mechanisms of 18Mn(V, Mo) steel with respect to Cr addition. The results of this study indicated that the addition of Cr to 18Mn(V, Mo) steel refined the V4C3 particles in the microstructure, which led to an increase in surface hardness. Moreover, the 18Mn(V, Mo) steel with Cr addition exhibited the lowest corrosion and corrosion-wear losses, compared to 18Mn(V, Mo) steel without Cr and conventional carbon steel. This beneficial effect was primarily attributed to the formation of a thin Crenriched corrosion scale that adhered to the underlying steel. This corrosion scale served as a protective barrier against the penetration of corrosive species and as a lubricant for mechanical wear. The 18Mn(V, Mo) steel with Cr addition has potential application in various industrial fields, particularly in marine and offshore environments, owing to its low corrosion-induced wear loss rate in a brine environment.

Intelligent anti-corrosion coating with multiple protections using active nanocontainers of Zn[sbnd]Al LDH equipped with ZIF-8 encapsulated environment-friendly corrosion inhibitors

The incalculable metal corrosion loss makes the research of long-term corrosion resistant coatings attract much attention. Herein, we demonstrated a new strategy for constructing a pH-responsive nanocontainer as a gatekeeper, which consisted of a laminated double hydroxide (LDH) surface in situ grown ZIF-8 containing the corrosion inhibitor of 2-mercaptobenzimidazole (MBM). The shell-core structures of the composite fillers displayed the excellent barrier performance and pH-responsive controlled release properties in epoxy (EP) coatings. Electrochemical impedance spectroscopy and salt spray tests were conducted to investigate the multifunctional role in providing an intelligent anti-corrosion MBM@ZIF-8@LDH/EP composite coating. After immersing in salt solution (3.5 wt%) for 30 days, the impedance value of the MBM@ZIF-8@LDH/EP coating at 0.01 Hz (|Z|0.01 Hz) was 2.82 × 108 Ω∙cm2, which was about four orders of magnitude higher than that of the epoxy coating (1.54 × 104 Ω∙cm2). The outstanding corrosion protection of MBM@ZIF-8@LDH was attributed to not only the compactness improvement of the composite coating, but also the anion exchange capability to act as a storage station for chloride ions. Meanwhile, the active filler could be used as a pH-responsive nanocontainer to release the loaded corrosion inhibitor of MBM and prevented further damage to the steel substrate, displaying a self-healing behavior. This strategy provides a new idea to combine perfect barrier effect and active anti-corrosion performance to prepare high-performance anti-corrosion and self-healing coatings. The multi-protective smart anti-corrosive coating would be a candidate with excellent performance for use in a variety of fields.

Probabilistic Analysis of Corrosion Rates and Degradation of Weathering Steel Bridges

AbstractCorrosion of weathering steels in outdoor conditions has been observed since their pioneering applications in construction in the 1960s. Changing environmental conditions such as decreasing SO2 concentration and changes in temperature and relative air humidity affect the formation and development of a protective layer of corrosion products on the surface of these steels. The study compares the long‐term corrosion rates of weathering steels according to EN ISO 9224 with the measured rates for various environments in the Czech Republic and abroad, with a focus on sites with high concentrations of chlorides from de‐icing salts. When considering related uncertainties, the corrosion rate models provide estimates in a wide range, and in‐situ measurements can significantly improve corrosion loss predictions. The reliability of bridges made of weathering steels with a well‐developed protective layer is insignificantly affected by corrosion. However, low reliability levels may be experienced in critical details where for example leakage may damage the protective layer of patina.

Long-term corrosion of abandoned offshore steel infrastructure

ABSTRACT A common practice in the offshore oil and gas (O&G) industry is to leave abandoned decommissioned pipelines and other steel infrastructure on the seafloor. Decisions about long-term environmental and other impacts and about the possibility of recovery require estimates of the likely long-term rate of deterioration, including corrosion loss and pit depth. These are considered as functions of time and environmental conditions including seawater temperature, dissolved oxygen concentration, salinity, seawater velocity, water pollution, microbiological activity, water depth, calcareous deposition and the effect of burial, all interpreted using established physico-chemical behaviour relevant for long-term exposures. Data for exposures up to some 600 years in seawaters are reviewed. Remaining research gaps and future perspectives of marine corrosion control are briefly discussed. Specific attention is given, by way of an example, to the influence on long-term durability of protective coatings and remnant cathodic protection, both areas in which further research is required.

Corrosion resistance of structural metals depending on the sample orientation and initial exposure conditions in coastal and rural atmospheres. Part 1. Corrosivity toward structural metals at coastal and rural test sites under various exposure conditions

ABSTRACT Four 1-year tests of metal samples (carbon steel, zinc, copper, aluminum, and D16 alloy) were carried out at locations with coastal and rural atmospheres to determine corrosion losses and the rate of chloride deposition ([Cl-]) on the upper and lower sample sides. [Cl-] were determined for different orientations relative to the sea winds on coastal sites. A methodology for testing metal samples is presented and the values of the first-year corrosion losses of metals (C1) are reported. It is shown that the corrosion of metals is significantly affected by the season of when the samples are installed. The atmosphere corrosivity under each conditions of sample exposure is estimated by the C1 values calculated using the developed dose-response functions (DRFs). It has been shown that the DRFs can be used to predict C1 and estimate the atmosphere corrosivity categories at locations with various types of atmosphere and under various exposure conditions.

Improving Pure Titanium's Biological and Mechanical Characteristics through ECAP and Micro-Arc Oxidation Processes.

Pure titanium is limited to be used in biomedical applications due to its lower mechanical strength compared to its alloy counterpart. To enhance its properties and improve medical implants feasibility, advancements in titanium processing technologies are necessary. One such technique is equal-channel angular pressing (ECAP) for its severe plastic deformation (SPD). This study aims to surface modify commercially pure titanium using micro-arc oxidation (MAO) or plasma electrolytic oxidation (PEO) technologies, and mineral solutions containing Ca and P. The composition, metallography, and shape of the changed surface were characterized using X-ray diffraction (XRD), digital optical microscopy (OM), and scanning electron microscope (SEM), respectively. A microhardness test is conducted to assess each sample's mechanical strength. The weight % of Ca and P in the coating was determined using energy dispersive spectroscopy (EDS), and the corrosion resistance was evaluated through potentiodynamic measurement. The behavior of human dental pulp cell and periodontal cell behavior was also studied through a biomedical experiment over a period of 1-, 3-, and 7-days using culture medium, and the cell death and viability can be inferred with the help of enzyme-linked immunosorbent assay (ELISA) since it can detect proteins or biomarkers secreted by cells undergoing apoptosis or necrosis. This study shows that the mechanical grain refinement method and surface modification might improve the mechanical and biomechanical properties of commercially pure (CP) titanium. According to the results of the corrosion loss measurements, 2PassMAO had the lowest corrosion rate, which is determined to be 0.495 mmpy. The electrode potentials for the 1-pass and 2-pass coated samples are 1.44 V and 1.47 V, respectively. This suggests that the coating is highly effective in reducing the corrosion rate of the metallic CP Ti sample. Changes in the grain size and the presence of a high number of grain boundaries have a significant impact on the corrosion resistance of CP Ti. For ECAPED and surface-modified titanium samples in a 3.6% NaCl electrolyte solution, electrochemical impedance spectroscopy (EIS) properties are similar to Nyquist and Bode plot fitting. In light of ISO 10993-5 guidelines for assessing in vitro cytotoxicity, this study contributes valuable insights into pulp and periodontal cell behavior, focusing specifically on material cytotoxicity, a critical factor determined by a 30% decrease in cell viability.

Using Metal Magnetic Memory to Evaluate the Effect of Welding Method and Weld Temperature on Magnetic Field Strength in Structural Steel.

Tests of welds are carried out inter-operatively, during the execution of the steel structure, as well as after the structure is welded, but even before its assembly. Steel structures already in service are also examined to detect potential cracks, delamination, or corrosion loss of thickness having the effect of weakening the mechanical strength of the structure. Such examinations are some the elements that comprise a structural health assessment. In this paper, the metal memory method was used to evaluate the effect of the welding method and weld temperature on the change in magnetic field strength. S235JR structural steel was used for the study, which was subjected to milling and MMA, TIG, and MIG welding. The results of measurement experiments carried out for each welding method are presented as graphs.

Corrosion Resistance of Zinc and Zinc-Aluminum-Magnesium Coatings in Atmosphere on the Territory of Russia.

Zinc-coated carbon steel is commonly used in the construction of buildings, infrastructure objects such as roads and bridges, automotive production, etc. Coatings based on zinc-aluminum-magnesium alloys that may have better corrosion resistance than zinc have been developed. The coatings made of the new alloys have been available on the market for a shorter period of time than conventional zinc coatings. This paper presents data on the corrosion resistance of zinc and zinc-aluminum-magnesium coatings on carbon steel obtained by tests in four locations in Russia with marine and non-marine atmospheres. Four one-year exposures at the beginning of each season and two-year tests were performed. It is shown that the corrosion resistance of the coatings depends significantly on the beginning of the exposure. The categories of atmosphere corrosivity in relation to the coatings were determined at each location. Based on the dose-response function (DRF) for zinc developed for the territory of Russia, DRFs for the coatings were obtained. A match between the categories of atmosphere corrosivity determined by the first-year corrosion losses and estimated from the values of corrosion losses calculated using the DRF is shown. Based on the data of two-year tests, the variation in the corrosion rate over time is obtained. The corrosion rates of the coatings in the territory of Russia are compared to the corrosion rates of coatings observed in various locations around the world. An approximate estimate of the service life of the coatings at the test sites is given.

Thin 1,2,4-Triazole Films for the Inhibition of Carbon Steel Corrosion in Sulfuric Acid Solution

Etching of steel items in sulfuric acid solution is used in various human activities (oil and gas industry, metal production, utilities, transport, etc.). This operation is associated with significant material costs due to corrosion losses of the metal. It has been found that an efficient way to prevent corrosion of steel in sulfuric acid solution involves the formation of thin protective films consisting of corrosion inhibitor molecules of triazole class on its surface. It has been shown that the protection of steels with a 3-substituted 1,2,4-triazole (3ST) in H2SO4 solution is accompanied by the formation of a polymolecular layer up to 4 nm thick. The 3ST layer immediately adjacent to the steel surface is chemisorbed on it. The efficiency of this compound as an inhibitor of corrosion and hydrogen absorption by steel is determined by its ability to form a protective organic layer, as experimentally confirmed by XPS and AFM data. The kinetic constants of the main stages of hydrogen evolution and permeation into steel in the H2SO4 solution were determined. A significant decrease in both the reaction rate of cathodic hydrogen evolution and the rate of hydrogen permeation into steel by the triazole in question was noted. It has been shown that the preservation of the metal plasticity in the acid medium containing the triazole under study is due to a decrease in the hydrogen concentration in the metal bulk.

Generalized Encapsulations of ZIF‐Based Fe–N–C Catalysts with Controllable Nitrogen‐Doped Carbon for Significantly‐Improved Stability Toward Oxygen Reduction Reaction (Small 25/2023)

Fe–N–C Catalysts In article number 2207671, Jia Li, Jianguo Liu, and co-workers develop a highly-catalytic Fe–N–C catalyst with a power density of >1 w cm−2 and prolonged lifetime (>40 h) using a controllable and efficient N–C coating strategy. The authors investigate the correlation between coating thickness and electrochemical performance. They also identify the stability improvement mechanism to the reduced carbon corrosion and iron loss in catalyst.

Nonlinear behaviour of corrosion damaged low-strength short reinforced concrete columns under compressive axial cyclic loading

New codes have recently introduced seismic detailing for new structures. However, there are still older reinforced concrete (RC) structures without proper ductile detailing for earthquake resistance in seismic-prone areas. These structures are further impacted by the corrosion of their embedded reinforcing bars, which further reduces the strength and ductility under axial cyclic loading. This paper summarises the results of an experimental investigation performed on low-strength short RC columns, with different confinement configurations, subject to varying degrees of corrosion to investigate their structural responses to axial cyclic loading. The experiment was conducted on 30 short RC columns (square and circular) with three levels of confinement and steel reinforcement corrosion loss ranging from 0% to ∼ 30% subjected to cyclic compressive loading. The test results show that corrosion and inadequate confinements have a significant negative impact on the structural responses of corroded columns.

Corrosion of steel rebars across UHPC joint interface under chloride attack

Corrosion of steel rebars across ultra-high-performance concrete (UHPC) joint interface under chloride attack is experimental investigated in the present study. The cases of concrete joint interface with normal concrete (NC) and high-performance concrete (HPC) are also investigated as the contrast. Twelve specimens are prepared and subjected to corrosion test. The corrosion potential and corrosion current density are measured to monitor the corrosion evolution of steel rebars. The effects of chloride concentration and cracking on the corrosion of steel rebar across the concrete joint interface are clarified. And the corrosion characteristic of steel rebars with a high corrosion loss are further investigated through the accelerated corrosion method. Results show that steel rebars across joint interface trend easily to be corroded for all the three cases with NC, HPC and UHPC. Corrosion of steel rebar across UHPC joint interface is just a little slower or slighter than the other cases across NC and HPC joint interface. The corrosion of steel rebars is highly centralized and localized at the joint interface for the case with UHPC, but relatively uniform without significant difference around the joint interface for the other cases with NC and HPC. Corrosion of steel rebars across concrete joint interface is sensitive to chloride concentration and interface cracking, especially for the case with UHPC.

“Electrons-siphoning” of sulfate reducing bacteria biofilm induced sharp depletion of Al­-Zn-­In­-Mg-­Si sacrificial anode in the galvanic corrosion coupled with carbon steel

The microbiologically influenced corrosion (MIC) of Al­-Zn-­In­-Mg­-Si sacrificial anode coupled with X80 carbon steel induced by sulfate reducing bacteria (SRB) was investigated. Results revealed that SRB strongly promoted the galvanic current density between the aluminum anode and carbon steel by facilitating the cathodic process of the galvanic corrosion on carbon steel. In the medium with SRB, 73.7% of the corrosion loss of aluminum anode coupled to carbon steel was caused by the enhanced galvanic corrosion. SRB biofilm on the carbon steel continuously obtained electrons from the aluminum anode, which was like an “electrons-siphoning” process in the galvanic corrosion.

Erosion evolution and mass loss of polyimide in AO environment using 3D Monte Carlo method

Polyimide films coated on the surface of satellites are exposed to atomic oxygen (AO) environment during service. This will suffer variation of microscopic structure and morphology, leading to corrosion and mass loss in macroscopic. In this work, a 3D undercutting model based on Monte Carlo method (MC) and Ray Tracing method was constructed, with which the AO related erosion feature of polyimide film was evaluated. Then, we predicted the evolution of erosion cross-section of the coated material with defect of different sizes and shapes exposed in higher AO fluence. The macroscopic mass loss was derived by the eroded microscopic volume and material density, during which the actual roughness was considered in our proposed undercutting model. This work provides insights into the study of microscopic 3D erosion morphology and connects with macroscopic mass loss in experiment at higher fluences.