Potential use of smart coatings for corrosion protection of metals and alloys: A review

Corrosion inhibition ability of L-tryptophan and 5-hydroxy-L-tryptophan for mild steel: a combination of experimental and theoretical methods

An investigation into the corrosion inhibition properties of L-tryptophan (TP) and 5-hydroxy-L-tryptophan (5-OH-TP) for mild steel in a 1.0 M HCl acidic medium was conducted using experimental and theoretical methods. Results obtained from polarization curve measurements reveal that TP and 5-OH-TP are effective mixed-type inhibitors, exhibiting the highest inhibition efficiencies of 91.22% and 94.05%, respectively, at a temperature of 293 K and a concentration of 10-2 M. However, their inhibition efficiencies gradually decline with increasing temperature, reaching the lowest values of 70.65% for TP and 73.55% for 5-OH-TP at a concentration of 10-4 M and a temperature of 323 K. The adsorption of TP and 5-OH-TP on the steel surface follows the Langmuir isotherm, suggesting monolayer adsorption. Electrochemical impedance spectroscopy analysis indicates that the adsorbed inhibitors form a protective film, effectively shielding the steel from corrosive agents in the solution. Notably, 5-OH-TP consistently exhibits superior inhibition efficiency compared to TP, attributed to the presence of polar OH groups that facilitate stronger bonding of the inhibitor molecule with the metal surface. Quantum chemical parameters and molecular dynamics simulations further confirm the superior corrosion inhibition ability of 5-OH-TP over TP in acidic environments. In particular, the binding energies of protonated TP at the N3 position and 5-OH-TP at the N4 position are 556.40 and 579.27 kJ mol-1, respectively.

Dual Stimulus Responsive GO-Modified Tb-MOF toward a Smart Coating for Corrosion Detection

Smart-sensing coatings that exhibit multistimulus response, rapid indication, and reusability are in urgent need to effectively enhance the practicability of coatings while accurately detecting metal corrosion. In this work, a reusable corrosion self-reporting coating with multiple pH and Fe3+ stimulus responses was first constructed by the integration of a composite fluorescent probe into the resin matrix. This composite sensor was constructed by combining a lanthanide metal-organic framework (Ln-MOF) based on terbium and trimeric acid (H3BTC) with graphene oxide (GO) nanosheets (GO@Tb-BTC). The incorporation of GO formed a sea-urchin-like structure, thereby increasing the specific surface area and active sites of the probe. The coatings were characterized by using electrochemical impedance spectroscopy (EIS), visual observation, and fluorescence spectrophotometry. The surface morphology, wettability, and adhesion of the coating samples were analyzed using SEM, XPS, hydrostatic contact angle test, and an adhesion test. EIS measurements in 3.5 wt % NaCl solution for 72 h demonstrated the superior corrosion protection performance of the 0.3 wt %/GO@Tb-BTC/WEP coating compared to blank coating, with the charge-transfer resistance reaching 4.33 × 107 Ω·cm2, which was 9.5 times higher than that of the pure coating. The bright green fluorescence of GO@Tb-BTC/WEP coating exhibited a turn-off response when there was an excess of OH-/H+, but it demonstrated a reversible turn-on fluorescence when the ambient pH returned to neutral. Furthermore, such Fe3+-triggered fluorescence quenching responded to concentrations as low as 1 × 10-6 M. The fluorescence quenching rate of both intact and damaged coatings surpassed that of visual and EIS detection methods. Significantly, the fluorescence in scratches was effectively quenched within 25 min using 0.3 wt %/GO@Tb-BTC/WPU coating for visual observation. GO@Tb-BTC demonstrated exceptional corrosion self-reporting capabilities in both epoxy and polyurethane systems, making it a versatile option beyond single-coating applications.

Corrosion-Responsive Self-Healing Coatings

Organic coatings are one of the most popular and powerful strategies for protecting metals against corrosion. They can be applied in different ways, such as by dipping, spraying, electrophoresis, casting, painting, or flow coating. They offer great flexibility of material designs and cost effectiveness. Moreover, self-healing has evolved as a new research topic for protective organic coatings in the last two decades. Responsive materials play a crucial role in this new research field. However, for targeting the development of high-performance self-healing coatings for corrosion protection, it is not sufficient just to focus on smart responsive materials and suitable active agents for self-healing. A better understanding of how coatings can react on different stimuli induced by corrosion, how these stimuli can spread in the coating, and how the released agents can reach the corroding defect is also of high importance. Such knowledge would allow the design of coatings that are optimized for specific applications. Herein, the requirements and possibilities from the corrosion and synthesis perspectives for designing materials for preparing self-healing coatings for corrosion protection are discussed.

Investigation of olive leaf extract as a potential environmentally-friendly corrosion inhibitor for carbon steel

Corrosion constitutes a significant issue in industries that handle metals. Corrosion inhibitors with a low impact on the environment provide a significant economic benefit in various engineering applications. In this work, the effectiveness of olive leaves extract is evaluated as a cost-effective and environmentally-friendly corrosion inhibitor. The corrosion of carbon steel in different concentrations of hydrochloric acid (0.1, 1.0, and 2.0 M) when protected by an aqueous solution of olive leaf extract of concentrations ranging from 10 to 60 ppm is investigated. A green extraction process based upon water extraction is used to ensure minimum impact on the environment. Results show that the corrosion inhibition efficiency increased as the concentration of the olive leaf extract increased. An analysis of variance showed a significant effect of acidic molarity, temperature, and inhibitor concentration on the corrosion rate. A significant statistical model indicates that the inhibitor exhibits higher efficiencies at higher acidic molarity. Results of SEM and EDX also demonstrated that a protective film of the inhibitor on the specimen surface plays a role in corrosion inhibition, suggesting that the inhibitor molecules are adsorbed at the interface between the carbon steel and the acid solution. The study provides an insight on the corrosion mechanism and highlights the potential of olive oil extract as an eco-friendly alternative to traditional corrosion inhibitors.

Multilayered LDH/Microcapsule Smart Epoxy Coating for Corrosion Protection

A multilayered smart epoxy coating for corrosion prevention of carbon steel was developed and characterized. Toward this direction, as a first step, zinc-aluminum nitrate-layered double hydroxide (Zn/Al LDH) was synthesized using the hydrothermal crystallization technique and then loaded with dodecylamine (DOD), which was used as an inhibitor (pH-sensitive). Similarly, the synthesis of the urea-formaldehyde microcapsules (UFMCs) has been carried out using the in-situ polymerization method, and then the microcapsules (LAUFCs) were encapsulated with linalyl acetate (LA) as a self-healing agent. Finally, the loaded Zn/Al LDH (3 wt %) and modified LAUFCs (5 wt %) were reinforced into an epoxy matrix to develop a double-layer coating (DL-EP). For an exact comparison, pre-layer epoxy coatings comprising 3 wt % of the loaded Zn/Al LDH (referred to as LDH-EP), top-layer epoxy coatings comprising 5 wt % linalyl acetate urea-formaldehyde microcapsules (referred to as UFMLA COAT), and a blank epoxy coating (reference coating) were also developed. The developed epoxy coatings were characterized using various techniques such as XRD, XPS, BET, TGA, FTIR, EIS, etc. Electrochemical tests performed on the synthesized coatings indicate that the DL-EP demonstrates improved self-healing properties compared to LDH-EP and UFMLA COAT.

Environment-Induced Degradation of Shape Memory Alloys: Role of Alloying and Nature of Environment

Shape memory effects coupled with superelasticity are the distinctive characteristics of shape memory alloys (SMAs), a type of metal. When these alloys are subject to thermomechanical processing, they have the inherent ability to react to stimuli, such as heat. As a result, these alloys have established their usefulness in a variety of fields and have in recent years been chosen for use in stents, sensors, actuators, and several other forms of life-saving medical equipment. When it comes to the shape memory materials, nickel-titanium (Ni-Ti) alloys are in the forefront and have been chosen for use in a spectrum of demanding applications. As shape memory alloys (SMAs) are chosen for use in critical environments, such as blood streams (arteries and veins), orthodontic applications, orthopedic implants, and high temperature surroundings, such as actuators in aircraft engines, the phenomenon of environment-induced degradation is of both interest and concern. Hence, the environment-induced degradation behavior of the shape memory alloys (SMAs) needs to be studied to find viable ways to improve their resistance to an aggressive environment. The degradation that occurs upon exposure to an aggressive environment is often referred to as corrosion. Environment-induced degradation, or corrosion, being an unavoidable factor, certain techniques can be used for the purpose of enhancing the degradation resistance of shape memory alloys (SMAs). In this paper, we present and discuss the specific role of microstructure and contribution of environment to the degradation behavior of shape memory alloys (SMAs) while concurrently providing methods to resist both the development and growth of the degradation caused by the environment.

Encapsulated Corrosion Inhibitive Pigment for Smart Epoxy Coating Development: An Investigation of Leaching Behavior of Inhibitive Ions

A comparative study between the leaching behavior of inhibitive ions from conventionally pigmented and smart (with encapsulated pigments) epoxy coatings has been conducted. Leaching of calcium phosphate as an inhibitive pigment from epoxy coatings was tested in 3.5 wt % NaCl solution. The results showed that pigment encapsulation contributed to a more uniform and stable coating microstructure based on the Scanning Electron Microscopy-Energy-Dispersive X-ray Spectroscopy (SEM-EDX) analysis and a higher leaching rate of the inhibitive pigment via the Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) analysis, thereby enhancing both the active corrosion protection and the barrier properties of the coating film. This was further verified by the Electrochemical Impedance Spectroscopy (EIS) measurements. After 7 days of immersion in 3.5 wt % NaCl solution, the coating resistance of the smart epoxy coating with mesoporous silica nanoparticle encapsulated calcium phosphate (MSN-CP3%) was 2 × 10⁹ Ω·cm² compared to 1.1 × 10⁶ Ω·cm² and 2.6 × 10⁶ Ω·cm² for the conventional epoxy coatings pigmented with 3 wt % and 5 wt % calcium phosphate (CP3% and CP5%), respectively.

High linoleic waste sunflower oil: A distinctive recycled source of self-healing agent for smart metal coatings

High Linoleic Waste Sunflower Oil (HLWSO) is a new self-healing agent viable to be encapsulated. Meanwhile, the unique mechanism behind the synthesis of microcapsules is deeply illustrated; the emulsification process of HLWSO by anionic surfactant and microencapsulation of HLWSO. In addition, the application of microencapsulated HLWSO in the coating matrix by the layering method is presented followed by a detailed explanation of the self-healing mechanism of a smart coating incorporating the polymerization mechanism of HLWSO developed by the diene structure. Microencapsulation of high linoleic waste sunflower oil (HLWSO) is a wall formation process in which urea-formaldehyde (UF) is attached with emulsified HLWSO to form a microcapsule. In this study, the HLWSO from recycled cooking oil is uniquely bonded with a diene structure, thus possessing the ability to dry fast and be encapsulated via the in-situ polymerization method. The microencapsulated HLWSO was characterized using Field Emission Scanning Electron Microscopy (FESEM) and Fourier Transformation Infra-Red Spectroscopy (FTIR). The optimum microcapsules synthesized from HLWSO resulted in a smooth shell structure with 2.88 μm diameter microcapsules at 0.31 μm shell thickness and 66% core content. It was demonstrated that increased stirring speed decreases the size, shell thickness, and core content of the microcapsules. The FTIR results indicated that HLWSO as a core, while urea-formaldehyde acted as a shell of microcapsules. The scratch on the coating matrix embedded with HLWSO was healed after five days. The corrosion rate of optimum sample was 0.0574 mm/year, with an optimum reduction of 58% from the reference sample. This study revealed that the HLWSO from recycled sources is a viable self-healing agent to be microencapsulated. The smart coating embedded with HLWSO also displayed self-healing performance, reduced corrosion rate and beneficial for the advancement of corrosion control technology.

Surface protection against corrosion of Ni turbine blades by electrophoretic deposition of MnO2, TiO2 and TiO2-C nanocoating

The turbine blades of turbochargers are corroded after being cleaned with water in the presence of gasses produced during the combustion of heavy fuel. For that, manganese oxide (MnO₂), titanium dioxide (TiO₂), and titanium oxide-graphene (TiO₂-C) nanomaterials have been coated on the nickel alloy, which is the composition of turbine blades, by the electrophoretic deposition technique for protection against the corrosion process. The anticorrosion performance of nanomaterial coatings has been investigated using electrochemical methods such as open circuit potential, potentiodynamic, electrochemical impedance, and linear polarization resistance in a 1 M H₂SO₄ solution saturated with carbon dioxide. The corrosion rate of nanomaterial-coated Ni-alloy was lower than bare alloy, and potential corrosion increased from -0.486 V for uncoated Ni-alloy to -0.252 V versus saturated calomel electrode for nanomaterial coated Ni-alloy electrodes. Electrochemical measurements show that TiO₂ coated Ni-alloy corrosion has good protective qualities, with an efficiency of 99.91% at 0.146 mA cm² current density in sulfuric acid media. The findings of this study clearly show that TiO₂ has a high potential to prevent nickel alloy turbine blades from corrosion in acidic media. Furthermore, the surface morphologies have revealed that TiO₂ and MnO₂ coatings might successfully block an acid assault due to the high adhesion of the protective layer on the nickel alloy surface. The use of X-ray diffraction (XRD) enhanced the various measures used to determine and study the composition of the alloy surface's protective coating.

Corrosion in seawater desalination industry: A critical analysis of impacts and mitigation strategies

In the current world, freshwater production by clean energy sources with minimum environmental footprints is the main challenge for humankind which is dramatically deteriorating by overexploitation of available water resources. Seawater desalination technology greatly contributes to the mitigation of these serious conditions to produce potable water. However, because desalination plants handle extremely aggressive seawater under stringent operational conditions, they are highly vulnerable to insidious effects of corrosion primarily in the form of general and localized corrosion. Moreover, mineral scaling and bio-fouling are major challenges that further exacerbate corrosion phenomena. So, to ensure the continual operation and curbing corrosion in seawater desalination systems, strict monitoring and selection of highly corrosion-resistance materials are of prime concern. The present paper briefly explores fundamental concepts of corrosion in the desalination industry besides discussing different mitigation strategies for reducing the pernicious effects of corrosion which gravely impair environment quality and durability of desalination infrastructures. Moreover, the authors propose the knowledge gaps and perspectives to delineate the future research direction. Effective solutions for avoiding seawater stagnation, developing highly sophisticated coatings and surface modification technologies, application of advanced computational programs for accurate prediction of possible corrosion failure in desalination plants, and using quantum technology and magnetic corrosion inhibitor in seawater desalination are recommended as an urgent future research focus to combat against corrosion. On the whole, despite outstanding breakthroughs in the field of corrosion control in the desalination industry, the long-term performance of current materials is highly controversial as still many cases of corrosion failures have been reported which indicates the necessity of intensive research work.

Waterborne Eco-Sustainable Sol-Gel Coatings Based on Phytic Acid Intercalated Graphene Oxide for Corrosion Protection of Metallic Surfaces

In the past few years, corrosion protection of metal materials has become a global challenge, due to its great economic importance. For this reason, various methods have been developed to inhibit the corrosion process, such as surface treatment approaches, by employing corrosion inhibitors through the deposition of opportunely designed functional coatings, employed to preserve from corrosion damages metallic substrates. Recently, among these techniques and in order to avoid the toxic chromate-based pre-treatment coatings, silane-based coatings and films loaded with organic and inorganic corrosion inhibitors have been widely used in corrosion mitigation water-based surface treatment. In this study, the synthetic approach was devoted to create an embedded, hosted, waterborne, and eco-friendly matrix, obtained by use of the sol–gel technique, through the reaction of functional alkoxysilane cross-linking precursors, namely (3-glycidyloxypropyl)trimethoxysilane (GPTMS) and (3-aminopropyl)triethoxysilane (APTES), in the presence of graphene oxide (GO) intercalated with natural and non-toxic phytic acid (PA) molecules. As a matter of fact, all experimental results from FT-IR spectroscopy, UV–Vis analysis, and SEM confirmed that PA molecules were successfully decorated on GO. Furthermore, polarization measurements and a neutral salt spray test were used to evaluate the anticorrosive performance on aluminum and steel substrates, thus showing that the GO-PA nanofiller improved the barrier and corrosion protection properties of the developed functional silane-based coatings.

Expired Cefalexin Loaded into Mesoporous Nanosilica for Self-Healing Epoxy Coating on 304 Stainless Steel

A self-healing epoxy coating is creatively prepared by employing expired cefalexin loaded into mesoporous silica nanomaterials (MSNs) for corrosion protection of 304 stainless steel (304SS). A series of physical characterizations, including transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectrometer, and N₂ adsorption–desorption isotherms, verified that the cefalexin successfully filled porous MSN. The corrosion resistance of the epoxy (EP) coating incorporated with the cefalexin@MSNs is investigated using a Tafel polarization curve and electrochemical impedance spectra (EIS) in a 3.5 wt.% NaCl solution. It is found that the EP-Cefalexin@MSNs coating has a higher self-corrosion voltage and a lower self-corrosion current density than EP coating. Moreover, the charge transfer resistance (R_ct) value of Cefalexin@MSNs coating is twice that of EP coating after immersion for 24 h, indicating that the cefalexin@MSNs significantly enhance the corrosion resistance of the coating under long-duration immersion. The improved corrosion resistance is attributed to the densified adsorption of the cefalexin inhibiting the cathode corrosion reaction, providing a self-healing long-duration corrosion protection for 304SS.

Rising of MXenes: Novel 2D-functionalized nanomaterials as a new milestone in corrosion science - a critical review

Corrosion is a natural process between a metal and its environment that can gradually cause catastrophic damage to the metal equipment, which would have economic implications. Consequently, several protective methods have been utilized to prevent metals from severe degradation. Organic polymeric coatings have been widely used as the most convenient and cost-effective method to boost metals' anti-corrosion properties. Nonetheless, these coatings have a significant amount of solvent, resulting in shrinkage and micro defects in the films during the curing process. Many studies have verified that transition metal carbides/nitrides (MXenes) can form a "labyrinth effect" in the polymeric coatings due to their "nano-barrier effect". Furthermore, based on their sheet-like structures, they can considerably cover the surface defects of the polymeric films. Therefore, the penetration of corrosive elements can be substantially curbed. It is the first review that specifically focused on the new family of 2D nanomaterials, i.e., MXenes, and discussed their applications in corrosion protection systems. The MXenes' pros and cons in the polymeric matrixes as nanofillers will be clarified. Moreover, the synthesis and functionalization methods of the MXenes, their applications, and corrosion protection mechanism will be explored. Subsequently, the MXenes' superiority over other 2D nanomaterials will be highlighted while their future perspectives and industrial applications will be predicted.

Preparation and CMAS Wettability Investigation of CMAS Corrosion Resistant Protective Layer with Micro-Nano Double Scale Structure

Solution precursor plasma spray (SPPS) can prepare thermal barrier coatings (TBCs) with nanostructures, which can modify the adhesion and wettability of molten silicate environmental deposits (CMAS) on the surface of TBCs, thereby improving the resistance of TBCs to CMAS corrosion. In this study, SPPS layers with micro-nano double scale structures were prepared on the surface of conventional atmospheric plasma spraying (APS) coatings. The effect of process parameters on the micro-nano double scale structures and the wetting and infiltration behavior of molten CMAS on the surface of coatings were investigated. The results show that micron structure is more sensitive to process parameters. Lower precursor viscosity, closer spraying distance, and smoother APS layer are favorable to form more typical and dense micron structures. After covering the SPPS layer, the CMAS wetting diameter is reduced by about 40% and the steady-state contact angle increased up to three times. The reason is that the micro-nano double scale structures can effectively trap air and form an air layer between the coating surface and the molten CMAS. In addition, nano-particles play a more important role in the formation of the air layer, which in turn determines the steady-state wettability properties. While micron structures can influence the time needed to reach the steady state. However, the SPPS layers composed of nano-particles have a very loose structure and weak cohesion, and they degrade and fail rapidly after the infiltration of molten CMAS. Therefore, maintaining the excellent CMAS wetting resistance of the SPPS layers while taking into account their lifetime and reliability has become the focus of further research.

A Review of In-Service Coating Health Monitoring Technologies: Towards “Smart” Neural-Like Networks for Condition-Based Preventive Maintenance

In line with the recent industrial trends of hyperconnectivity, 5G technology deployment, the Internet of Things (IoT) and Industry 4.0, the ultimate goal of corrosion prevention is the invention of smart coatings that are able to assess their own condition, predict the onset of corrosion and alert users just before it happens. It is of particular interest to tackle corrosion that occurs in non-accessible areas where human inspectors or handheld devices are useless. To accomplish this, a variety of technologies that are embedded or could potentially be embedded into the coatings are being developed to monitor coating condition, which are based, for instance, on the evolution of electrochemical or mechanical properties over time. For these technologies to be fully embedded into the coatings and work remotely, solutions are needed for connectivity and power supply. A paradigm shift from routine prescheduled maintenance to condition-based preventive maintenance could then become a reality. In this work, the technologies that enable the in-service monitoring of organic anticorrosion coatings were compiled. Soon, some of them could be integrated into the sensing elements of autonomous, connected neural-like networks that are capable of remotely assessing the condition of the anticorrosion protection of future infrastructures.

Review of Cr-Free Coatings for the Corrosion Protection of Aluminum Aerospace Alloys

Aluminum alloys are known to have many advantages (e.g., light weight and low cost) but they are not immune to corrosion. So, it is important to assess their corrosion behavior, in particular under atmospheric conditions. To protect aluminum alloys against corrosion, paints are generally applied onto the materials. Corrosion protection in the aerospace industry consists of a conversion or anodized coating, an inhibited primer, and a top-coat. Chromate conversion coating (CCC) and primers containing chromate pigments have been widely used in the aerospace industry over the last decades. However, new environmental regulations have led to major changes for aluminum corrosion protection. By limiting or prohibiting some chemicals, for instance Cr(VI), the European regulation REACH (Regulation on Registration Evaluation, Authorization and Restriction of Chemicals) has induced major changes to some of the finishing processes of aluminum alloys (e.g., chromate conversion, chromic acid anodizing, and chromate sealing). Interesting results have been obtained while seeking replacements for Cr(VI), for example, with the incorporation of cerium, lithium salt, or nanocontainers loaded with corrosion inhibitors in organic coatings. For several years, hybrid sol–gel coatings able to replace the pre-treatment and primer steps have been under development, showing interesting results. New prospects for the future involve the use of photopolymerization to reduce the energy-intensive heat treatment needed in sol–gel technology. It will also be necessary to test these new technologies in service conditions or in accelerated corrosion tests before being able to conclude on the real effectiveness of these coatings. This review summarizes the recent developments in Cr-free coatings for aluminum alloys. Their advantages and drawbacks are also discussed.

Effectiveness of Some Novel Ionic Liquids on Mild Steel Corrosion Protection in Acidic Environment: Experimental and Theoretical Inspections

Three ionic liquids (ILs)-1-butyl-1-methyl-pyrrolidinium Imidazolate (BMPyrIM), 1-butyl-3-methyl-imidazolium Imidazolate (BMImIM), and bis(1-butyl-3-methyl-imidazolium Imidazolate) (BBMImIM)-were synthesized and examined experimentally and theoretically as potential inhibitors for mild steel corrosion in HCl (1.0 M) solution. To our knowledge, two of the ILs successfully synthesized in our laboratory named BMPyrIM and BBMImIM are novel. Different electrochemical (potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS)), surface and structural (scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS), Atomic force microscopy (AFM) and Fourier Transform Infrared Spectroscopy (FTIR)) and theoretical (Density functional theory (DFT)) techniques were utilized to confirm their use as efficient environmentally safe inhibitors. These ionic liquids were designed to study the cation effect (imidazolium and pyrrolidinium) and the dimeric effect of the imidazolium-based IL. A pronounced inhibiting effect was recorded using the optimum concentration (5 × 10^-3 M) of BBMImIM with protection efficiency of 98.6% compared to 94.3% and 92.4% for BMImIM and BMPyrIM, respectively. The investigated ILs act as a mixed-type corrosion inhibitors and their protection obeys Langmuir adsorption isotherm. The results obtained by SEM, EDS and AFM confirmed the mild steel protection by the formation of protective film of the ILs on the steel surface resulted in less damaged surfaces compared with the blank solution. Furthermore, quantum chemical calculations illustrated the electronic structure of the investigated ILs and their optimized adsorptiοn configurations on mild steel surface. The findings from the different techniques helped to provide a supported interpretation of the inhibition mechanism.

Incorporation of SiO2 functionalized gC3N4 sheets with TiO2 nanoparticles to enhance the anticorrosion performance of metal specimens in aggressive Cl- environment

Nowadays, carbon-based nano-structured materials are widely preferred for composite coating as anti-corrosive reinforcement mainly due to its enhanced physical, chemical and mechanical properties. Herein we develop highly efficient Graphitic carbon nitride-Silica-Titania (gC₃N₄/SiO₂/TiO₂) ternary nanocomposite are synthesized and it is used as a nanofillers in the corrosive protection layer on the proposed metal specimen (i.e., mild steel specimen) in an aggressive chloride environment. Size, structural and morphological analysis were analysed for the confirmation of presence of particles. gC₃N₄ is currently earning quite drastic attention, owing to its affordable cost compared to carbon nanotubes and other carbon-based materials, when gC₃N₄ incorporated with SiO₂ and TiO₂, the composite matrix greatly improves the mechanical strength of the coating mixture. XRD, XPS, EDS analysis projects excellent formation and presence of the ternary nanocomposites. The particles are well-dispersed in epoxy and organic resin and deposited on the mildsteel panels and it is examined using various surface and structural characterization techniques. The obtained results are very encouraging and the ternary composite coatings can be recommended for real world applications.

Influence of the Operating Conditions on the Release of Corrosion Inhibitors from Spray-Dried Carboxymethylcellulose Microspheres

Sodium carboxymethylcellulose (CMC-Na) microparticles, containing corrosion inhibitor benzotriazole (BTA), were prepared using different spray drying processing parameters, with the purpose of future application in protective coatings for the delivery of corrosion inhibitors. The effects of the processing parameters, such as inlet temperature and spray flow rate, are discussed herein. The biopolymeric CMC-Na microparticles obtained were characterized morphologically by SEM and TEM, and their release profile studied by UV-Vis. The results show that the prepared microparticles (microspheres) were homogeneous, spherically shaped and of a matrix-type nature. Additionally, it was observed that the inlet temperature and spray flow rate significantly influenced the release profiles and process yields. From the different process parameters tested, it was found that the best conditions to achieve higher process yields, higher encapsulation efficiencies and better release properties, were an inlet temperature of 170 °C, a pump rate of 2.5 mL/min, and a drying air-flow rate of 440 L/h.

Anti-Corrosion Mechanism of Parsley Extract and Synergistic Iodide as Novel Corrosion Inhibitors for Carbon Steel-Q235 in Acidic Medium by Electrochemical, XPS and DFT Methods

The parsley extract (PLE) was prepared using absolute ethyl alcohol. The PLE and synergistic iodide were firstly utilized as efficacious corrosion inhibitors to slow down the corrosion rate of carbon steel-Q235 in 0.5 mol/L H₂SO₄ solution. The anti-corrosion performance was researched by weight loss method, electrochemical tests, surface analysis and quantum chemistry calculation. Results of electrochemical and weight loss tests show that the synergetic PLE and I⁻ exhibit the optimal corrosion inhibition efficiency 99%. The combined inhibitor displays the favorable long-term corrosion inhibition effect, and the inhibition efficiency can maintain more than 90% after 144 h immersion. The introduction of I⁻ makes carbon steel surface with higher negative charge amount, which could be beneficial to the interaction between corrosion inhibitor and Fe atoms. The adsorption behavior obeys the Langmuir isotherm adsorption, and involves chemical and physical adsorption. On the basis of electrochemical consequences and theoretical calculation, the adsorption process and anti-corrosion mechanisms are further explored.

Ionic liquid-based antimicrobial materials for water treatment, air filtration, food packaging and anticorrosion coatings

Efforts to widen the scope of ionic liquids applications across diverse research areas have flourished in the last two decades with developments in understanding and tailoring their physical, chemical, and biological properties. The promising applications of ionic liquids-based materials as antimicrobial systems is due to their ability and flexibility to be tailored in varying sizes, morphologies, and surface charges. Ionic liquids are also considered as greener materials. Common methods for the preparation of ionic liquid-based materials include crosslinking, loading, grafting, and combination of ionic liquids with other polymeric materials. Recent research focuses on the tuning of the biological properties to design novel ionic liquids-based antimicrobial materials. Here, the properties, synthesis and applications of ionic liquids and ionic liquids-based materials are reviewed with focus on antimicrobial activities applied to water treatment, air filtration, food packaging, and anticorrosion.

Atomic-Scale Layer-by-Layer Deposition of FeSiAl@ZnO@Al2O3 Hybrid with Threshold Anti-Corrosion and Ultra-High Microwave Absorption Properties in Low-Frequency Bands

Developing highly efficient magnetic microwave absorbers (MAs) is crucial, and yet challenging for anti-corrosion properties in extremely humid and salt-induced foggy environments. Herein, a dual-oxide shell of ZnO/Al₂O₃ as a robust barrier to FeSiAl core is introduced to mitigate corrosion resistance. The FeSiAl@ZnO@Al₂O₃ layer by layer hybrid structure is realized with atomic-scale precision through the atomic layer deposition technique. Owing to the unique hybrid structure, the FeSiAl@ZnO@Al₂O₃ exhibits record-high microwave absorbing performance in low-frequency bands covering L and S bands with a minimum reflection loss (RL_min) of -50.6 dB at 3.4 GHz. Compared with pure FeSiAl (RL_min of -13.5 dB, a bandwidth of 0.5 GHz), the RL_min value and effective bandwidth of this designed novel absorber increased up to ~ 3.7 and ~ 3 times, respectively. Furthermore, the inert ceramic dual-shells have improved 9.0 times the anti-corrosion property of FeSiAl core by multistage barriers towards corrosive medium and obstruction of the electric circuit. This is attributed to the large charge transfer resistance, increased impedance modulus |Z|_0.01 Hz, and frequency time constant of FeSiAl@ZnO@Al₂O₃. The research demonstrates a promising platform toward the design of next-generation MAs with improved anti-corrosion properties.

Corrosion Behavior and Mechanical Properties of a Nanocomposite Superhydrophobic Coating

In this work, a mechanically durable anticorrosion superhydrophobic coating is developed using a nanocomposite coating solution composed of silica nanoparticles and epoxy resin. The nanocomposite coating developed was tested for its superhydrophobic behavior using goniometry; surface morphology using scanning electron microscopy and atomic force microscopy; elemental composition using energy dispersive X-ray spectroscopy; corrosion resistance using atomic force microscopy; and potentiodynamic polarization measurements. The nanocomposite coating possesses hierarchical micro/nanostructures, according to the scanning electron microscopy images, and the presence of such structures was further confirmed by the atomic force microscopy images. The developed nanocomposite coating was found to be highly superhydrophobic as well as corrosion resistant, according to the results from static contact angle measurement and potentiodynamic polarization measurement, respectively. The abrasion resistance and mechanical durability of the nanocomposite coating were studied by abrasion tests, and the mechanical properties such as reduced modulus and Berkovich hardness were evaluated with the aid of nanoindentation tests.

Self-Healing Performance of Smart Polymeric Coatings Modified with Tung Oil and Linalyl Acetate

This work focuses on the synthesis and characterization of polymeric smart self-healing coatings. A comparison of structural, thermal, and self-healing properties of two different polymeric coatings comprising distinct self-healing agents (tung oil and linalyl acetate) is studied to elucidate the role of self-healing agents in corrosion protection. Towards this direction, urea-formaldehyde microcapsules (UFMCs) loaded with tung oil (TMMCs) and linalyl acetate (LMMCs) were synthesized using the in-situ polymerization method. The synthesis of both LMMCs and TMMCs under identical experimental conditions (900 rpm, 55 °C) has resulted in a similar average particle size range (63-125 µm). The polymeric smart self-healing coatings were developed by reinforcing a polymeric matrix separately with a fixed amount of LMMCs (3 wt.% and 5 wt.%), and TMMCs (3 wt.% and 5 wt.%) referred to as LMCOATs and TMCOATs, respectively. The development of smart coatings (LMCOATs and TMCOATs) contributes to achieving decent thermal stability up to 450 °C. Electrochemical impedance spectroscopy (EIS) analysis indicates that the corrosion resistance of smart coatings increases with increasing concentration of the microcapsules (TMMCs, LMMCs) in the epoxy matrix reaching ~1 GΩ. As a comparison, LMCOATs containing 5 wt.% LMMCs demonstrate the best stability in the barrier properties than other developed coatings and can be considered for many potential applications.

Smart Coatings Prepared via MAPLE Deposition of Polymer Nanocapsules for Light-Induced Release

Herein, smart coatings based on photo-responsive polymer nanocapsules (NC) and deposited by laser evaporation are presented. These systems combine remotely controllable release and high encapsulation efficiency of nanoparticles with the easy handling and safety of macroscopic substrates. In particular, azobenzene-based NC loaded with active molecules (thyme oil and coumarin 6) were deposited through Matrix-Assisted Pulsed Laser Evaporation (MAPLE) on flat inorganic (KBr) and organic (polyethylene, PE) and 3D (acrylate-based micro-needle array) substrates. SEM analyses highlighted the versatility and performance of MAPLE in the fabrication of the designed smart coatings. DLS analyses, performed on both MAPLE- and drop casting-deposited NC, demonstrated the remarkable adhesion achieved with MAPLE. Finally, thyme oil and coumarin 6 release experiments further demonstrated that MAPLE is a promising technique for the realization of photo-responsive coatings on various substrates.

Recently Emerging Nanotechnological Advancements in Polymer Nanocomposite Coatings for Anti-corrosion, Anti-fouling and Self-healing

Recent nanotechnological advancements have enabled novel innovations in protective polymer nanocomposites (PNC) coatings for anti-corrosion, anti-fouling and self-healing services on material surfaces. Nanotechnology encompases research, manufacturing, and application of nanoparticulate architectures, tubular structures, sheets or plates exhibiting sizes below 100 nanometers (nm) in at least a single dimension. Inclusions of nanoparticles into organic entities have demonstrated enhanced properties essential for attainiment of aesthetics, anti-corrosion, thermal stability for high-temperature performances, mechanical strength essential for resisting coating deterioration in harsh environments, nano-architectural cross-linking capable of hindering penetration of corrosive, and biofouling entities. Unlike previously published literature, this paper elucidates very recently emerging important advancements in novel techniques utilized in developing PNC coatings for applications in aerospace, packaging, automotive, biomedicine, maritime, and oil and gas industries for attaining superior anti-fouling, anti-corrosion, and self-healing behaviors on critical material surfaces. Emerging market structures and novel applications are also presented.

Exploring the corrosion inhibition capability of FAP-based ionic liquids on stainless steel

Corrosion is clearly one of the more common causes of materials failure in stainless steel. To manage corrosion, chemical inhibitors are often used for prevention and control. Ionic liquids due to their hydrophobic and corrosion-resistant property are being explored as alternative protective coatings and anti-corrosion materials. In this particular study, ionic liquids containing functionalized imidazolium cations and tris(pentafluoroethyl)trifluorophosphate (FAP) anions were investigated for their ability to inhibit corrosion on stainless steel surfaces in acidic environment. Using surface characterization techniques, specifically scanning electron microscopy and energy-dispersive X-ray (EDX), the morphology and the elemental composition of the steel surfaces before and after corrosion were determined. Contact angle measurements were also performed to determine how these ionic liquids were able to wet the stainless steel surface. In addition, potentiodynamic studies were carried out to ensure that corrosion inhibition has occurred. Results show that these ionic liquids were able to inhibit corrosion on the stainless steel surfaces. This indicates promise in the use of these FAP-based ionic liquids for corrosion management in stainless steel.

Aramid-Zirconia Nanocomposite Coating With Excellent Corrosion Protection of Stainless Steel in Saline Media

Resistance to stainless steel corrosion in marine-based industries requires more research into materials with an improved surface and enhanced protection by utilizing surface coatings. Herein, a thermally stable aramid–zirconia nanocomposite has been successfully prepared using the sol–gel method to produce a zirconia network-structure bonded to the polymer chain. Using thermal gravimetric analysis (TGA), the residue mass of zirconia retained after the thermal degradation of aramid-zirconia film was determined and found to be 10% by mass. The investigated nanocomposite (using 10% zirconia) was coated on the stainless-steel surface through a facile and effective spin coating method and its protection was examined in saline solution (3.5% NaCl). The aramid–zirconia nanocomposite coating (Ar-Zr10) was found to provide an outstanding corrosion resistance to steel surfaces which led to protecting it against the corrosive marine environment. The electrochemical impedance (EIS) measurements were carried out to evaluate steel resistance against dissolution in chloride solution in the absence and presence of the investigated coatings showed a corrosion protection efficiency of 99.3% using Ar-Zr10 compared to 92.1% using pure aramid. Moreover, the potentiodynamic polarization (PDP) plots showed a pronounced decrease in the corrosion current values which confirmed the formation of a passive layer which mitigated the corrosion reaction and ions diffusion. The water contact angle of stainless-steel coated with pure aramid and the aramid–zirconia was found to be 84.2° and 125°, respectively, confirming the hydrophobic nature of the hybrid coating Ar-Zr10. On the other hand, the results achieved through the electrochemical and surface techniques were used to clarify the protection mechanism. The aramid–zirconia nanocomposite coating showed a remarkable protection performance by controlling the charge transfer at the interface between the steel alloy and the electrolyte which prevented the alloy dissolution.

Design of Corrosion Protective and Antistatic Hybrid Sol-Gel Coatings on 6XXX AlMgSi Alloys for Aerospace Application

An inorganic–organic coating based on glycidyl-functionalized silica and zirconia was synthesized by sol-gel technology to protect three types of AlMgSi (6XXX series) alloys against corrosion in aerospace applications. Different parameters such as the solid content, the organic/inorganic ratio of the sols and the deposition conditions were studied with the aim to achieve a tradeoff between the corrosion protection, antistatic performance and low vacuum-induced outgassing. Those parameters directly influence the thickness and the density of the coatings, and therefore the barrier effect against corrosion and the contact electrical resistance, which are affected in opposite ways. To obtain a low contact electrical resistance, silver nanowires (NW) with a high aspect ratio were loaded in the sol-gel matrix with the aim to create a conductive path through the hybrid coating with a low concentration of NWs. The coatings were adapted for AA6063, AA6061 and AA6082, and they all showed an outstanding anti-corrosion performance in different artificial weathering tests, whereas electrochemical impedance spectroscopy permitted the identification of the most critical parameters affecting water uptake. An antistatic performance was demonstrated by the low contact electrical resistance of the coated AA6061 and AA6063 alloys, although the incorporation of NWs showed a detrimental effect on the corrosion protection compared with the unloaded coating.

Graphene Oxide Decorated with Titanium Nanoparticles to Reinforce the Anti-Corrosion Performance of Epoxy Coating

Graphene oxide–titanium (GO-Ti) composite materials were fabricated using GO as a precursor and then anchoring nano titanium (Nano-Ti) particles on GO sheets with the help of a silane coupling agent. Then, the coating samples were prepared by dispersing GO, Nano-Ti particles, and GO-Ti in an epoxy resin at a low weight fraction of 1 wt %. The GO-Ti composites were investigated by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The dispersibility and anti-corrosion mechanism of the coatings were studied by sedimentation experiments, electrochemical impedance spectroscopy (EIS), SEM, and salt spray tests. The mechanical properties of the coatings were analyzed by friction and wear tests. The results showed that the Nano-Ti particles were successfully loaded on the GO surface by chemical bonds, which made GO-Ti composites exhibit better dispersibility in the epoxy than GO. Compared with Nano-Ti particles and GO, the GO-Ti composite exhibited significant advantages in improving the corrosion resistance of epoxy coatings at the same contents, which was attributed to the excellent dispersibility, inherent corrosion resistance, and sheet structure. Among the different proportions of composite materials, the GO-Ti (2:1) material exhibited the best dispersibility and corrosion resistance. In addition, the composite material also greatly improved the wear resistance of the coating.

High Corrosion Protection Performance of a Novel Nonfluorinated Biomimetic Superhydrophobic Zn-Fe Coating with Echinopsis multiplex-like Structure

A simple, low-cost, fluorine-free, and ecofriendly method was applied to prepare a novel superhydrophobic Zn-Fe alloy coating on the surface of carbon steel. First of all, the Zn-Fe coating was obtained in an alkaline glycerol non-cyanide Zn-Fe plating solution. Then tetradecanoic acid was grafted onto the Zn-Fe coating by a coordination reaction, leading to a superhydrophobic surface. The water contact angle was up to 166° and the sliding angle was 4°. The as-prepared superhydrophobic coating exhibited high performances, such as strong adhesion to the substrate, impact resistance, self-cleaning, antifouling, and anticorrosion. Importantly, until now, few reports focus on the use of a non-cyanide alkaline glycerol plating bath for electrodeposition, which is green, composition-stable, and corrosion-free for devices. In addition, the growth mechanism of the Echinopsis multiplex-like hierarchical micro/nanostructure of the superhydrophobic surface was studied in detail.