Chemical composition and corrosion protection of silane films modified with CeO2 nanoparticles

CeO2 nanoparticle dose and exposure modulate soybean development and plant-mediated responses in root-associated bacterial communities

Agricultural soils are increasingly undergoing inadvertent and purposeful exposures to engineered CeO2 nanoparticles (NPs), which can impact crops and root-associated microbial communities. However, interactions between NP concentration and exposure duration on plant-mediated responses of root-associated bacterial communities are not well understood. Soybeans seedlings were grown in soil with uncoated NPs added at concentrations of 0, 1 or 100 mg kg-1. Total soil exposure durations were either 190 days, starting 106 days before planting or 84 days with NP amendments coinciding with planting. We assessed plant development, bacterial diversity, differential abundance and inferred functional changes across rhizosphere, rhizoplane, and root tissue compartments. Plant non-monotonic dose responses were mirrored in bacterial communities. Most notably, effects were magnified in the rhizoplane under low-dose, short-exposures. Enriched metabolic pathways were primarily related to biosynthesis and degradation/utilization/assimilation, rather than responses to metals or oxidative stress. Our results indicate that plant-mediated bacterial responses were greater than direct NP impacts. Also, we identify needs for modeling non-monotonic legume stress responses that account for coinfection with mutualistic and parasitic bacteroids. Our findings provide new insights regarding effects of applications of soil amendments such as biosolids containing NPs or nano-enabled formulations used in cultivation of legumes and other crops.

Operando Scanning Electrochemical Probe Microscopy during Electrocatalysis

Scanning electrochemical probe microscopy (SEPM) techniques can disclose the local electrochemical reactivity of interfaces in single-entity and sub-entity studies. Operando SEPM measurements consist of using a SEPM tip to investigate the performance of electrocatalysts, while the reactivity of the interface is simultaneously modulated. This powerful combination can correlate electrochemical activity with changes in surface properties, e.g., topography and structure, as well as provide insight into reaction mechanisms. The focus of this review is to reveal the recent progress in local SEPM measurements of the catalytic activity of a surface toward the reduction and evolution of O₂ and H₂ and electrochemical conversion of CO₂. The capabilities of SEPMs are showcased, and the possibility of coupling other techniques to SEPMs is presented. Emphasis is given to scanning electrochemical microscopy (SECM), scanning ion conductance microscopy (SICM), electrochemical scanning tunneling microscopy (EC-STM), and scanning electrochemical cell microscopy (SECCM).

Improving the Mechanical/Anticorrosive Properties of a Nitrile Rubber-Based Adhesive Filled with Cerium Oxide Nanoparticles Using a Two-Step Surface Modification Method

To prepare a nanocomposite adhesive based on nitrile rubber (NBR) with excellent mechanical/anticorrosion properties, cerium oxide (CeO₂) nanoparticles were grafted with bis-[3-(triethoxysilyl)propyl]tetrasulfide silane (TESPT) at different concentrations (i.e., 1, 5, 10, and 20 times the stoichiometric content). The surface-modified nanoparticles were characterized by Fourier transform infrared spectroscopy (FTIR), ζ-potential, X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and field emission scanning electron microscopy (FE-SEM) techniques. The results showed that the steaming process resulted in an increase in the grafting ratio (R _g) by 2.35 times. Pure and modified cerium oxide nanoparticles were added at 1.5, 4.5, and 7.5 wt % to a mixture of a phenolic resin and NBR compound to prepare adhesive samples. The prepared adhesives were evaluated for curing behavior and thermomechanical properties. The morphology of the adhesives was also characterized using SEM analysis. The bonding of adhesives to steel plates was measured by a cathodic disbonding test. The adhesive-coated steel plates were evaluated for anticorrosion performances using a salt spray test. It was found that surface-modified hydrothermally steamed CeO₂ nanoparticles that had the highest silane grafting ratio enhanced the anticorrosion properties and cathodic disbonding of NBR-based adhesives. The curing rate index (CRI) and crosslinking of the NBR compound were enhanced using the modified and steamed nanoparticles. This also improved the interfacial interactions between rubber chains and nanoparticle surface, resulting in a 6 °C increase in the glass-transition temperature (T _g) of NBR compared to the pristine rubber.

Effect of Organosilicon Self-Assembled Polymeric Nanolayers Formed during Surface Modification by Compositions Based on Organosilanes on the Atmospheric Corrosion of Metals

Reducing the risks caused by losses due to the atmospheric corrosion of metal structures has been relevant for many years and is an important scientific and technical task. Previously, for this purpose, the preliminary modification of the surface of structural metals with solutions of compositions, based on both individual organosilanes and their mixtures with amine-containing corrosion inhibitors, was proposed. Such treatment leads to the formation of self-assembled siloxane polymeric/oligomeric nanoscale layers on the metal surface, which are capable of changing the physicochemical properties of the metal surface (namely, by reducing the tendency of the metal to corrosive destruction). In this work, annual atmospheric corrosion tests of samples of steel, copper, zinc, and aluminum without protection, and samples modified with compositions based on organosilanes in an urban atmosphere, were carried out. It was established (by the gravimetric method) that the corrosion rate of unmodified (without protection) metals is as follows: steel—0.0022 mm/year; aluminum—0.0015 mm/year; copper—0.00018 mm/year; and zinc—0.00023 mm/year. Using gravimetry and optical microscopy, it was shown that the preliminary modification of metal surfaces with compositions based on organosilanes led to the inhibition of both uniform and local corrosion of metals. The corrosion rates of samples that were modified with one-component compositions decreased by almost two times. The maximum inhibitory effect for the studied systems was demonstrated by mixed binary modifying compositions: mixtures of vinyl- and aminosilane, vinylsilane, and benzotriazole. The corrosion rate decreased for all the studied metals. The minimum effect was observed on zinc (2.5 times) and the maximum inhibition of the corrosion rate was obtained on copper (5.1 times). The mechanism of corrosion inhibition by layers formed as a result of surface modification with two-component mixtures was considered.

pH-Sensitive Polydopamine-La (III) Complex Decorated on Carbon Nanofiber toward On-Demand Release Functioning of Epoxy Anti-Corrosion Coating

The high aspect ratio and unique thermal and electrical characteristics of carbon nanofiber (CNF) made it an ideal physical barrier against the penetration of corrosive ions. However, the poor compatibility of the CNF with the polymer matrix and the lack of active corrosion inhibitors are the key limitations of this nanomaterial, resulting in short-term anti-corrosion resistance. An intelligent self-healing epoxy (EP) coating, including CNF modified with a polydopamine (PDA)-La³⁺ complex, was successfully fabricated to overcome these issues. Electrochemical impedance spectroscopy (EIS) evaluation implied that mild steel (MS) submerged in a 3.5 wt % NaCl solution containing the CNF-PDA-La extract had a total corrosion resistance (R_T) of 3107 Ω cm² after 24 h, which is much greater than the MS immersed in the blank solution (1378 Ω cm²). Furthermore, the potentiodynamic polarization analysis indicated a 50% reduction in the corrosion rate (CR) of the MS soaked in the solution containing released PDA and La³⁺ inhibitors compared to the blank solution. EIS and salt spray analysis were used to assess the self-healing capabilities of epoxy coatings incorporating modified CNFs. EIS assessment of scratched coatings revealed a 117% improvement in R_T of the CNF-PDA-La/EP coating compared to the Blank/EP after 10 h of immersion in the saline solution. This enhancement is due to the intelligent release of PDA and La³⁺ inhibitors at the scratch sites, which can mitigate MS corrosion by forming a PDA-Fe complex and the deposition of La(OH)₃ on the MS surface. The salt spray test results also exhibited the CNF-PDA-La/EP coating's superior anti-corrosion capabilities after 20 days. Hence, this research presents a logical approach for developing anti-corrosion coatings with improved nanofiller compatibility and self-healing characteristics.

Preparation and Characterization of Graphene Oxide/Polyaniline/Polydopamine Nanocomposites towards Long-Term Anticorrosive Performance of Epoxy Coatings

To address the challenging issues of metal materials corrosion in industries, which has caused huge economic losses and security threats to many facilities in marine environments, functional polymer coatings have been widely used and regarded as one of the simplest and most effective methods to prevent such an undesirable event. In this study, a new type of coating filler consisting of graphene oxide/polyaniline/polydopamine (GO-PANI-PDA) nanocomposites has been successfully synthesized. The morphology, structure, composition, and corrosion resistance performance of the GO-PANI-PDA (GPP) nanocomposites were investigated via a series of characterization methods. The results from our electrochemical impedance spectroscopy, potentiodynamic polarization curve and salt spray experiment showed that the best corrosion resistance performance of the coating is from GPP 21 with the epoxy/GO-PANI:PDA ratio of 2:1, which exhibited a positive corrosion potential (−0.51 V) shift from epoxy/GO-PANI coating (−0.64 V). The corrosion current density (3.83 × 10−8 A/cm2) of GPP 21 is nearly an order of magnitude lower than that of epoxy/GO-PANI (7.05 × 10−7 A/cm2). The good anti-corrosion performance was fascinatingly observed in salt spray tests even without obvious corrosion phenomenon after 30 days of testing. Due to these remarkable properties, GPP nanocomposites can be an outstanding candidate for the rapid development of broadband shielding and anticorrosive materials.

Experimental and In-Silico Computational Modeling of Cerium Oxide Nanoparticles Functionalized by Gelatin as an Eco-Friendly Anti-Corrosion Barrier on X60 Steel Alloys in Acidic Environments

An eco-friendly and a facile route successfully prepared novel cerium oxide nanoparticles functionalized by gelatin. The introduced CeO₂@gelatin was investigated in terms of FE-SEM, EDX, TEM, chemical mapping, FT-IR, and (TGA) thermal analyses. These characterization tools indicate the successful synthesis of a material having CeO₂ and gelatin as a composite material. The prepared composite CeO₂@gelatin was used as an environment-friendly coated film or X60 steel alloys in acidizing oil well medium. Moreover, the effect of CeO₂ percent on film composition was investigated. LPR corrosion rate, E_ocp-time, EIS, and PDP tools determined the corrosion protection capacity. The CeO₂@gelatin composite exhibited high protection capacity compared to pure gelatin; in particular, 5.0% CeO₂@gelatin coating film shows the highest protection capacity (98.2%), with long-term anti-corrosive features. The % CeO₂@gelatin-coated films formed the protective adsorbed layer on the steel interface by developing a strong bond among nitrogen atoms in the CeO₂@gelatin film and the electrode interface. Surface morphology using FESEM measurements confirmed the high efficiency of the fabricated CeO₂@gelatin composite on the protection X60 steel alloys. DFT calculations and MC simulations were explored to study the relations between the protection action and the molecular construction of the coated systems, which were in good alignment with the empirical findings.

Recent insights into the impact, fate and transport of cerium oxide nanoparticles in the plant-soil continuum

The advent of the nanotechnology era offers a unique opportunity for sustainable agriculture provided that the exposure and toxicity are adequately assessed and properly controlled. The global production and application of cerium oxide nanoparticles (CeO₂-NPs) in various industrial sectors have tremendously increased. Most of the nanoparticles end up in water and soil where they interact with soil microorganisms and plants. Investigating the uptake, translocation and accumulation of CeO₂-NPs is critical for its safe application in agriculture. Plant uptake of CeO₂-NPs may lead to their accumulation in different plant tissues and interference with key metabolic processes of plants. Soil microbes can also be affected by increasing CeO₂-NPs in soil, leading to changes in the physiology and enzymatic activity of soil microorganisms. The interactions between CeO₂-NPs, microbes and plants in the agricultural system need systemic research in ecologically relevant conditions. In the present review, The uptake pathways and in-planta translocation of CeO₂-NPs,and their impact on plant morphology, nutritional values, antioxidant enzymes and molecular determinants are presented. The role of CeO₂-NPs in modifying soil microbial community in plant rhizosphere is also discussed. Overall, the review aims to provide a comprehensive account on the behaviour of CeO₂-NPs in soil-plant systems and their potential impacts on the soil microbial community and plant health.

Ceria Particles as Efficient Dopant in the Electrodeposition of Zn-Co-CeO2 Composite Coatings with Enhanced Corrosion Resistance: The Effect of Current Density and Particle Concentration

Novel Zn-Co-CeO2 protective composite coatings were deposited successfully from chloride plating solutions. Two different types of ceria sources were used and compared: commercial ceria powder and home-made ceria sol. Electrodeposition was performed by a direct current in the range of 1-8 A dm-2. Two different agitation modes were used and compared, magnetic stirring and ultrasound-assisted stirring (US). The influence of magnetic stirring on the stability of the related plating baths was evaluated via a dynamic scattering method. The results pointed to better stability of the prepared ceria sol. The morphology of the composite coatings was examined by scanning electron microscopy (SEM), and particle content was determined by energy-dispersive X-ray spectroscopy (EDS). The results showed that the increase in the deposition current density was not beneficial to the coating morphology and particle content. The corrosion behavior of the Zn-Co-CeO2 composite coatings was analyzed and compared by electrochemical impedance spectroscopy and polarization resistance. The ultrasound-assisted electrodeposition at small current densities was favorable for obtaining composite coatings with enhanced corrosion stability. The protection was more effective when US was applied and, additionally, upon utilization of ceria sol as a particle source, which was revealed by higher polarization resistance and greater low-frequency impedance modulus values for sol-derived composite coatings deposited under ultrasound.

Fabrication of Reproducible and Selective Ammonia Vapor Sensor-Pellet of Polypyrrole/Cerium Oxide Nanocomposite for Prompt Detection at Room Temperature

Polypyrrole (PPy) and polypyrrole/cerium oxide nanocomposite (PPy/CeO₂) were prepared by the chemical oxidative method in an aqueous medium using anhydrous ferric chloride (FeCl₃) as an oxidant. The successful formulation of materials was confirmed by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and transmittance electron microscopy (TEM). A four-in-line probe device was used for studying DC electrical conductivity and ammonia vapor sensing properties of PPy and PPy/CeO₂. The significant improvement in both the conductivity and sensing parameters of PPy/CeO₂ compared to pristine PPy reveals some synergistic/electronic interaction between PPy and cerium oxide nanoparticles (CeO₂ NPs) working at molecular levels. The initial conductivity (i.e., conductivity at room temperature) was found to be 0.152 Scm^-1 and 1.295 Scm^-1 for PPy and PPy/CeO₂, respectively. Also, PPy/CeO₂ showed much better conductivity retention than pristine PPy under both the isothermal and cyclic ageing conditions. Ammonia vapor sensing was carried out at different concentration (0.01, 0.03, 0.05, 0.1, 0.2, 0.3, 0.4, and 0.5 vol %). The sensing response of PPy/CeO₂ varied with varying concentrations. At 0.5 vol % ammonia concentration, the % sensing response of PPy and PPy/CeO₂ sensor was found to be 39.1% and 93.4%, respectively. The sensing efficiency of the PPy/CeO₂ sensor was also evaluated at 0.4. 0.3, 0.2, 0.1, 0.05, 0.03, and 0.01 vol % ammonia concentration in terms of % sensing response, response/recovery time, reversibility, selectivity as well as stability at room temperature.

Zn-Co-CeO2 vs. Zn-Co Coatings: Effect of CeO2 Sol in the Enhancement of the Corrosion Performance of Electrodeposited Composite Coatings

Electrodeposition and characterization of novel ceria-doped Zn-Co composite coatings was the main goal of this research. Electrodeposited composite coatings were compared to pure Zn-Co coatings obtained under the same conditions. The effect of two ceria sources, powder and home-made sol, on the morphology and corrosion resistance of the composite coatings was determined. During the electrodeposition process the plating solution was successfully agitated in an ultrasound bath. The source of the particles was found to influence the stability and dispersity of plating solutions. The application of ceria sol resulted in an increase of the ceria content in the resulting coating and favored the refinement from cauliflower-like morphology (Zn-Co) to uniform and compact coral-like structure (Zn-Co-CeO2 sol). The corrosion resistance of the composite coatings was enhanced compared to bare Zn-Co as evidenced by electrochemical impedance spectroscopy and scanning Kelvin probe results. Zn-Co doped with ceria particles originating from ceria sol exhibited superior corrosion resistance compared to Zn-Co-CeO2 (powder) coatings. The self-healing rate of artificial defect was calculated based on measured Volta potential difference for which Zn-Co-CeO2 (sol) coatings exhibited a self-healing rate of 73.28% in a chloride-rich environment.

The Rapeseed Oil Based Organofunctional Silane for Stainless Steel Protective Coatings

The earlier obtained organosilicon derivatives of rapeseed oil were used for the production of coatings protecting steel surface against corrosion. Vegetable oils have been hitherto used for temporary protection of metals against corrosion, while thanks to the synthesis of appropriate organosilicon derivatives, it is now possible to create durable protective coatings. Due to the presence of alkoxysilyl groups and the use of the sol-gel process, the coatings obtained were bonded to the steel surface. The effectiveness of the coatings was checked by electrochemical methods and steel surface analysis.

Corrosion Protection of A36 Steel with SnO2 Nanoparticles Integrated into SiO2 Coatings

Tin oxide (SnO2) nanoparticles were successfully added to silicon oxide (SiO2) coatings deposited on A36 steel by the sol-gel and dip-coating methods. These coatings were developed to improve the performance of corrosion protection of steel in a 3 wt % NaCl solution. The effects of modifying the SnO2 particle concentration from 0–7.5 vol % were investigated by polarization resistance, Tafel linear polarization, and electrochemical impedance spectroscopy (EIS). The formation of protective barriers and their corrosion inhibition abilities were demonstrated. It was found by electrochemical studies that all of the coated samples presented higher corrosion resistances compared with an uncoated sample, indicating a generally beneficial effect from the incorporation of the nanoparticles. Furthermore, it was established that the relationship between the SnO2 content and the corrosion inhibition had parabolic behaviour, with an optimum SnO2 concentration of 2.5 vol %. EIS showed that the modified coatings improved barrier properties. The resistance for all of the samples was increased compared with the bare steel. The corrosion rate measurements highlighted the corrosion inhibition effect of SnO2 nanoparticles, and the Tafel polarization curves demonstrated a decrease in system dissolution reactions at the optimal nanoparticle concentration.

Microbiologically influenced corrosion mechanism of 304L stainless steel in treated urban wastewater and protective effect of silane-TiO2 coating

Microbiologically influenced corrosion (MIC) of bare and silane-TiO₂ sol-gel coated stainless steel (SS) was studied in treated urban wastewater (TUWW). Combining the electrochemical impedance spectroscopy (EIS) and the scanning vibrating electrode technique (SVET) showed that SS surface colonization occurs, at earlier stages, by iron-oxidizing bacteria (IOB), and later by sulphate-reducing bacteria (SRB). The SVET results showed that chemical corrosion process and bacterial respiration led to the depletion of dissolved oxygen, creating a differential aeration cell and thus a localized corrosion phenomenon. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) showed that the growth of a bacterial biofilm on 304L SS was a dynamic process, stimulating the localized oxidation of SS. To improve corrosion protection, a silane-TiO₂ sol-gel coating for SS is proposed. SEM showed that the coating reduced bacterial adhesion and EIS study demonstrated that the coating improved the barrier properties and corrosion resistance of 304L SS in TUWW over a short period of immersion.

Self-Protecting Epoxy Coatings with Anticorrosion Microcapsules

The corrosion of steel substrates causes damage that is costly to repair or replace. Current protective coatings predominately rely on environmentally harmful anticorrosive agents and toxic solvents to protect the underlying substrate. The use of lawsone (2-hydroxy-1,4-napthoquinone) together with a water-based epoxy coating provides an environmentally friendly alternative for common protective coatings. Microencapsulated lawsone embedded in an epoxy coating allows the anticorrosive agent to remain dormant until released by damage and delivered directly onto the steel substrate. UV-vis analysis confirms successful encapsulation of lawsone in a polyurethane shell wall and reveals up to 8 wt % lawsone in the capsule cores. Uniform dry film thickness and inflicted damaged are verified with ultrasound and optical microscopy. Visual and electrochemical analysis demonstrates that this self-protective scheme leads to a 70% corrosion inhibition efficiency in a neutral salt water solution.

Enhanced Optical Properties of ZnO and CeO2-coated ZnO Nanostructures Achieved Via Spherical Nanoshells Growth On A Polystyrene Template

In this paper, ZnO, CeO₂ and CeO₂-coated ZnO nanostructures were synthesised by simple and efficient low temperature wet chemical methods on Si (100) and quartz substrates. The ZnO films were prepared by a drop coating deposition method. This was then combined with a thin layer of the redox active material CeO₂ to form CeO₂-coated ZnO films. Spherical ZnO nanoshell structures and CeO₂-coated ZnO nanoshells have been prepared using polystyrene (PS) sphere monolayer templates. The structural properties and morphologies of the nanostructures were analysed by x-ray diffraction (XRD) and scanning electron microscopy (SEM). The nanostructure compositions are studied in more detail using secondary ion mass spectroscopy (SIMS). The optical properties of the nanostructures were measured using ultraviolet-visible (UV-Vis) absorption spectroscopy in order to ascertain the effects of the nanoshell structures and the whispering gallery modes associated with these structures on the optical properties of the deposits. Our data show UV and visible light absorption was very significantly enhanced due to this nanostructuring.

A review on the application of inorganic nanoparticles in chemical surface coatings on metallic substrates

Nanocomposite coatings obtained by the controlled addition of inorganic nanoparticles into the treatment baths not only improve the corrosion resistance and mechanical properties, but also enhance the functional properties.

Excellent anti-corrosive pretreatment layer on iron substrate based on three-dimensional porous phytic acid/silane hybrid

A novel, highly effective and environmentally friendly film-forming material, phytic acid (PA)/silane (denoted as PAS) hybrid with a three-dimensional (3D) network structure, was prepared through a condensation reaction of PA with methyltrihydroxysilane generated from the hydrolysis of methyltriethoxysilane (MTES). Two kinds of PAS-based pretreatment layers, namely NaBrO3-free and NaBrO3-doped PAS layers, were fabricated on iron substrates using the dip-coating method. SEM and AFM observations showed that the as-fabricated PAS-based layers possessed a 3D porous microstructure at the nanoscale and a rough surface morphology. X-ray photoelectron spectroscopic (XPS) and attenuated total reflection infrared (ATR-IR) spectroscopic characterization demonstrated that the above PAS layers bound to the iron surface via the -P-O- bond. Moreover, analyses of steady-state polarization curves and electrochemical impedance spectroscopic (EIS) data indicated that the corrosion rates of the iron substrates decreased considerably in the presence of the two PAS-based pretreatment layers. In particular, the NaBrO3-dosed PAS layer displayed the better corrosion resistance ability as well as maintaining the original microstructure and surface morphology. The PAS-based pretreatment layers are expected to act as substitutes for chromate and phosphate conversion layers and will find widespread application in the surface pretreatment of iron and steel materials due to the advantages of being environmentally friendly, the rapid film-forming process, and, especially, the nanoporous microstructure and rough surface morphology.

Application of ordered mesoporous silica nanocontainers in an anticorrosive epoxy coating on a magnesium alloy surface

Epoxy coatings containing inhibitor loaded silica nanocontainers were applied to Mg alloy. When damage was caused in coatings during immersion time, the coatings displayed self-healing property with the release of inhibitor from nanocontainers.

Influence of Zeolite Coating on the Corrosion Resistance of AZ91D Magnesium Alloy

The protective performance of zeolite coating on AZ91D magnesium alloy was evaluated using potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS) in 0.1 M sodium chloride solution (NaCl). Electrical equivalent circuit (EEC) was developed based upon hypothetical corrosion mechanisms and simulated to correspond to the experimental data. The morphology and the chemical nature of the coating were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. Post corrosion morphologies of the zeolite coated and the uncoated AZ91D alloy were investigated using SEM. The corrosion resistance of the zeolite coated specimen was at least one order of magnitude higher than the uncoated specimen.

Band gap engineering of CeO2 nanostructure using an electrochemically active biofilm for visible light applications

An electrochemically active biofilm was utilized for modification of CeO₂ nanostructures.