Corrosive Agents Research Articles

Efficient and reliable corrosion control for subsea assets: challenges in the design and testing of corrosion probes in aggressive marine environments

Abstract This review discusses the challenges in designing and testing corrosion probes for aggressive marine environments. The objectives are to analyze existing literature, identify methodological problems, and highlight research gaps in subsea corrosion control. To achieve these, a comprehensive review of relevant literature was conducted, focusing on factors like high salinity, fluctuating temperatures, and the presence of corrosive agents. The methods involved synthesizing information from peer-reviewed articles, industry reports, and academic publications to thoroughly analyze current state of knowledge. The findings of this review highlight the need for standardized testing protocols, improved understanding of material compatibility, and consideration of real-world conditions in corrosion probe design and testing. Methodological problems include the lack of standardized testing protocols, limited understanding of material compatibility, and insufficient consideration of real-world conditions. These findings emphasize the challenges researchers and practitioners face in developing efficient and reliable corrosion control strategies for subsea assets. In terms of novelty and improvement, this manuscript contributes to improving corrosion control practices in aggressive marine environments by synthesizing existing literature, identifying methodological problems, and highlighting gaps. By addressing these challenges, future research can focus on developing innovative solutions and methodologies to enhance the durability and effectiveness of corrosion probes in subsea environments.

Corrosion behaviour of nitroxy-QPQ additively manufactured 17-4 PH steel on marine and nuclear reactor components

The study investigates the corrosion behavior of untreated and nitroxy QPQ treated 17-4 PH stainless steel under NaCl environments. Potentiodynamic polarization tests reveal that the nitroxy layer forms an oxide coating, leading to a passivation phase with gradually increasing current density. Oxidation at different temperatures shows variation in corrosion potential, with the lowest current density observed at 450 °C, indicating enhanced corrosion resistance. SEM images of untreated steel show severe crevice and pitting corrosion, whereas nitroxy QPQ treated surfaces exhibit reduced corrosion, with minimal disturbance at 450 °C. Elemental analysis confirms the formation of oxides and nitrides, with increased oxygen content in oxide layers and decreased nitrogen content due to the formation of chromium nitrides. The oxide layer, enriched with oxygen, nitrogen, and chromium, acts as a passive film, protecting against corrosion even in NaCl environments. Elemental mapping further illustrates the correlation between oxidation temperature and corrosion resistance, with higher temperatures resulting in reduced corrosion rates. The combined nitriding and oxidation process enhances corrosion resistance by forming a dense and adherent oxide layer, serving as a barrier against corrosive agents.

Study on the degradation of axial tensile performance of corroded bolts in steel bridges

As crucial connecting components in steel bridge structures, high-strength bolts are susceptible to corrosion from environmental factors such as corrosive agents in the air and rain during long-term service. This corrosion can reduce their load-bearing capacity, thereby threatening the safety of the entire structure. Most studies assess the degree of corrosion through mass loss, but lack a comprehensive quantitative analysis of its impact on mechanical performance. This study investigates the axial tensile performance degradation of corroded bolts based on fractal characteristics of the corroded surface and tensile mechanical performance experiments. By analyzing the fractal dimensions of corroded surfaces, which ranged between 2.026 and 2.053 for more severely damaged threads, a strong correlation was established between surface corrosion and tensile performance degradation. Bolts were classified into three categories based on fractal dimension, which quantitatively reflected the degradation of bolt tensile performance. finding that the ultimate tensile strength and load-bearing capacity decreased by 2.5–6.8 % and 1.25–5.5 %, respectively. Notably, the load at 75 % displacement dropped from 390 kN to 340 kN, a reduction of over 15 %.Finite Element Method (FEM) was used to simulate the bolt tensile process, and experimental data were used to fit damage-plastic constitutive models for bolts with different corrosion levels. The Void Growth Model (VGM) fracture criterion was employed to simulate bolt tensile fracture, predicting the axial tensile performance degradation of bolts with varying corrosion levels, and established a correction formula to quantify the impact of fractal dimension on the ultimate tensile strength of corroded bolts.This study provides a new approach for assessing corrosion impact and predicting the axial tensile performance of bolts in service.

In the LiCl-KCl melt at 500<sup>о</sup>С depending on the content of Li<sub>2</sub>О и LiOH

Molten alkali metal chlorides used in pyrotechnologies are aggressive corrosive agents. The high operating temperature of the process, the heterogeneity of the environment, and the significant corrosion activity of the molten salt necessitate both the search for stable structural materials and the development of methods for protecting the structural elements of high-temperature technological devices. Corrosion loss reduction techniques traditionally used in low temperature environments are not applicable at high temperatures. The article examines the influence of oxygen-containing impurities (lithium oxide and hydroxide) on the corrosion behavior of metallic nickel (grade NP1) – the main component of candidate structural alloys, a thermodynamically and structurally stable material in the melt for the process of electrolytic refining of spent nuclear fuel. A method for preparing the LiCl–KCl salt electrolyte and obtaining lithium oxide by thermal decomposition of anhydrous lithium hydroxide under vacuum is described, and the concentrations of impurities in the electrolyte and the synthesized lithium oxide are determined. An installation for conducting corrosion tests in an inert atmosphere of a glove box is presented. To assess the corrosion resistance of the material, the following were used: gravimetric analysis, X-ray diffraction analysis of the surface and cross-sectional sections, and X-ray diffraction analysis of the surface of the samples. The dependences of the corrosion rate of the material on the concentration of oxygen-containing additives Li2O and LiOH were obtained. Based on a combination of gravimetric, X-ray microspectral and X-ray phase analysis data, it was established that metallic nickel samples demonstrate high corrosion resistance in the studied melts with the introduction of Li2O and LiOH additives.

Corrosion Assessment in Reinforced Concrete Structures by Means of Embedded Sensors and Multivariate Analysis—Part 2: Implementation

The economic cost of repairing corrosion-affected reinforced concrete structures (RCSs) means that reliable and accurate assessment and early detection methods must be sought after. Conventional techniques, such as visual inspections, or measuring either cover layer resistivity or the corrosion potential, are methods that require accessibility and involve personnel having to travel to take in situ measurements. Monitoring by embedded sensors is a much more efficient approach that allows early detection by remote sensing. This work presents the implementation of a new measurement protocol regarding the existing monitoring system called INESSCOM (Integrated Sensor Network for Smart Corrosion Monitoring). Along with the corrosion intensity measurement in embedded sensors, it also proposes monitoring the double layer capacity of the sensors’ responses. It aims to determine, along with the rebars’ corrosion rate, the triggering agent of the corrosion process. This study was carried out using three reinforced concrete scaled columns that were exposed to different environments. The results demonstrate with this new protocol that the remote INESSCOM monitoring system can establish the corrosion rate and identify the precursor agent of corrosion (carbonation or chlorides), even when the recorded corrosion rates are similar.

Synthesis and Mechanism of a Green Scale and Corrosion Inhibitor.

A new green water treatment agent, a poly(aspartic acid)-modified polymer (PASP/5-AVA), was synthesized using polysuccinimide and 5-aminovaleric acid (5-AVA) in a hybrid system. The structure was characterized, and the scale and corrosion inhibition performance were carried out with standard static scale inhibition and electrochemical methods, respectively. The mechanism was explored using XRD, XPS, SEM, and quantum chemistry calculations. The results indicated that PASP/5-AVA exhibited better scale and corrosion inhibition performance than PASP and maintained efficacy and thermal stability of the scale inhibition effect for a long time. Mechanistic studies indicated that PASP/5-AVA interferes with the normal generation of CaCO3 and CaSO4 scales through lattice distortion and dispersion, respectively; the combined effect of an alkaline environment and terminal electron-withdrawing -COOH groups can induce the stable C- ionic state formation in -CH2- of the extended side chain, thus enhancing its chelating ability for Ca2+ ions. At the same time, the extension of the side chain length also enhances the adsorption ability of the agent on the metal surface, forming a thick film and delaying the corrosion of the metal surface. This study provides the necessary theoretical reference for the design of green scale and corrosion agents.

The corrosion inhibition performance of a diissocyanate-imidazole based organic compound during acid cleaning of MSF desalination plant

Inorganic scale formation is a common issue in multi-stage flash (MSF) desalination plants, significantly impacting operational efficiency. To address this, acid cleaning is frequently employed, but it can lead to severe corrosion of alloy components if not properly controlled with corrosion inhibitors. This study investigates the effectiveness of toluene-2,4-diisocyanate-4-(1H-imidazole-ly) aniline (TDIA) as a corrosion inhibitor for 304L stainless steel in a simulated acid cleaning solution (1M HCl and 3.5 % NaCl). A range of tests, including electrochemical analysis, weight loss measurements, and surface characterization techniques such as AFM, EDS, and SEM, were used to assess the inhibitor's performance at temperatures of 25, 45, 65, and 90 °C. At a concentration of 50 ppm, TDIA achieved inhibition efficiencies of around 90% at 25 °C and above 80% at 90 °C, demonstrating effective protection across all temperatures studied. The adsorption behavior of TDIA followed the Langmuir adsorption model, and it acted as a mixed-type inhibitor by forming a protective layer on the metal surface, which prevents corrosive agents from accessing the steel. The dual-environment testing method, simulating conditions in desalination plants, offers valuable insights into the inhibitor's practical performance, enhancing the applicability of these findings to real-world industrial scenarios.

Investigating the Corrosion Inhibition Performance of a Novel Coconut Oil-Based Poly(urethane-urea) Hybrid Coating on Carbon Steel in 3.5% NaCl Solution

Polyurethane has been used for years as an anti-corrosion coating due to its intrinsic hydrophobic properties. However, its hydrophobicity is not enough to inhibit the permeation of corrosive agents; thus, incorporating it with polyurea would further enhance its hydrophobic properties. In this study, coconut oil, a saturated, low molecular weight vegetable oil, was employed as an eco-friendly precursor for synthesizing a novel poly(urethane-urea)- based hybrid coating. The synthesis process involved the utilization of a coconut oil-based polyol blend, triethanolamine (TEA) as an amine source, and hexamethylene diisocyanate (HDI). The resulting hybrid coating on carbon steel demonstrated remarkable anticorrosion performance in a 3.5 wt. % NaCl solution, owing to the intrinsic hydrophobic characteristics of coconut oil and polyurea. Significant corrosion rate reduction was observed with increasing amine content, accompanied by an enhancement in mechanical properties. Notably, an amine loading of 4% consistently exhibited superior corrosion resistance and mechanical performance in the hybrid coating. Chemical structural analysis revealed a hydrogen-bonding network in polyurea coatings, reducing porosity, enhancing barrier properties, and improving mechanical characteristics, highlighting its potential for sustainable corrosion protection.

Progressive hollow engineering induced raspberry-like magnetoelectric microspheres via synergistic etching-assembly strategy toward boosted microwave attenuation

Optimizing the electromagnetic (EM) properties of composites through elaborate tailoring of their microstructures has become an attractive research branch, but determining the correlations between morphology, composition, and performance remains challenging. Herein, a novel progressive hollow engineering strategy is proposed for the construction of hollow CuFe Prussian blue analog (CuFePBA, CF) precursors with asymptotic variations of cavities and PBA units based on a synergistic etching-assembly approach, subsequently combined with a polydopamine (PDA) coating and carbothermal process to acquire raspberry-like hollow Cu/Fe/Fe3C@NC (CFC) composites. The proposed approach addresses the drawbacks caused by organic ligand depletion or corrosive agent usage. We then present a systematic investigation of the mechanism by which the progressive hollow engineering-induced concurrent evolution of hollow cavities, phases, defects, and inhomogeneous interfaces contributes to the improvement of the dielectric properties of the CFC samples. An optimal reflection loss (RLmin) of − 65.17 dB at 3.29 mm was realized for the CFC-2 sample and the CFC-3 sample achieved an effective absorption bandwidth (EAB) of 4.4 GHz at an ultra-thin thickness of 1.29 mm. This work reveals the synergistic effects of compositional, interfacial, and defect variations on the EM wave attenuation properties of the composites, and will provide new design inspiration for novel absorbers with modulatable hollow architectures.

Fatty Imidazolines as a Green Corrosion Inhibitor of Bronze Exposed to Acid Rain

Acid rain is one of the primary corrosive agents on bronze exposed to the atmosphere. Bronze naturally forms a layer of oxides on its surface called patina, protecting it from corrosion. However, when exposed to acid rain, this layer dissolves, making it necessary to use a corrosion inhibitor or stabilize the patina. This study investigated fatty imidazolines derived from agro-industrial waste bran as a corrosion inhibitor of SAE-62 bronze in simulated acid rain (pH of 4.16 ± 0.1). Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curve (PC) measurements were used to evaluate corrosion inhibition efficiency, which was 90% for an inhibitor concentration of 50 ppm. The EIS measurements showed that the fatty imidazolines formed a protective film that stabilized the patina on the bronze surface to a certain extent by hindering the charge transfer process. SEM–EDS analyzed the morphology and composition of the protective oxide layer. The results were complemented by Raman spectroscopy and XRD analysis, indicating cuprite, tenorite, cassiterite, and covellite in the patina layer formed on the bronze surface. The SEM analysis showed that the protective coating on the bronze surface was homogeneous using a 50-ppm inhibitor concentration. The XRD analysis suggested the presence of an organic complex that stabilizes the corrosion products formed on the bronze surface.

Tailoring the mechanical strength and corrosion resistance of aluminum matrix composites through biochar reinforcement at varied weight percentages

This study introduces an innovative approach to fabricate aluminum matrix composites strengthened with biochar, derived from renewable biomass sources. A systematic investigation of varying biochar weight percentages (0, 2.5, 5, 7.5, and 10 wt%) reveals substantial improvements in mechanical properties and corrosion resistance. Mechanical assessments, including compressive strength and hardness, demonstrate a significant enhancement in mechanical strength with biochar incorporation. In this study, it was discovered that the composite with 7.5 wt% biochar exhibits an optimal balance, displaying an 8.83% increase in compressive strength and a 15.15% rise in hardness compared to the base aluminum matrix. The study further evaluates corrosion behavior through electrochemical analyses and immersion tests in 3.5% NaCl corrosive environments, highlighting the superior corrosion resistance of biochar-reinforced composites. Corrosion rates decrease by 73% in the composite with 10 wt% biochar for the 24 h immersion time, affirming its protective barrier against corrosive agents. This research provides quantitative insights into tailoring mechanical and corrosion properties in aluminum matrix composites through biochar reinforcement, offering a promising avenue for sustainable material development. The resulting materials exhibit not only an 8.83% increase in mechanical strength but also a 73% reduction in corrosion rates, offering valuable uses in industries that need strong, eco-friendly solutions.

Anticorrosion properties of flavonoids for rust-free building materials: a review

Abstract Rust-free building materials are crucial for ensuring the durability and structural stability of constructions. Corrosion, a widespread issue affecting metals like steel, copper, and concrete, can be effectively managed with the help of corrosion inhibitors. One effective method for corrosion inhibition involves the application of corrosion-inhibiting coatings, which form resilient and tightly adherent films on metal surfaces. Flavonoids, renowned for their diverse biological activities, demonstrate significant anticorrosive properties. They contain beneficial compounds such as antioxidants and chelating agents. The efficacy of plant extracts as corrosion inhibitors is influenced by their organic constituents, particularly phenols and flavonoids. Flavonoids act by creating a protective film that serves as a barrier, shielding the metal surface from corrosive agents and limiting their access to the metal. This contributes to the prevention of corrosion. The integration of flavonoids into building materials has the potential to transform corrosion prevention practices, leading to improved durability, reduced maintenance costs, and a more environmentally friendly built environment. This article explores the promising prospects of flavonoids as an innovative and sustainable approach to corrosion prevention in building materials. Additionally, it aims to stimulate further research endeavors, fostering the development of effective and eco-friendly corrosion protection strategies for the construction industry.

Shielding against erosion: Exploring the effectiveness of pre-erosion surface corrosion inhibitors

This study investigates the corrosion inhibition effect and adsorption process of two imidazoline corrosion inhibitors, HEIE and TDEI, on pre-eroded X65 steel surfaces. Analysis of weight loss and electrochemical measurements suggests that the irregular structure of pre-eroded surfaces may impede the uniform adsorption of corrosion inhibitors, resulting in reduced effectiveness pre-erosion. Particularly, at a 30° angle of pre-erosion, corrosion inhibition efficacy is observed to be at its lowest. The corrosion inhibition rates of HEIE and TDEI on X65 steel surfaces are found to be 11.9 % lower under pre-eroded conditions at a 30° angle compared to non-eroded surfaces at the same angle. Molecular dynamics (MD) simulations support these findings, indicating that TDEI exhibits lower energy bandgap values and more negative adsorption energies (Eads) compared to HEIE, aligning with experimental results. Moreover, TDEI demonstrates a smaller diffusion coefficient for corrosive agents than HEIE, suggesting stronger adsorption efficiency and a more pronounced protective effect. Study of the corrosion inhibition effect on pre-eroded surfaces provides new ideas and methods for improving protective measures.

An Electrochemical Phase Field Model Applied to Molten Salt Dealloying Corrosion of Ni-Alloys

Metal alloys in contact with molten salts are known to corrode via a dealloying process, wherein the less-noble alloy elements (e.g. Cr) are selectively oxidized and dissolved, leaving behind a corroded structure that is enriched in the more-noble elements (e.g. Ni). In some cases, this can lead to molten salt infiltration into the alloy through discrete channels along specific microstructural features (e.g. grain boundaries). However, in other cases the dealloying process promotes a more full-scale attack of the alloy, generating a fine-scale ligament structure. This process can severely degrade the alloy’s structural integrity, which limits the practicality of these material systems in otherwise promising applications (e.g. molten salt-cooled power reactors).The thermokinetic conditions for dealloying corrosion depend on the salt chemistry and the metal microstructure, which together inform the reaction process occurring at their interface. The salt chemistry and oxidant content set the electrochemical potential for selective oxidation of the less-noble elements. The associated oxidation rate is expected to depend on the presence of an interfacial structure (e.g. double layer) and also on the transport rates of reactants towards the interface (e.g. species diffusion in the metal and oxidizer transport in the salt) and reaction products away from the interface (cation transport in the salt). The corrosion rate and morphology will also depend strongly on the rate of transport laterally along the metal-salt interface, since the reorganization of the more-noble species (Ni) towards ligament formation facilitates the attack of the alloy by the corrosive agent. It has been hypothesized that molten salts enhance this rate of solute diffusion along the metal interface.In this work, we propose an electrochemical phase field model to predict the microstructural evolution of model Ni-alloys undergoing dealloying corrosion in molten fluoride salts. The model incorporates metal oxidation and dissolution via experimentally determined redox potentials and activity coefficients for metal species in the molten salt. We show that the corrosion rate and development of pores is strongly dependent on solute transport rates within the metal and also along their solid-liquid interface. In particular, we reveal a mechanism in which grain boundaries couple with the solid-liquid corrosion front to promote rapid dealloying and molten salt attack. Oxidant content in the salt and double-layer formation at the interface are discussed for their roles in setting the electrochemical potential and reaction rate at the metal-salt interface. Finally, we discuss how the model leverages insights from atomistic modeling and highlight key knowledge gaps in the mesoscale modeling of electrochemical molten salt corrosion.

Environmental stability and ageing of ScN thin films from XPS Ar+ depth profiling

A basic knowledge on chemical stability and reactivity of a wide band gap ScN semiconductor in the presence of air atmosphere, where O2 and H2O represent the main degradation or corrosive agents, is of vital importance for a long-term performance of ScN-based devices for thermoelectric applications. Here, we present a systematic XPS Ar+ depth profiling analysis and optical and TEM characterizations of naturally room temperature air-aged thin ScN films prepared by a high-temperature DC sputtering on MgO(001) and SiO2 substrates. We find that superior crystalline quality ScN/MgO films degrade weakly after their quick initial surface oxidation and/or hydrolysis. Their oxidation is rather local and associated with the film-penetrating void-like interfaces. Significant initial surface oxidation and subsequent bulk oxidation after ageing is, however, observed for polycrystalline ScN/SiO2 films. Ab initio calculations of pure ScN and ScN with diluted nitrogen vacancies and/or substitutional oxygen impurities, which assist our experimental research, reveal pronounced impact of these defects on the ScN electronic structure. The modeled compositions reflect homogeneously and weakly oxidized films, while the real films correspond to relatively pure ScN crystallites with interfaces rich in oxygen.

Suicidal corrosive ingestion in diabetes mellitus patient: what should we do?

The corrosive agent is often used for suicide plans, and it can cause severe damage, including various gastrointestinal pathologies such as strictures, perforation, and bleeding. In more severe cases, it can lead to multiorgan system failure, disseminated intravascular coagulation, and sepsis. These was a reported case of corrosive ingestion with diabetes mellitus as a comorbidity. Prompt, appropriate, and immediate initial management by healthcare professionals is crucial to reduce complications from corrosive agents.

Influence of the boriding thermal cycle of a cladded Inconel 718 layer on both in situ age hardening as well as wear and corrosion behavior

Nickel-based superalloys exhibit exceptional suitability for operating in environments characterized by corrosive agents and elevated temperatures. Strategic allocation of this expensive material solely to the functional surface areas yields significant economic advantages. The poor tribological property profile of Inconel 718 can be significantly improved through a boriding process. In this study, the possibility of combining a coating process with boriding technology and in situ heat treatment was investigated. Layers of Inconel 718 were deposited to an austenitic stainless steel using wire-based electron beam cladding (EBC) and subsequently subjected to boriding. Based on results from annealing experiments, boriding treatments were performed at various temperature/time regimens with the aim of inducing in situ age hardening during boriding. The focus was on the investigation of the influence of the temperature/time regime during boriding on the microstructure and hardness, as well as examining the wear and corrosion behavior of the resulting borided layers. The results showed that the desired target hardness range was achieved after in situ aging with all boriding variants. Furthermore, it was demonstrated that boriding significantly improved the wear resistance but decreased corrosion resistance.

Experimental investigation on Nano-Al2O3 and hydroxypropyl methyl cellulose (HPMC) modified cement-based coatings for corrosion resistance

In this work, cementitious coatings doped with nano-Al2O3 (NA) and hydroxypropyl methyl cellulose (HPMC) were prepared in order to enhance corrosion resistance of steel bar. The electro-chemical behaviors and corrosion inhibition properties of coated steel bar and tensioned coated steel bars (subjected to 10 %, 30 % and 50 % yield load) were analyzed in 3.5 wt% NaCl solution for 840 h (35 days). At the end of electrochemical test, coating overall performance was evaluated by visual inspection. In addition, scanning electron microscopy (SEM), transmission electron microscopy (TEM) with energy dispersive spectroscopy (EDS) were used to examine microstructure and elemental composition of coatings. To comprehend the anti-corrosion mechanism of the coatings, X-ray diffraction (XRD) and infrared spectroscopy (FTIR) analysis to characterize products composition and chemical groups. Test results obtained by linear polarization resistance and electrochemical impedance spectroscopy indicated that both tensile and non-tensile coatings resistance show an increasing trend followed by a decrease with increasing NA content. Cementitious coatings incorporating 1 % NA and 0.12 % HPMC by weight of cement exhibited the best corrosion protection. The LPR fluctuates around 3700 Ω cm2, which is about twice as much as a single doped NA coating. Whether subjected to tensile loads or not, OCP values for all coated steel bar were below −0.273 V/SCE, indicating has a 90 % probability of being in active-corrosion. The corrosion resistance of tensioned coated bars decreased as time and increased load level. According to SEM and TEM image, HPMC forms a thin and continuous film on the substrate surface, which acts as a barrier to the penetration of moisture and corrosive agents. Coatings doped with 1 % NA and 0.12 % HPMC formed denser integrated polymer films at the microscopic. FTIR and XRD results showed that coating incorporated NA consumed the cement hydration product Ca(OH)2 to generate more nanofibers filling pores and microcracks. Coatings incorporating HPMC show better resistance to carbonization.

The excellent performance of oxygen evolution reaction on stainless steel electrodes by halogen oxyacid salts etching

Development of low-cost, efficient, and stable electrocatalysts for oxygen evolution reaction (OER) is the key issue for a large-scale hydrogen production. Recently, in-situ corrosion of stainless steel seems to be a feasible technique to obtain an efficient OER electrode, while a wide variety of corrosive agents often lead to significant difference in catalytic performance. Herein, we synthesized Ni-Fe based nanomaterials with OER activity through a facile one-step hydrothermal etching method of stainless steel mesh, and investigated the influence of three halogen oxyacid salts (KClO3, KBrO3, KIO3) on water oxidation performance. It was found that the reduction product of oxyacid salts has the pitting effect on the stainless steel, which plays an important role in regulating the morphology and composition of the nanomaterials. The KBrO3-derived electrode shows optimal OER performance, giving the small overpotential of 228 and 270 mV at 10 and 100 mA cm−2 respectively, a low Tafel slope of 36.2 mV dec−1, as well as durable stability in the long-time electrolysis. This work builds an internal relationship between the corrosive agents and the OER performance of the as-prepared electrodes, providing promising strategies and research foundations for further improving the OER performance and optimizing the structure of stainless steel electrodes.

Grafted sepiolite as smart nanocontainer for Daphne Gnidium plant extract: PH-dependent controlled release and effective green anti-corrosion coating

This study focuses on advancing the development of environmentally sustainable and efficient active anti-corrosion coatings for metal substrates in various engineering applications. A novel smart anti-corrosive container was developed using fibrous sepiolite clay (Sep). Sep was first subjected to grafting with 3-Aminopropyl-diethoxy-methylsilane (APDEMS). Subsequently, the grafted-Sep (Sep-G) was used to load a Daphne Gnidium plant extract (DGE) as a natural corrosion inhibitor. The modification process of Sep was carefully monitored and characterized through Zeta potential, scanning electron microscopy, X-ray diffraction, UV/visible spectroscopy, and Fourier transform infrared spectroscopy. The results highlighted the successful clay modification with a silane loading of 7.68 % and a DGE adsorbed amount of approximately 58 mg/g. The DGE release behavior of the elaborated nanocomposite (Sep-G@DGE) was studied at different pH values and showed distinct pH-dependent release profiles. The rates were in the following order: acidic > alkaline > neutral. Electrochemical properties of Sep-G@DGE were investigated on a bare mild steel electrode in 0.1 M NaCl solution, demonstrating a corrosion inhibition efficiency of 90 % for a 24-hour immersion time at a concentration of 1 g/L. Moreover, the beforehand prepared nanocontainer, Sep-G@DGE, was incorporated into an alkyd resin to formulate a smart anti-corrosion coating. This coating exhibited enhanced anti-corrosion properties and sustained inhibitory effects over time compared to that of a pure alkyd coating. The coating's efficiency is attributable to the high dispersion of the layered clay mineral structure, which allowed an on-demand release of the DGE inhibitor. In addition, the presence of free APDEMS NH3+ group leads to the formation of electrostatic interactions with the adsorbed chloride ions on the metal surface, acting thus as a barrier against corrosive agents and inhibit rust formation in paint cracks.