Corrosion Loss Research Articles

Corrosion behavior and cellular automata simulation of carbon steel in salt-spray environment

Scanning electron microscope (SEM) and X-ray diffraction (XRD) were used to discuss the corrosion loss and morphology of the pit and rust layer of carbon steel. It was found that the corrosion process is largely influenced by the cyclic shedding of surface corrosion products, in addition to being controlled by the mechanism of oxide film shedding and pit evolution. A corrosion mechanism (the mechanism of rust layer shedding) is proposed. As a result, in this paper, the corrosion process of the test steel is simulated by the cellular automata. It was set up that the mechanism of oxide film shedding, the mechanism of pit evolution, and the mechanism of rust layer shedding in Cellular Automata Simulation. The optimal time ratio and simulation parameters were found, and a predictable cellular automata corrosion simulation model was built, providing a solution for carbon steel’s service life prediction.

The combined effect of carbon starvation and exogenous riboflavin accelerated the Pseudomonas aeruginosa-induced nickel corrosion

The primary objective of this study is to elucidate the synergistic effect of an exogenous redox mediator and carbon starvation on the microbiologically influenced corrosion (MIC) of metal nickel (Ni) by nitrate reducing Pseudomonas aeruginosa. Carbon source (CS) starvation markedly accelerates Ni MIC by P. aeruginosa. Moreover, the addition of exogenous riboflavin significantly decreases the corrosion resistance of Ni. The MIC rate of Ni (based on corrosion loss volume) is ranked as: 10 % CS level + riboflavin > 100 % CS level + riboflavin > 10 % CS level > 100 % CS level. Notably, starved P. aeruginosa biofilm demonstrates greater aggressiveness in contributing to the initiation of surface pitting on Ni. Under CS deficiency (10 % CS level) in the presence of riboflavin, the deepest Ni pits reach a maximum depth of 11.2 μm, and the corrosion current density (icorr) peak at approximately 1.35 × 10−5 A·cm−2, representing a 2.6-fold increase compared to the full-strength media (5.25 × 10−6 A·cm−2). For the 10 % CS and 100 % CS media, the addition of exogenous riboflavin increases the Ni MIC rate by 3.5-fold and 2.9-fold, respectively. Riboflavin has been found to significantly accelerate corrosion, with its augmentation effect on Ni MIC increasing as the CS level decreases. Overall, riboflavin promotes electron transfer from Ni to P. aeruginosa, thus accelerating Ni MIC.

Electrochemical studies, adsorption behavior, and spectroscopic analysis of vanadyl complex of bis(1-(pyridin-2-yl)ethylidene)malonohydrazide as efficient eco-friendly corrosion inhibitor for low carbon steel in 1M HCl

Corrosion is a destructive attack that can effect on a substance. One of the most important problems is corrosion losses, which can cause a loss of 10% of the metallic output every year. A novel VO+2 complex of N1, N3-bis(1-(pyridin-2-yl)ethylidene)malonohydrazide [(VO)2(L)(OH)2].H2O has been prepared and utilized as corrosion controller for Low carbon steel (LCS) in hydrochloric acid solution. Chemical (Weight loss (WL)), electrochemical (electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (PP)) are utilized to examine the effectiveness of prepared [(VO)2(L)(OH)2].H2O (VOL). The inhibition efficacy improved with increasing the VOL doses. The maximum efficacy of the investigated inhibitor is 96.1% at 21×10−6 M. However, at 21×10−6 M, the efficacy decreased from 96.1% to 84.4% when the temperature elevated from 298 to 318 K. The adsorption of VOL on the LCS surface was used to explain the inhibition. According to the values of ∆G°ads, which ranged from 25.8 to 21.5 kJ mol−1, the adsorption of the VOL on the LCS surface is physical adsorption. Analyzing the polarization curves of synthesized inhibitors revealed that they were mixed-type inhibitors. LCS was found to be surface inhibited when coated with a thin film of inhibitors, and surface morphology was assessed by different techniques such as scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and atomic force microscope (AFM), and X-ray photoelectron spectroscopy (XPS). Density functional theory (DFT) was employed to explain the nature of the interface among VOL and LCS surfaces. It was found that all of these used tests agreed with each other.

Research on using resistant sensor to predict corrosion under insulation of carbon steel

Corrosion under insulation (CUI) is very common and severely occurs in chemical/oil and gas industries, however, it is difficult to detect this corrosion by non-destructive testing (NDT) techniques. Carbon steel resistant sensors were used to determine CUI in this research. The output voltage values of the sensor were measured over time and from which the corrosion loss in sensor’s thickness was calculated. Carbon steel samples were exposed to the sensors under the same conditions for the same periods, and the corrosion loss of the samples was determined by weight loss. The results show that when the sensors were corroded within 10-20 % the corrosion loss of carbon steel samples is equivalent to that calculated from the output data of the sensors with a standard deviation of 6-24 %. These results demonstrate the high potential of resistance sensors in determining CUI and predicting damage of industrial components and pipes.

Effect of coarse calcareous aggregates on corrosion of steel reinforcement in marine concretes

Finely ground limestone, perhaps as part cement replacement, has been shown to reduce concrete permeability and enhance strength. Whether this holds also for coarse limestone aggregates is of both practical and environmental interest, particularly the effect on corrosion of steel reinforcement. This is confirmed herein with exposure tests over 14 years for a range of concretes exposed to a high chloride environment. Importantly, these concretes also showed delayed initiation of reinforcement corrosion and lower long-term corrosion losses compared with similar concretes made with coarse igneous or siliceous aggregates. The observations are attributed to enhanced bonding between cement-hydration products and the limestone aggregate surfaces. These findings are important both for reducing environmental impacts and greenhouse gasses and for extending the durability of reinforced concrete structures.

Trends in Longer-Term Corrosion Loss of Magnesium Alloys

The corrosion of magnesium alloys is often considered to differ in behaviour and development with time from most other metals and alloys because they show evolution of hydrogen right from first exposure. However, data extracted from the open literature indicate that magnesium alloys develop corrosion mass-loss trends with time that are consistent with the so-called bimodal pattern, which is topologically similar to those of other alloys. Examples are given of such trending for magnesium alloys under immersion, half-tide and various atmospheric exposure conditions. The critical roles of corrosion pitting and its development into localised corrosion are discussed. For high-purity magnesium alloys, the transition to longer-term corrosion, which is rate-controlled by the hydrogen evolution cathodic reaction, occurs quickly, within days. Comments are made about the application of measurements of hydrogen evolution and of electrochemical methods to make rapid estimates of shorter-term corrosion rates.

Investigation of cell-accelerated corrosion (CAC) on the CoCrMo alloy with segregation banding: Hip implant applications

Metal alloy microstructure plays a crucial role in corrosion associated with total hip replacement (THR). THR is a prominent strategy that uses metal implants such as cobalt-chromium-molybdenum (CoCrMo) alloys due to their advantageous biological and mechanical properties. Despite all benefits, these implants undergo corrosion and wear processes in-vivo in a synergistic manner called tribocorrosion. Also, the implant retrieval findings reported that fretting corrosion occurred in-vivo, evidenced by the damage patterns that appeared on the THR junction interfaces. There is no scientific data on the studies reporting the fretting corrosion patterns of CoCrMo microstructures in the presence of specific biological treatments to date. In the current study, Flat-on-flat fretting corrosion set-up was customized and used to study the tribocorrosion patterns of fretting corrosion to understand the role of alloy microstructure. Alloy microstructural differences were created with the implant stock metal's longitudinal and transverse cutting orientations. As a result, the transverse created the non-banded, homogenous microstructure, whereas the longitudinal cut resulted in the banded, non-homogenous microstructure on the surface of the alloy (in this manuscript, the terms homogenous and banded were used). The induced currents were monitored using a three-electrode system. Three different types of electrolytes were utilized to study the fretting corrosion patterns with both homogeneous and banded microstructures: 1. Control media 2. Spent media (the macrophage cell cultured media) 3. Challenged media (media collected after the macrophage was treated with CoCrMo particles). From the electrochemical results, in the potentiostat conditions, the banded group exhibited a higher induced current in both challenged and spent electrolyte environments than in control due to the synergistic activity of CoCrMo particles and macrophage demonstrating more corrosion loss. Additionally, both Bode and Nyquist plots reported a clear difference between the banded and homogeneous microstructure, especially with challenged electrolytes becoming more corrosion-resistant post-fretting than pre-fretting results. The banded microstructure showed a unique shape of the fretting loop, which may be due to tribochemical reactions. Therefore, from the electrochemical, mechanical, and surface analysis data results, the transverse/homogenous/non-banded alloy microstructure groups show a higher resistance to fretting-corrosion damage.

(Invited) Addressing Durability in Long-Life, Low-Power Fuel Cells

Fuel Cells’ scalability and energy density make them excellent candidates for different applications, especially difficult to electrify applications. Their design flexibility can also be applied to low power, long-life applications. LANL has constructed a unique design to provide continuous, low power (< 100 µW) for very long duration (multiple decades). This LANL system operates passively, without active control of cell parameters, such as temperature and humidity. In addition, the system does not require interventions like refueling or maintenance during its operational lifetime. While the application and operational conditions of the systems mentioned here differ greatly from those of light and heavy-duty vehicles (e.g. ambient temperature operation, passive water management, low current densities), many of the modes of degradation are similar, and listed below: Membrane thinningDegraded performance due to loss of electrochemical surface area (ECSA)Loss of water management due to changes in hydrophobicityIncreased cell resistance due to corrosion of cell components To better understand these degradation processes LANL has performed accelerated stress tests (ASTs) to induce and quantify the membrane thinning, loss of ECSA, hydrophobicity, and bipolar plate corrosion. Those ASTs include long term OCV holds with reactants present, high potential cycling (1-1.5 V) in flooded conditions, potential cycling to induce catalyst Ostwald ripening, and exposure of cell components to corrosive environments.

Highly Dispersed Pt on Ceria with N-Doped Carbon As High Durable Catalyst for ORR and High Tolerant to H2s and CO for HOR in PEMFCs

Proton Exchange Membrane Fuel Cells (PEMFCs) are one of the most promising clean and efficient energy conversion devices. However, carbon supported Pt-based electrocatalysts, widely used in PEMFCs, show poor stability due to the carbon oxidation and unstable Pt in practical application. Hydrogen starvation at anode and unprotected startup/shutdown of PEMFCs can arouse high potential over 1.3V resulting in severe carbon corrosion and irreversible performance loss. With increased electron conductivity, the doped metal oxides Ti3O5Mo0.2Si0.4 (TOMS) [1], Nb-TiO2 [ 2], Ta0.3Ti0.7O2 [ 3], Sb-SnO2 [ 4], W-SnOx and TiOx [ 5] show great potential as durable catalyst supports that can stand over 1.0V for PEMFCs. Furthermore, strong metal support interactions (SMSI) of Pt and the support also enhance the stability of Pt.CeO2 which exhibits good dynamic oxygen storage and release capacity, strong redox capacity, was deposited on N-doped carbon (NC) as support. Pt was highly dispersed on the CeO2/NC to form Pt/CeO2/NC catalyst. Accelerated degradation test (ADT) was carried out by sweeping voltage from 1.0V to 1.2V on a GC disk with a Pt loading of 20 μgPt·cm-2 in the oxygen saturated 0.1M HClO4 electrolyte with a scan rate of 10mV·s-1, while the Pt ring was held at 1.2V vs. RHE. Fig 1 shows the morphology of as-prepared CeO2/NC and Pt/CeO2/NC, the LSV and CV of Pt/CeO2/NC after different cycles of ADT. The specific mass activity at 0.9ViR free (im@0.9V) for oxygen reduction reaction (ORR) of Pt/CeO2/NC was 105mA×mg-1 and slightly increased about 8% after 10000 cycles.On the other hand, precious metal on CeO2 is high efficient CO oxidation catalyst [6-7] and widely applied for H2 purification from reformate gases. CeO2 was applied as H2S oxidant [8] too. This broadens the Pt/CeO2/NC as a high H2S and CO tolerant catalyst for hydrogen oxidation reaction (HOR). The high dispersion of Pt nano particle, the interaction between the poison gases and Pt and/or CeO2 was believed to contribute. The theoretical and experimental details will be presented at the symposium.Reference A. M. Esfahani, E. B. Easton. Applied Catalysis B: Environmental, 2020, 268, 118743.H. Cheng, Sankarasubramanian, I. Matanovic, P. Atanassov, V. Ramani. ChemSusChem, 2019, 12, 3468. Kumar, V. Ramani. ACS Catal. 2014, 4, 1516.Ozouf, G. Cognard,F. Maillard, M. Chatenet, L. Gu´etaz,M. Heitzmann, P. A. Jacques, C. Beauger. J. Electrochem. Soc., 2019, 165(6), F3036.T. Arai, O. Takashi, K. Amemiya, T. Takahashi. SAE Int. J. Alt. Power. 2017, 6 (1), 145.Y. Kardash1, E. A. Derevyannikova, E. M. Slavinskaya, A. I. Stadnichenko, V. A. Maltsev, A. V. Zaikovskii, S. A. Novopashin, A. I. Boronin1, K. M. Neyman. Frontiers in Chemistry, 2019, 7, 114. Maurer, J. Jelic, J. Wang, A. Gänzler, P. Dolcet, C. Wöll, Y. Wang, F. Studt, M. Casapu, J. Grunwaldt. Nature Catalysis, 2020, 3, 824.X. Zheng, Y. Li, L. Zhang, L. Shen, Y. Xiao, Y. Zhang,C. Au, L. Jiang. Applied Catalysis B: Environmental, 2019, 252, 98. Figure 1

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

The gas diffusion layer (GDL) is a key part of the membrane electrolyte assembly and is critical for the transport of fuel, oxygen and water. The GDL is made up of two layers: macroporous substrate (MPS) and microporous layer (MPL) (1). To achieve the hydrophobicity required for water management, the two layers are typically treated with polytetrafluoroethylene (PTFE) (2). In many long-term experiments, it has been observed that GDL degradation, such as carbon corrosion and PTFE loss, leads to a deterioration of water management, conductivity and mass transport (3).To solve this durability problem, a thorough and in-depth understanding of the GDL degradation mechanism is required. In this study, GDLs are subjected to an accelerated stress test to investigate degradation by chemical oxidation. GDLs are soaked in Fenton's reagent for 24 hours. The hydrophobic properties of pristine and soaked GDLs are compared based on contact angle measurements, thermogravimetry and scanning electron microscopy. In addition, the chemical composition of the solutions before and after the immersion test is analyzed using a total organic carbon analyzer and an ion chromatograph. The results show that the hydrophobicity of GDL exposed to Fenton reagent is decreased by 5 and 4 degrees for the MPL and the MPS respectively. Fig 1. depicts a decrease in surface contact angle, which is associated with surface oxidation and PTFE deterioration.AcknowledgementThis research work is performed under the project AlpeDHues (AlpeDHues / FFG 889328) which is supported by the Austrian Research Promotion Agency (FFG).References C. Csoklich, R. Steim, F. Marone, T. Schmidt and F. Büchi, ACS Applied Materials & Interfaces, 13, 9908–9918 (2021).A. Ozden, S. Shahgaldi, X. Li and F. Hamdullahpur, Progress in Energy and Combustion Science, 74, 50–102 (2019).Y. Yang, X. Zhou, B. Li and C. Zhang, Applied Energy, 303, 117688 (2021). Figure 1

UAV 3D Modeling and Application Based on Railroad Bridge Inspection

Unmanned aerial vehicle (UAV) remote sensing technology is vigorously driving the development of digital cities. For experimental objects such as large, protruding, and structurally complex steel truss railway bridge structures, commonly used oblique photography and cross-circular photography techniques can lead to blurring, missing, or lower accuracy of fine texture in the models. Therefore, this paper proposes a real-scene three-dimensional modeling method that combines oblique photography with inclined photography and compares it with oblique photography and cross-circular photography techniques. Experimental results demonstrate that the model generated by combining oblique photography with inclined photography exhibits clearer textures, more complete lines, and higher accuracy, meeting the accuracy requirements of 1:500 topographic map control points. This method plays a beneficial auxiliary role in the inspection of ailments such as steel structure coating corrosion and high-strength bolt loss in steel truss railway arch bridges.

Determination of Chemical Species Dominating the Corrosivity of Japanese Tap Water by Multiple Regression Analysis

Japanese tap water is Ca2+-poor and SiO2-rich in comparison with that of other counties. Thus, there have been few studies on its corrosivity. We sampled tap waters at 70 different sites and in different seasons in Japan, subjected the samples to chemical analysis and measured localized corrosion depth and the total corrosion loss of carbon steel placed in these waters. The average corrosion rate vavg and maximum localized corrosion rate vmax were calculated. The ratio of vmax to vavg, which was defined as localized corrosion factor LCF (=vmax/vavg), was also studied. The multiple regression method was applied to obtain the dependence of vavg (objective variable) on concentrations of chemical species (explanatory variables). In the same manner, the relation of vmax and LCF to concentrations of chemical species was derived. As a result, we showed that SiO2 and SO42− mainly dominate the corrosivity of Japanese tap water. In particular, as SO42− increased, vavg became larger and vmax became smaller. Also, as SiO2 increased, vmax became larger and vavg became smaller. The behavior of LCF was similar to that of vmax. The findings of this study will be useful for estimating the corrosivity of tap waters that have low Ca2+ and high SiO2 concentrations.

Are Corrosion and Material Loss a Threat for Titanium-Titanium Tapers in Total Hip Arthroplasty Modular Acetabular Components?

BackgroundExtensive research has reported on fretting corrosion and material loss for a variety of metal taper interfaces in orthopedic devices. For modular acetabular shell-liner constructs, the interfaces studied thus far have consisted of mixed-metal pairings, and the risk of fretting corrosion and material loss for the all-titanium (Ti) shell-liner taper junction in one ceramic-on-ceramic (COC) design remains poorly understood. We asked: do Ti shell-liner taper interfaces in COC total hip arthroplasty devices show in vivo evidence of (1) fretting and/or corrosion, and (2) quantifiable potential material loss? MethodsWe examined 22 shell-liner pairs and 22 single liners from retrieved COC components. The taper interface surfaces were assessed for fretting corrosion using a semiquantitative scoring method and imaged with scanning electron microscopy. A subcohort of components was measured with a coordinate measuring machine, and volumetric material loss and maximum wear depth were calculated. ResultsFretting corrosion at the taper interfaces was minimal to mild for 95% of liners and 100% of shells. Imaging revealed fretting marks within a band of corrosion on some implants and evidence of corrosion not in the proximity of mechanical damage. Estimated material loss ranged from 0.2 to 1.3 mm3 for liners, and 0.5 to 1.1 mm3 for shells. Maximum wear depth for all components was 0.03 mm or less. ConclusionsOur results indicate that, compared to other taper junctions in total joint arthroplasty, the risk of corrosion and material loss may be minimal for Ti shell-liner interfaces.

On the Possibility of Protecting Metals From Electrochemical Corrosion without an External Power Source

Key words: electrolyte,electric current, electrode potential, cathode, anode, electrochemical protection, galvanic circuit Electrochemical corrosion of metals is one of the most common and dangerous types of corrosion, causing enormous damage to the national economy. This type of corrosion occurs in all cases, in which metals and alloys come into contact with conductive media. Anodic and cathodic electrochemical protection are the techniques for shielding metal structures from electrochemical corrosion. In these methods, the metal structure being protected is connected to an external direct current source, and depending on the direction of movement of the electrode potential of the metal (in this case, positive or negative), anodic and cathodic electrochemical protections are distinguished. The use of an external power source makes the process energy-intensive and unprofitable. This work is based on our previous studies, in which we showed that electrochemical systems, consisting of two electrodes of the same type and a conductive medium also operate in galvanic battery mode and are characterized by low galvanic currents. Given these conditions, we connected the protected object in this medium to another metal of the same name that was either smaller or larger in certain situations in order to prevent electrochemical corrosion of metals, provided that a proper galvanic circuit was formed. Studies have shown that the corrosion losses of the electrodes in the studied acid environment amounted to only 0.035 g, while the control electrode to – 0.0468 g. Approxiamtely 2 or 3 hours after the start of the experiment, the galvanometer detects the absence of current in the circuit and the system goes into a stable passive state. The mentioned circumstance makes it possible to apply a new method of protecting metals from electrochemical corrosion, which allows it to be carried out without the use of an external current source.

Influence of Corrosion on the Bond–Slip Behaviour between Corroded Bars and Concrete

Pull-out tests were conducted to investigate the effects of corrosion of both the longitudinal bars and stirrups on the bond slip behaviour of reinforced concrete specimens. The main experimental variables include concrete strength (26.7 MPa, 37.7 MPa and 45.2 MPa) and expected corrosion loss (0%, 4%, 8% and 12%), with a total of 63 specimens fabricated. The results show that the relative bonding strength of specimens under different concrete strengths gradually decreases with increasing corrosion loss, but the higher the concrete strength is, the faster its degradation rate. The influence of stirrup corrosion on the peak slip can be ignored, but it will further aggravate the degradation of the bonding strength of the specimens. This reduction in bonding strength is linearly related to the stirrup corrosion loss. Based on the experimental results of this work and the achievements of other scholars, a modified relative bonding strength degradation model and a bond–slipbond–slip constitutive model of corroded reinforced concrete are presented by accounting for the influence coefficient of concrete strength. The results show that the constitutive model is in good agreement with the relevant experimental results.

PROTECTIVE METAL COATINGS MADE OF MOLYBDENUM ON STEEL 12Cr18Ni10Ti FOR FLUORIDE MELTS. OBTAINING, CERTIFICATION, EFFICIENCY

The successful use of molten alkali metal fluorides as an electrolyte for high-temperature devices requires the development of such reactor materials that have high corrosion resistance in melts with compositions characteristic of liquid-salt mixing reactors. This is one of the most important unresolved problems. One of the effective ways to reduce corrosion losses is to create a layer on the surface of the material that protects the metal from the corrosive effects of the environment. In this paper, molybdenum insulating coatings on steel 12Kh18Ni10Ti obtained in molten salts of various compositions and by various methods are considered as protective layers. Experiments were carried out on the electrodeposition of molybdenum coatings on structural materials based on iron (steel 12Cr18Ni10Ti). The coatings obtained by the electrochemical method are inhomogeneous and easily exfoliating. The thickness of molybdenum coatings obtained from molten salts is 8.15 and 20.34 μm on steel in FLiNaK and LiCl–KCl melt, respectively. Corrosion tests have shown the inefficiency of the molybdenum coating obtained from both chloride and fluoride melts. The corrosion rate of 12Cr18Ni10Ti steel in FLiNaK/FLiNaK + 5% CeF3 melts at 650°C and a holding time of 100 hours decreases in the following row: 12Cr18Ni10Ti + Mo (0.75/0.77 mm/year) 12Cr18Ni10Ti (0.45/0.50 mm/year).

Enhancing wear resistance of R220 rail steels by quenching and partitioning (Q&P) treatment

In this study, R220 steels were subjected to the Q&P treatment after austenitization at 900 °C for 15 min. The austenitized samples were immersed in cold, warm, and boiled water baths. The quenching step was interrupted, and the specimens were immediately placed in a furnace at 500 °C and held there for 5 min. The multiphase structure, including tempered martensite, retained austenite, bainitic ferrite, and fresh martensite, was achieved by the Q&P treatment. The wear rate of the untreated R220 rail steel was decreased by up to 89 % with a slight increase in corrosion losses. The best wear resistance was obtained in the sample cooled in warm water due to the balance between its tensile strength, toughness, and hardness.

Corrosion studies of various salt solutions on metals and alloys

Corrosion studies of various salt solutions on metals and alloys

Effect of Acid and Thermo-Mechanical Attacks on Compressive Strength of Geopolymer Mortar with Different Eco-Friendly Materials

This research examined how changing the ratios of certain substances affected the strength and durability of a specific type of building material when exposed to acid and heat. This study used various combinations of zeolite, metakaolin, slag, and Portland cement as primary materials. It also used different amounts of potassium hydroxide (KOH) to make the geopolymer mortar. The concentrations of KOH used were 8 M, 12 M, 14 M, and 16 M. The cement-based material had the highest water absorption. A total of 240 tests were conducted, including 20 samples for each mix design tested at curing times of 7, 14, 21, 28, and 90 days. The results showed that the samples made with slag base material and 8 M mixing design had the highest average compressive strength at 28 and 90 days in the acidic environment test, and the zeolite and metakaolin base material samples had the highest corrosion and weight loss, possibly due to their high specific surface and aluminosilicate origin. The samples made with slag-based material had better resistance and the highest average compressive strength in the 300 °C and 500 °C thermo-mechanical tests. The lowest average compressive strength in the thermal and mechanical stress test was related to the samples made with a metakaolin base material. The tests performed on the samples made with slag base material had better compressive strength than the three other base materials in the acid and heat tests. The zeolite-based mortar lost the most weight under 30% acidic sulfuric water. The findings suggest that changes in the molar ratios of alkaline activators can significantly affect the durability properties and strength of geopolymer mortar, and the slag-based material with an 8 M mixing design had the best performance; also, SEM analysis verified this mechanism.

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.