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• Ammonium bifluoride could dope in the polyethylene glycol (PEG) structure by a chemical reaction. • Ammonium bifluoride doped with PEG in Ppy coating could improve the corrosion properties of AZ31 Mg alloy. • Ppy coating modified by PEG doped ammonium bifluoride could act as a smart inhibited system. • Fluoride released from this system in the response to corrosion damage. In this study, polypyrrole (Ppy) coatings embedded by polyethylene glycol (PEG) doped ammonium bifluoride (doped Ppy) was deposited on the AZ31 Mg alloy using cyclic voltammetry. Fluoride-nuclear magnetic resonance (F-NMR), thermal gravimetric analysis (TGA), and differential scanning calorimetry (DSC) results showed that the doping of fluoride in the polyethylene glycol molecule was implemented. Corrosion performance of the doped Ppy coatings was assessed by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques in 0.05 M NaCl solution. Field emission scanning electron microscopy (FESEM) and energy-dispersive x-ray spectroscopy (EDS) showed that doped Ppy coatings possessed higher corrosion resistance than that of Ppy coating. Charge transfer resistance of doped Ppy coating measured about 2 and 5 times higher than un-doped Ppy and Ppy coatings, respectively which were associated to the synergistic behavior of fluoride with polyethylene glycol as well as its release to the anodic zones. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Mesoporous silica acted as the host of sulfamethazine as inhibitor. • Corrosion inhibitor released from nanocontainer in response to corrosion damage. • Corrosion resistance of coatings with MSInh was improved due to inhibitor release. • Sulfamethazine could link to d-orbital of iron and raise the corrosion resistance. Abstract In this study, mesoporous silica served as the host for an eco-friendly corrosion inhibitor. This material could adsorb and release corrosion inhibitor in different aqueous media. A composite coating was prepared by embedding 1 wt. % mesoporous silica loaded with sulfamethazine (MSInh) as the corrosion inhibitor into the epoxy film to protect mild steel as substrate. Anti-corrosion properties of the solution containing MSInh and corrosion protection function of composite coating were assessed by electrochemical impedance spectroscopy. Results showed the higher corrosion protection of epoxy/mesoporous silica loaded with inhibitor (MSInh) in NaCl solution for one month of immersion in comparison with epoxy/mesoporous silica and epoxy coatings. Charge transfer resistance of epoxy, epoxy/MS, and epoxy/MSInh after 30 days of immersion estimated 6, 15, and 80 kΩ cm2, respectively. The results revealed the higher corrosion resistance of epoxy/MSInh which confirmed the barrier effect of mesoporous silica against corrosive species and corrosion inhibiting effect of the released sulfamethazine molecules. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Mesoporous silica (MS) acted as the host of molybdate ion (corrosion inhibitor). • Corrosion inhibitor released from nanocontainer in response to corrosion damage. • Corrosion resistance of coatings with MSInh was improved due to inhibitor release. Abstract In this study, mesoporous silica nanocontainers (MS) were successfully synthesized, functionalized and loaded with sodium molybdate as a corrosion inhibitor (MSInh). The epoxy composite coatings were applied on the mild steel substrates by embedding 1 wt. % mesoporous silica with (E/MSInh) or without (E/MS) inhibitor. Characterization of the synthesized mesoporous silica loaded with molybdate demonstrated the pH-dependence of molybdate release from E/MSInh. According to the results, by increasing the pH from 1 to 14, a 160 times increase in the molybdate concentration in the solution was observed. The corrosion behavior of the composite coatings was assessed by the electrochemical impedance spectroscopy and the electrochemical noise analysis. Charge transfer resistance decreased from 4 × 107 to 3.1 × 104 Ω cm2 and from 2.2 × 106 to 2 × 103 Ω cm2 for E/MSInh and E/MS during the immersion time, respectively. The results revealed the higher corrosion resistance of E/MSInh during 56 days of immersion in 3.5 wt. % NaCl solutions in comparison to E/MS which confirms the proper corrosion inhibiting effect of the released molybdate ions. [ABSTRACT FROM AUTHOR]

In the present study, the formation of superhydrophobic (SHP) structure on the surface of Mg alloy was investigated by immersion in the CuCl2 and NiSO4 solutions following by soaking in the stearic acid (SA) solution. The results revealed the presence of some stearic acid bonds on the surface of Mg alloy. The contact angle of the surface after the process measured about 151.5°, which could be due to the presence of flake-like morphology and the adsorption of hydrophobic substances of SA. X-ray diffraction pattern showed the presence of NiO as the resistant phase against the diffusion of species. Besides, the values of noise and corrosion resistance regarding SHP Mg were at least three orders of magnitude higher than that of bare Mg alloy due to the formation of SHP structure. [ABSTRACT FROM AUTHOR]

In this study, a fine-grained structure was obtained in high-Mn austenitic steel through martensite treatment. The corrosion response of fine-grained and coarse-grained steels was studied and compared in 3.5 wt.% NaCl solution. Electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, and Mott-Schottky analysis were performed to understand the effect of grain refinement on the electrochemical behavior of this steel. Microstructural evaluation showed that by reduction in grain size, the amount of low energy grain boundaries was increased, which led to better electrochemical behavior. In addition, the corrosion resistance of fine-grained steel did not deteriorate in comparison with coarse-grained steel. Both specimens showed a charge-transfer resistance of about 4-5 kΩ cm in NaCl. Besides, a protective film related to fine-grained sample was detected by EIS and Mott-Schottky analysis, which could be a sign of higher grain boundaries in this steel. [ABSTRACT FROM AUTHOR]

In this study, mesoporous silica served as a host for corrosion inhibitor. This material could adsorb and release corrosion inhibitor in different aqueous media. However, the extent of corrosion inhibitor release in the alkaline media was higher. By dispersing 1 wt% mesoporous silica loaded with sodium molybdate in the epoxy layer, a protective composite coating was produced. The corrosion properties of the composite coatings were assessed by electrochemical impedance spectroscopy. Results showed higher corrosion resistance of epoxy/mesoporous silica loaded with inhibitor in the NaCl media for eight weeks of immersion in comparison with epoxy/mesoporous silica. Corrosion inhibitors released from nano-containers in the response to corrosion damage at the interface zone. [ABSTRACT FROM AUTHOR]

In this study, Zn-Co-Mo coatings were deposited on the steel substrate from a citrate bath after adjusting pH, concentration, and current density. The morphology, the content of alloying elements, and the thickness of deposits were studied. Deposition behavior of these ternary coatings was examined by cathodic polarization and cyclic voltammetry (CV) techniques. The synthesized deposits were investigated by scanning electron microscopy (SEM), energy-dispersive x-ray (EDX) analysis, x-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization methods. The results showed that the deposition potential of Zn-Co-Mo alloy was feasible in negative potentials higher than about −1.25 V versus Ag/AgCl. Moreover, the corrosion behavior of these coatings was found to be related to the extent of Mo as well as the local anodes and cathodes. The amount of molybdenum in the Zn-Co-Mo coating varied from 2.6 to 14 wt.% as a result of changing the pH. Based on the experimental findings, a narrow range of pH values between 5 and 5.5 could contribute to the high quality of coating in conjunction with the corrosion resistant alloy. Besides, the coatings with Mo element could show a passive-like behavior in the anodic region. [ABSTRACT FROM AUTHOR]

AZ31 Mg alloy surface was coated with polyethyleneimine (PEI) coating with anticorrosive properties in a two-step process to improve corrosion resistance. In the first step, alkaline passivation was followed by a PEI cationic polymer dip coating based on chemical and electrostatic interactions. AZ31 Mg alloy coated with PEI showed better corrosion resistance in PBS than uncoated alloy, based on electrochemical tests including potentiodynamic polarization and electrochemical impedance spectroscopy. Biocompatibility and in vitro cell behavior tests revealed good adhesion and proliferation in the presence of amine groups in the PEI structure. Furthermore, the antibacterial research showed that PEI-coated AZ31 had a great antibacterial activity. These findings suggest that PEI-coated AZ31 Mg implants are suitable for orthopedic applications as bioactive and protective biomaterials. [ABSTRACT FROM AUTHOR]

Abstract: Copper thin films were deposited on oxidized silicon at a substrate temperature of 70°C and 150°C using EB-PVD technique. The morphology and crystal orientation of the deposited film were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. Corrosion behavior of films was studied through electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, immersion test, and cathodic chronopotentiography. Additionally, the crystalline structure of corroded samples immediately after polarization was examined by XRD. Corrosion current density for copper deposits was higher than copper sheet by polarization tests, while the data obtained by the EIS technique emphasized higher corrosion current density for copper sheet. However there was a conflict between polarization and EIS data, the other results obtained by immersion and cathodic chronopotentiography tests proved that the corrosion resistance of copper deposits was higher than copper sheet in the same alkaline media, which can be attributed to chemical composition and higher thickness of the passive layer formed on copper deposits. On the other hand, breakdown potential (Ebp) for copper sheet was about 0.3VSCE, while a distinct Ebp was not found for copper deposits. This was a sign of higher stability of the passive layer formed on copper deposits. The XRD patterns of samples immediately after polarization showed a higher content of Cu(OH)2 on copper deposits in comparison with copper sheet. The stable morphology formed on the surface of copper after polarization was monoclinic CuO, which is assumed to have a significant effect on copper protection in alkaline media. This morphology was more compact on copper deposits in comparison with copper sheet. This was due to higher ability of deposits to react with hydroxyl ions. [ABSTRACT FROM AUTHOR]

Abstract: Copper thin films were deposited on oxidized single crystal silicon and glass surfaces, at 70°C and 150°C substrate temperature using Electron Beam-Physical Vapor Deposition technique. The morphology and crystal orientation of the deposited film were investigated by SEM and XRD, respectively. Corrosion behavior of these films in hydrochloric acid was studied by potentiodynamic polarization method. Results showed that the corrosion resistance of CG 70 (deposit on glass at 70°C substrate temperature) was higher than all deposits and than copper sheet because of its higher ability to form passive layer. [Copyright &y& Elsevier]

The present study aims to investigate the loaded mesoporous silica with sulfamethazine and the effect of its dispersion in the epoxy coating on the corrosion behavior of coated mild steel. The composite coating was synthesized by mixing 1wt. % mesoporous silica without (Mes) and with sulfamethazine (Mes-S) and an epoxy polymer. Electrochemical impedance spectroscopy (EIS), field emission scanning electron microscopy (FESEM), and X-ray photoelectron spectroscopy (XPS) were used to analyze corrosion resistance of the epoxy coating containing Mes and Mes-S. Results revealed the higher corrosion resistance of epoxy/Mes-S in the NaCl solution after 1000 h of immersion compared to epoxy/Mes, indicating higher barrier behavior of epoxy/Mes-S due to the inhibition effect of sulfamethazine. Specifically, epoxy/Mes-S exhibited a Rct of 67 kΩ cm2 after 1000 h of immersion, while the epoxy/Mes and epoxy showed Rct of 9.8 and 7 kΩ cm2, respectively. Besides, it was shown that the epoxy/Mes-S coating could inhibit the growth of E. coli as the antibacterial coating due to the effect of sulfamethazine on the bacteria. [ABSTRACT FROM AUTHOR]

• 316L SS was fabricated by laser powder bed fusion (L-PBF) process. • L-PBF processed steel showed fine cellular/columnar structure due to rapid cooling. • The formation of passive layer on the L-PBF processed steel is favored in the alkaline media. • Better corrosion performance was observed for L-PBF processed steel. This study investigates the microstructure and electrochemical behavior of 316 L processed through laser powder bed fusion (L-PBF) and the related commercial wrought counterpart in the concrete pore solution (0.9 M NaOH + 0.9 wt% NaCl). Analyses showed that the L-PBF method did not decline the corrosion resistance of 316L SS in the alkaline solution. Even in some cases, L-PBF processed alloy showed better electrochemical behavior compared the wrought alloy. Microscopy evaluation indicated that L-PBF processed specimen showed an ultrafine cellular/columnar structure with the more uniform morphology at the higher magnifications compared to the wrought sample, possibly because of the excessive cooling rate of the L-PBF process. Besides, electrochemical studies revealed that corrosion current density related to the L-PBF processed sample reported about one-third of wrought counterpart. Also, L-PBF processed alloy identified the lower defect density compared to the wrought one. The better corrosion performance of the L-PBF processed 316L SS could be related to the fabrication method of the additively manufactured samples, which hindered the presence of detrimental phases and more stability of the passive film. [ABSTRACT FROM AUTHOR]

The concept of intelligence has many applications, such as in coatings and cyber security. Smart coatings have the ability to sense and/or respond to external stimuli and generally interact with their environment. Self-healing coatings represent a significant advance in improving material durability and performance using microcapsules and nanocontainers loaded with self-healing agents, catalysts, corrosion inhibitors, and water-repellents. These smart coatings can repair damage on their own and restore mechanical properties without external intervention and are inspired by biological systems. Properties that are affected by either momentary or continuous external stimuli in smart coatings include corrosion, fouling, fungal, self-healing, piezoelectric, and microbiological properties. These coating properties can be obtained via combinations of either organic or inorganic polymer phases, additives, and pigments. In this article, a review of the advancements in micro/nanocapsules for self-healing coatings is reported from the aspect of extrinsic self-healing ability. The concept of extrinsic self-healing coatings is based on the use of capsules or multichannel vascular systems loaded with healing agents/inhibitors. The result is that self-healing coatings exhibit improved properties compared to traditional coatings. Self-healing anticorrosive coating not only enhances passive barrier function but also realizes active defense. As a result, there is a significant improvement in the service life and overall performance of the coating. Future research should be devoted to refining self-healing mechanisms and developing cost-effective solutions for a wide range of industrial applications. [ABSTRACT FROM AUTHOR]

Commercially available 316L (1.4404) stainless steel is commonly used for industrial filtration due to its combination of good material properties, particularly its corrosion resistance, which is a critical factor for filters in corrosive (e.g., saltwater) environments. Recently, laser powder bed fusion (LPBF) has enabled new more complex and efficient filtration pieces to be manufactured from this material. However, it is critical to know how the corrosion resistance is affected by this manufacturing strategy. Here, the corrosion resistance of LPBF manufactured 316L stainless steel is compared with wrought 316L sheet. The corrosion of the samples in saltwater was assessed with asymmetric electrochemical noise, potentiodynamic polarisation curve, and electrochemical impedance spectroscopy. The samples before and after corrosion were examined with scanning electron microscopy and energy-dispersive spectroscopy. The LPBF samples had higher corrosion resistance than the sheet samples and were more noble. The corrosion resistance of the LPBF sample increased with time, while the wrought sample corrosion resistance reduced over time. The corrosion mechanism of both samples was stable with time, formed of a passive film process and a bared material process. This paper presents the first study about the temporal evolution of the LPBF 316L stainless steel corrosion mechanism. [ABSTRACT FROM AUTHOR]

Marine structures are constantly exposed to the corrosive effects of seawater, making effective corrosion protection crucial for their longevity and performance. Sacrificial anodes, commonly made of zinc, aluminum, or magnesium alloys, are widely employed to mitigate corrosion by sacrificing themselves to protect the steel structures. However, the selection and implementation of sacrificial anode materials present various challenges that need to be addressed. This paper explores the challenges associated with sacrificial anode materials for steel structures and provides potential solutions. To overcome these challenges, the paper proposes solutions such as using advanced alloy compositions, protective coatings, hybrid anode systems, and improved design considerations. Furthermore, the importance of monitoring techniques to assess the performance and remaining lifespan of sacrificial anodes is emphasized. Several case studies and experimental findings are discussed to illustrate the effectiveness and limitations of sacrificial anode materials based on zinc alloys, aluminum alloys, and magnesium alloys. The paper highlights the need for ongoing research and development efforts to address the evolving demands of corrosion protection in marine environments. [ABSTRACT FROM AUTHOR]

Corrosion protection of mild steel (MS) substrate is critical to prolonging the life of service equipment in refineries and chemical industries. In petroleum refineries, drilling and acidizing pipe work with vast amounts of 15% HCl that induce corrosion of MS pipelines. Here, a novel pentadecyl phenol (originated from cashew nut shell liquid)-functionalized conjugated polypyrrole (MPY) was synthesized and demonstrated for MS corrosion inhibition at a 15% HCl environment. Pentadecyl units provide hydrophobicity and form interdigitating layer structures to cover the metal substrate, which leads to better corrosion mitigation. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) studies reveal the superior corrosion inhibition performance of MPY on MS under 15% HCl conditions. The corrosion protection efficiency was determined to be 67.93% over MS substrate in the presence of MPY from PDP studies compared with pure MS. [ABSTRACT FROM AUTHOR]

The chemical, electrochemical and microbiological corrosive degradation of metals is a versatile harmful problem that causes significant economic loss all over the world. The mitigation of these undesired processes needs basic knowledge on the mechanisms of processes in order to control these reactions with environmentally acceptable chemicals and techniques. This paper focuses on the up-to-date possibilities that help in the mitigation of chemical/electrochemical corrosion and, at the same time, in decrease the deposition of corrosion relevant microorganisms, as the microbes in biofilms are more dangerous than the planktonic cells. Some chemicals or coatings due to their specific properties can fulfill multiple functions; they are able to control the corrosion caused by aggressive materials (that could be the metabolites of a corrosion relevant microorganism) and, at the same time, reduce the microbial adhesion. These additives that have important application possibilities in the chemical industry, marine environment, medical field, nanoelectronics, etc., can save energy, materials consumption and cost, and, at the same time, the efficiency is improved. All resolutions will be brought into prominence when the same chemicals (either in dissolved form or in coatings/nanolayers) can effectively control the different appearance of corrosion and, additionally, the microbial adhesion and microbiologically influenced corrosion. [ABSTRACT FROM AUTHOR]

The influence of three polyindole samples on the corrosion rate of mild steel in the absence and presence of different amounts of acetonitrile was investigated in 1-M HClO4. All samples were characterized by Scanning Electron Microscopy, Energy-Dispersive X-ray Spectroscopy, Fourier transform infrared spectroscopy, UV–vis spectroscopy, X-ray Powder Diffraction, and contact angle measurements. Through measurements, it was determined that the polymers differ from each other on the basis of morphology, conjugation, molecular mass, and crystallinity. Also, it was found that all samples include FeCl3 used as an oxidant. The corrosion tests were performed using Electrochemical impedance spectroscopy and polarization curve technique. Among the samples, PIn1 has the highest anti-corrosive property as it includes the highest amount of Fe and the highest density of hydrophobic group, such as ClO4−. According to the characterization measurement recorded after corrosion tests, corrosion species (based on Fe compound) are formed and they increased the passive film protection. From the electrochemical measurement results, it was found that PIn1 inhibited the cathodic corrosion reaction of MS in 3.5% NaCl and showed 98% protection efficiency. Long-term stability analysis shows that Rct increases with time indicating passive film protects the mild steel. So it was found that all polyindole-based inhibitors have a synergistic inhibition effect in the solution. Also, the temperature effect was investigated in the corrosion protection ability of polyindol-based inhibitor. [ABSTRACT FROM AUTHOR]

In the present work, the causes of failure have been investigated for a steel pipe that was abandoned after some time of service in a separation unit of gas facilities. These pipes are exposed to the natural gas and industrial atmosphere. Therefore, the damage to the steel pipes of the separation unit was investigated through several comprehensive analytical investigations, including an optical microscope (OM), quantometer, XRD, FE-SEM, EDS, and microhardness. Moreover, the corrosion resistance was studied through polarization and EIS analysis to elucidate the most plausible reactions and corrosion mechanisms. Visual observations indicated a significant reduction in the thickness of the pipes, and the metallographic studies showed exacerbated voids and porosities in the inner surface. Further studies proved severe uniform corrosion associated with pitting in the pipe's inner side and the removal of corrosion products by the gas flow, which confirmed the EIS results. According to the EDS and XRD results, the composition of the corrosion products was found to be Fe2O3, Fe3O4, and FeCO3. However, the porous and loose corrosion products presented an unprotective layer over the material. Based on the features of the material and the oil site conditions, some recommendations were proposed to reduce the corrosion rate, and prolong the service life of the pipes in the separation unit. [ABSTRACT FROM AUTHOR]

The need for a more sustainable and accessible source of energy is increasing as human society advances. The use of different metallic materials and their challenges in current and future energy sectors are the primary focus of the first part of this review. Cryogenic treatment (CT), one of the possible solutions for an environmentally friendly, sustainable, and cost-effective technology for tailoring the properties of these materials, is the focus of second part of the review. CT was found to have great potential for the improvement of the properties of metallic materials and the extension of their service life. The focus of the review is on selected surface properties and corrosion resistance, which are under-researched and have great potential for future research and application of CT in the energy sector. Most research reports that CT improves corrosion resistance by up to 90%. This is based on the unique oxide formation that can provide corrosion protection and extend the life of metallic materials by up to three times. However, more research should be conducted on the surface resistance and corrosion resistance of metallic materials in future studies to provide standards for the application of CT in the energy sector. [ABSTRACT FROM AUTHOR]

This study presented a novel corrosion protective coating based on polyacrylic/siloxane-silica (PEHA-SS) deposited on lightweight cast aluminium alloy AlSi7Mg0.3. The synthesis of PEHA-SS comprises organic monomer 2-ethylhexyl acrylate and organically modified silane 3-(trimethoxysilyl)propyl methacrylate as well as an inorganic silane, tetraethyl orthosilicate. The steps during the synthesis process were monitored using real-time infrared spectroscopy. The coating deposited onto the AlSi7Mg0.3 surface was characterised using various techniques, including infrared spectroscopy, 3D contact profilometry, and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. The corrosion resistance of the coated alloy in sodium chloride solutions was evaluated using electrochemical impedance spectroscopy. The accelerated testing of the uncoated and coated sample was performed using the Machu test. This novel, nine micrometres thick PEHA-SS coating achieved durable corrosion (barrier) protection for the AlSi7Mg0.3 alloy in 0.1 M NaCl during the first four months of immersion or under accelerated corrosion conditions in a Machu chamber containing NaCl, acetic acid, and hydrogen peroxide at 37 °C. [ABSTRACT FROM AUTHOR]

Science and engineering research studies are currently concentrating on synthesizing, designing, producing, and consuming ecologically benign chemical species to replace harmful chemicals. This is due to the increasing demands of conservation knowledge and strict ecological regulations. Numerous environmentally friendly substitutes produced from natural resources, including biopolymers, plant extracts, chemical pharmaceuticals (drugs), and so on, are now frequently used as inhibitors to replace dangerous corrosion inhibitors. Many compounds have been extensively used. A range of methods, including physisorption, chemisorption, barrier protection, thin-film growth, and electrochemical procedures, will be used to provide corrosion resistance. The various kinds of corrosion inhibitors (CIs), the mechanisms underlying inhibition, and the evaluation procedures have all been covered in-depth. This review provides an overview of the relevant literature in which researchers and scientists used different types of CIs, the effect of CIs on metals, and information about designs and mechanisms used to minimize corrosion in a variety of equipment composed of alloys or metals, along with electrochemical evaluation studies. This review will provide scholars with fresh insights to advance the discipline. [ABSTRACT FROM AUTHOR]

The combination of excellent physical qualities and biocompatibility has made magnesium (Mg) alloys a viable light alloy, particularly for automotive, aerospace, and pharmaceutical applications. However, in most environments, Mg alloys are easily corroded, thus preventing their extensive use. Surface protection by coating is an affordable method for preventing corrosive media from contacting Mg substrate. The development of smart self-healing coatings has attracted attention for surface coating of Mg alloys, as it can impede corrosion reactions, repair mechanical damage, and enable the substrate to function normally again. This article briefly reviews the promising approach of smart self-healing coatings, state-of-the-art coatings, and various healing agent encapsulations. Polymerizable healing agents or corrosion inhibitors are encapsulated in containers and embedded in the coating matrices to facilitate autonomous healing mechanisms. This brief explanation and review are expected to give an insight and more opportunities to explore newly designed smart self-healing coatings. [ABSTRACT FROM AUTHOR]

Intelligent pH-sensitive nanocontainers were successfully constructed employing the Layer by Layer (LbL) approach. FESEM, HRTEM, EDS, elemental mapping, zeta-potential, FTIR, TGA, SIMS, UV–Vis, and Tafel polarization examinations were subsequently performed on the nanocontainers. Following the LbL procedure, imaging evaluation using FESEM and HRTEM revealed a 42 percent increase in the diameter of SiO2 nanoparticles with a halo view. The effective layer implantation was confirmed by EDS, elemental mapping, and zeta potential recording. Electrostatic interactions between Hexamine (HMTA) compounds and distinct layers were discovered using FTIR. Nanocontainers were found to contain 2.86 percent HMTA after a thermal study and a SIMS analysis. An analysis using ultraviolet/visible light showed that the nanocontainers discharged HMTA at various rates into mixtures with different pH. Due to the self-release of HMTA from nanocontainers in extreme acidic and basic mixtures, Tafel polarization suggested surface corrosion resistance. [ABSTRACT FROM AUTHOR]

In this work, six groups of non-toxic compounds were tested as inhibitors for mild steel in 1 M HCl solution: glycine (Gly), glutamic acid (Glu), cysteine (Cys), a mixture of three amino acids glycine, glutamic acid, and cysteine (Gly + Glu + Cys); a mixture of dipeptide composed of glycine and glutamic acid with amino acid cysteine (Gly-Glu + Cys); and a tripeptide composed of glycine, cysteine and glutamic acid which is called glutathione (Glt). The inhibition performances of inhibitor systems for steel corrosion were investigated by electrochemical tests (polarization measurements and electrochemical impedance spectroscopy) and surface analyses (atomic force microscopy-AFM, optical microscope, and photoelectron spectroscopy-XPS). Experimental results showed that all six groups of inhibitors affect the reduction of steel corrosion rate, with Glt having the highest efficiency during 4-h immersion (97.3%). Atomic force microscopy and optical microscope showed that the inhibitors are able to protect the metal surface and reduce the extent of corrosion. The existence of the Glt inhibitory film on the steel surface was confirmed by the XPS method. DFT calculations provided useful insights into adsorption of the corrosion inhibitors. [ABSTRACT FROM AUTHOR]

Corrosion is a significant issue with metallic materials, notably in steel due to its extensive use in a variety of industries. Benzoxazine polymers have been used to produce anti-corrosive compounds that have a remarkable ability to limit corrosion. In the same ink line, we have explored a new approach with a very hydrophobic benzoxazine monomer which is co-polymerized with urethane, and its characterization was studied with IR, UV, and NMR techniques. The corrosion resistance of the same is investigated using Tafel polarization and EIS experiment methodologies. The DFT and MEP studies explain the reactivity towards the anti-corrosive properties of the monomer. [ABSTRACT FROM AUTHOR]

In this study, we have investigated the electrochemical corrosion behavior of boron carbide (B4C) ceramic-reinforced Al-Mg-Si matrix composites in various aqueous environments (NaOH, NaCl, HCl, and H2SO4). The samples were produced by the powder metallurgy (P/M) route and the corrosion investigations were conducted by potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) methods. The morphology of the as-prepared and corroded samples was examined by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) studies. The investigations revealed that the corrosion resistance of Al-Mg-Si composites is highest in NaCl medium due to a less negative corrosion potential, higher charge transfer (Rct) resistance, and lower double-layer capacitance (Cdl) as compared to other media. The SEM morphology suggests that B4C ceramics enhance corrosion resistance by forming a protective barrier layer of OH- and Cl- deposits in the composite and unreinforced alloy, respectively. [ABSTRACT FROM AUTHOR]

The purpose of this work is to study the microstructure and electrochemical performance of 316L stainless steel fabricated by the laser powder bed fusion (LPBF) and commercial rolling (Roll) in 0.5M nitric acid solution. The LPBF-manufactured 316L stainless steel had a higher corrosion resistance in nitric acid solution than the Roll steel. According to the electrochemical studies, the impedance modulus (|Z|10mHz) of the LPBF alloy was twice as great as its roll counterpart after 1 day of immersion in nitric acid solution and about 1 kΩ cm2. Moreover, the potentiodynamic polarization test showed that the LPBF alloy had one-fourth the ipass value as the Roll sample, suggesting that the passive layer on the surface of additive manufactured samples is more stable and enriched with Cr2O3. Additionally, the LPBF microstructure did not contain harmful phases like TiN, which can adversely affect the protection performance of the passive layer. [ABSTRACT FROM AUTHOR]

Plasma electrolytic oxidation (PEO) is a preferable process applied to optimize the corrosion and wear properties of metals and their alloys, particularly magnesium (Mg) alloys used in highly demanded medical and aerospace applications. In this project, AZ series alloys (AZ31, AZ61, AZ91), which are the major commercial magnesium alloys, were coated using the PEO process under varying experimental conditions involving electrolyte with Si based ionic chemical networks together with hydroxyl and fluoride functionalities. Surface analysis was carried out using scanning electron microscopy (SEM). Data were further simulated and analyzed using imageJ software. SEM results showed that, increasing the concentration of Al as in AZ91 and AZ61, dendrites-dominated the microstructure at shorter processing times; a cratered-dendritic matrix was obtained at longer processing time. From the composition analysis, fluoride complex peaks were obtained for the higher Al-content alloy (AZ91), due to the localized intensive discharges made regular by the stable β-phases within the Mg matrix. Corrosion analysis was carried out using potentiodynamic polarization. The compact structure, higher growth rate, and stable chemical phases of MgF2 contributed to the highest hardness values ~1271.2 HV and corrosion potential ~−0.18 V for the AZ91 alloy. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to explore how the inhibitor-loaded nanocontainers can be used in the epoxy coating for protection of steel against corrosion. A self-healing anticorrosive coating can be easily fabricated by embedding the inhibitor-loaded nanocontainers into the epoxy coating matrices. For this purpose, first, cerium (a catholic corrosion inhibitor) is encapsulated into silica nanoparticles (SiO2@Ce). Thereafter, an epoxy nanocomposite coating has been prepared on steel substrate using these SiO2@Ce nanoparticles as nanofillers. Design/methodology/approach: To examine the effect of SiO2@Ce nanocontainers on mechanical properties of epoxy coating, the abrasion resistance, impact resistance and adhesion strength of coating have been evaluated. To reveal the effect of SiO2@Ce nanocontainer on corrosion behavior of epoxy-coated steel, the electrochemical impedance spectroscopy (EIS) has been conducted in NaCl solution. Findings: Transmission electron microscopy and scanning electron microscopy/Energy-dispersive X-ray spectroscopy analyses indicate that Ce3+ cations have been successfully loaded into the surface of silica nanoparticles (at the content of approximately 2 Wt.%). Mechanical tests of epoxy nanocomposite coatings indicate that the nanocomposite coatings with nanoparticles content of 2.5 Wt.% provide the highest values of abrasion resistance, impact resistance and adhesion strength. EIS results show that the presence of SiO2@Ce3+ nanocontainers increases both coating resistance and polarization resistance. Along with the improvement the coating barrier performance, Ce inhibitor plays an important role in improving the anticorrosive performance at the steel–electrolyte interface. Originality/value: The application of self-healing epoxy/SiO2@Ce nanocomposite coatings for the protection of carbon steel is very promising. [ABSTRACT FROM AUTHOR]

Superhydrophobic surfaces have been widely used for their corrosion resistance, self-cleaning and anti-icing characteristics. A new two-component superhydrophobic coating was prepared on aluminum alloy, and some application properties were studied. With appropriate silica, the contact angle of the two-component superhydrophobic coating can be 164.4°, and it has good resistance to the continuous hitting of water droplets and the corrosion of acid. Even when it had been continuous impacted by acid droplets for 300 min, the contact angle of the coating was still lager than 150°. However, the coating was easily corroded by sodium hydroxide. Moreover, it can not only reduce its freezing point by more than 5 °C, but also delay the freezing of droplets on aluminum alloy by about 20 s at the temperature of −20 °C. More than that, the growth of ice or frost on it can only cause extremely minor mechanical damage to it. [ABSTRACT FROM AUTHOR]

The purpose of this study is to examine the microstructure and corrosion performance of martensitic stainless steel 17-4 PH produced by laser powder bed fusion (LPBF) and its corresponding rod specimen in sulfuric acid. Based on a microstructural analysis, the LPBF alloy contained melt pools with an ultrafine cellular structure and uniform distribution of elements, including Nb. The LPBF process significantly improved the corrosion resistance of the 17-4 PH stainless steel alloy in sulfuric acid. The alloy manufactured by LPBF had a charge transfer resistance of at least 7 times that of the Rod counterpart and a corrosion current density that was 4 times lower than Rod. The homogeneous distribution of elements during the solidification process improved the electrochemical performance of LPBF 17-4 PH stainless steel due to the development of gentle galvanic cells compared to Rod one. [ABSTRACT FROM AUTHOR]

The unique additive manufacturing (AM) attributes such as tool-less design, on-site fabrication, short production cycle, and complex structures fabrication can make AM market penetration deeper. The sustained improvements in AM's computational hardware and software, advanced automation, affordable equipment, and process, structural, and metallurgical understanding are likely to contribute to AMs' more comprehensive commercial adaptation. However, several scientific and technological issues like process-induced defects and microstructural heterogeneity limit its growth in replacing conventional products. AM mechanical properties are comparable to those produced conventionally, and the same is true about its corrosion behavior. However, AM process uncertainties can vary part properties, causing significant discrepancies in corrosion results. Controlling corrosion in AM alloys requires a proper understanding of the process and microstructural evolution. Optimizing processing conditions is critical for part's high productivity and minimal defects. Similarly, post-processing conditions are vital to infuse desired mechanical and chemical properties. Regardless of the processing conditions, corrosion is integral to material stability that needs scientific input to understand and develop mechanical and microstructural properties for excellent corrosion-resistant AM materials. This study aims to analyze the scientific work done in the corrosion analysis of AM materials and to suggest future work potentials. [ABSTRACT FROM AUTHOR]

Corrosion and tribology are surface phenomena. Modifying surfaces of materials without resorting to altering their bulk properties is an effective route to alleviate corrosion, friction and wear, encountered in engineering applications. With the advancements in the field of nanotechnology, surface protective coatings with nanomaterials can be readily developed to explore their functionality in mitigating chemical/physical damage of surfaces. Surface protection enhances performance and operating lifetimes of industrial machinery components. This review presents insights on various types of recently developed nanostructured coatings, their synthesis routes, corrosion behaviour and tribological performance. It provides the state-of-the-art information on the development of nanostructured coatings, namely, ceramic coatings, metallic coatings and nanocomposite coatings with metal and polymer matrices. Biomimetic approaches in making nanostructured coatings and challenges encountered in the development of nanostructured coatings are highlighted. [ABSTRACT FROM AUTHOR]

In this study, the addition of organic methionine inhibitor (as an eco-friendly inhibitor) to 0.1 M sulfuric acid media on corrosion resistance of 316L austenitic stainless steel (fabricated by rolling method and three-dimensional (3D) printing method) was investigated. Open-circuit potential electrochemical test and impedance, and structural tests such as optical and electron microscopy and x-ray photoelectron spectroscopy were conducted. The results showed that the corrosion resistance in the presence of inhibitor was higher than the sample without inhibitor and the inhibitory efficiency of methionine was increased up to 64% and the resistance to surface transfer between metal oxide and electrolyte was improved up to 2.77 times. The addition of methionine reduced the surface roughness and accumulation of the surface cavities. The chemical and physical adsorption mechanism of the inhibitor (negatively charged side adsorption of the methionine molecule with positively charged anodic regions of the metal surface) occurred at all points on the surface of the sample with the inhibitor. Also, the amount of oxygen in the cavities was reduced and the distribution of sulfur was uniform. The thickness of the passivator oxide layers was calculated more than the sample without inhibition due to the addition of inhibitor. [ABSTRACT FROM AUTHOR]

This article presents a concise review of different types of inhibitors for corrosion protection on metal surfaces. Corrosion inhibitors can be of different types, which include organic, inorganic and hybrid (organic/inorganic) materials. They are also classified as cathodic, anodic and/or mixed-type inhibitors, which are based on the active inhibitor molecules that retard the corrosion process. Silicate, nitrites, molybdates, phosphates, zinc salt and cerium salt are widely used as inorganic inhibitors. Many organic compounds have been widely utilized as inhibitors. Corrosion protection will be obtained by various mechanisms such as physisorption, chemisorption, barrier protection, thin-film formation and electrochemical processes. The type of inhibitors, inhibition mechanism and the evaluation methods have been explained in detail. [ABSTRACT FROM AUTHOR]

This study aims to evaluate the microstructure and corrosion resistance of selective laser-melted 17-4 precipitation hardening (PH) martensitic stainless steel and the corresponding wrought specimen in Ringer's solution. The results showed that the selective laser melting (SLM) process improved the corrosion behavior of the alloy in the solution. Microscopic studies revealed that the wrought sample has fine lath martensite with elongated δ-ferrite stringers, while selective laser-melted (SLMed) alloy did not show any obvious phase. However, at higher magnifications, the SLMed specimen exhibited a fine cellular/columnar microstructure owing to the high cooling rate in the SLM technique and uniform distribution of elements. In addition, corrosion studies emphasized that the SLMed alloy possessed a higher charge transfer resistance than the wrought sample. Charge transfer resistances of the SLMed and the wrought sample were about 14.1 and 1.5 KΩ cm2, respectively. Moreover, corrosion current density of the SLMed alloy after 100 h of immersion was about ten times lower than the wrought one. The improved electrochemical behavior of SLMed 17-4 PH stainless steel can be attributed to the reduction of nonuniform distribution of alloying elements such as Nb during the solidification process as a consequence of high cooling rate of the SLMed alloy. Moreover, the development of galvanic cells and a low anode/cathode area ratio are other factors related to the decreased corrosion performance of the wrought alloy. [ABSTRACT FROM AUTHOR]

Hot cracking susceptibility and the formation of brittle martensite phase are the main factors that limit the weldability of a dissimilar joint between carbon steel (CS) and austenitic stainless steel (SS). In this study, the self-constraint finger test was used to correlate the welding thermo-mechanical field with the crack susceptibility of a dissimilar weld between the CS ASTM A36 and SS AISI 304L. The finger test allowed to intercalate fingers (portions) of tested materials in the weld samples to produce dissimilar welds. The heat dissipation and the distortion behavior were related to the crack susceptibility, critical weld regions extension, and chemical species diffusion. Four samples were welded (two similar welds and two dissimilar welds) using the filler metals ER70S-6 and EC410NiMo. Welds were analyzed through light optical microscopy (LOM) and scanning electron microscopy (SEM) to characterize phases, detect cracks, microstructural changes, and element diffusion. A finite element (FE) numerical model was applied to simulate the welding thermo-mechanical field. FE estimations of distortion and residual stress helped to predict induced crack propagation (the initial gap between fingers) towards the fusion zone. Additionally, electrochemical tests were carried out to assess the corrosion susceptibility of the dissimilar welds. The observed cracks were produced due to different factors such as residual stress distribution, the formation of brittle and untempered martensitic phase in the fusion zone (FZ), and hot cracking associated with the weld sample distortion behavior. According to the FE estimations, the high thermal expansion of the SS was responsible for the bending curvature change in welds 2 and 4, which produced a gap between fingers and increased the crack extension in the FZ of weld 4. The dilution contributed to the formation of δ-ferrite in the FZ, which limited the growth of cold and hot cracks. The decarburization and sensitization were not observed in dissimilar welds due to the low element diffusion. [ABSTRACT FROM AUTHOR]

A hydrothermal deposition method was utilized to fabricate Ca-P composite coating induced by the layer-by-layer (LbL) assembled polyvinylpyrrolidone/deoxyribonucleic acid (PVP/DNA)20 multilayer on AZ31 alloy. The surface morphology and compositions were characterized by SEM, EDS, FTIR and XRD. Besides, the corrosion resistance and degradation behavior of the coating were tested via electrochemical polarization, impedance spectroscopy and immersion measurements. Results show that the main components of Ca-P coatings are hydroxyapatite, Ca3(PO4)2 and Mg3(PO4)2·nH2O. The LbL-assembled DNA and PVP promote the adsorption of Ca-P deposits on the sample surface, and structures and functional groups of the polyelectrolyte in the outermost layer are the primary influencing factor for the induction of the Ca-P coating. Carboxyl groups have the best biomineralization effect among all related functional groups. The enhanced corrosion resistance and adhesion highlight a promising use of (PVP/DNA)20-induced Ca-P coatings in the field of biomedical magnesium alloys. [ABSTRACT FROM AUTHOR]

In this study, microstructural changes in the thermomechanical processing and its effect on the corrosion behavior of 321 austenitic stainless steel were investigated. EDS analysis and optical microscopy were used to identify precipitates and microstructure, respectively. To evaluate the corrosion properties, potentiodynamic polarization test and electrochemical impedance spectroscopy were performed. First, the as-received sample was subjected to cold rolling with a 90% thickness reduction at liquid nitrogen temperature, and then annealing was performed at temperatures of 750, 850, and 1050 °C for 10 min. The results showed that severe cold rolling slightly improved the corrosion properties and in annealed samples, the corrosion resistance increased with more uniform microstructure, more reversion of martensite phase to austenite, and reduction of grain size. Annealed samples at 850 °C and 1050 °C with polarization resistance values of 8.200 kΩ.cm² and 3.800 kΩ.cm² depicted the highest and lowest corrosion resistance compared to other samples, respectively. [ABSTRACT FROM AUTHOR]

Welding of AISI H13 tool steel which is mainly used in mold making is difficult due to the some alloying elements and it high hardenability. The effect filler metal composition on the microstructural changes, phase evolutions, and hardness during gas tungsten arc welding of AISI H13 hot work tool steel was investigated. Corrosion resistance of each weld was studied. For this purpose, four filler metals i.e. ER 312, ER NiCrMo-3, ER 80S, and 18Ni maraging steel were supplied. Potentiodynamic polarization test and electrochemical impedance spectroscopy (EIS) were used to study the corrosion behavior of weldments. It was found the ER 80S weld showed the highest hardness owing to fully martensitic microstructure. The hardness in ER 312 and ER NiCrMo3 weld metals was noticeably lower than that of the other weld metals in which the microstructures mainly consisted of austenite phase. The results showed that the corrosion rate of ER 312 weld metal was lower than that other weld metals which is due to the high chromium content in this weld metal. The corrosion rate of ER NiCrMo-3 was lower than that of 18Ni maraging weld. The obtained results from EIS tests confirm the findings of potentiodynamic polarization tests. [ABSTRACT FROM AUTHOR]

Corrosion of metals induces enormous loss of material performance and increase of cost, which has been a common and intractable issue that needs to be addressed urgently. Coating technology has been acknowledged to be the most economic and efficient approach to retard the metal corrosion. For several decades, polymers have been recognized as an effective anticorrosion coating material in both industries and scientific communities, as they demonstrate good barrier properties, ease of altering properties and massive production. Nanomaterials show distinctively different physical and chemical properties compared with their bulk counterparts, which have been considered as highly promising functional materials in various applications, impacting virtually all the fields of science and technologies. Recently, the introduction of nanomaterials with various properties into polymer matrix to form a polymer nanocomposite has been devoted to improve anticorrosive ability of polymer coatings. In this review article, we highlight the recent advances and synopsis of these high‐performance polymer nanocomposites as anticorrosive coating materials. We expect that this work could be helpful for the researchers who are interested in the development of functional nanomaterials and advanced corrosion protection technology. [ABSTRACT FROM AUTHOR]

Defects in protective-coating systems on steel surfaces are inevitable in practical engineering applications. A composite coating system, including a primer, middle coat and topcoat, were used to protect carbon steel from corrosion in a marine environment. Two environmental additives, glass fibers and thiourea, were applied in the middle coat to modify the coating system. The long-term corrosion durability and self-healing ability of the scratched coating system were evaluated by multiple methods. Results of the electrochemical technologies indicated that the coating system that contained 0.5 wt.% fibers and 0.5 wt.% thiourea presented good corrosion protection and self-healing for carbon steel when immersed in 3.5% NaCl for 120 d. Evolution of localized corrosion factors with time, as obtained from the current distribution showed that fibers combined with thiourea could inhibit the occurrence of local corrosion in scratched coating systems and retarded the corrosion development significantly. Surface characterization suggested that adequate thiourea could be absorbed uniformly on fibers for a long time to play an important role in protecting the carbon steel. Finally, schematic models were established to demonstrate the action of fibers and thiourea on the exposed surface of the carbon steel and the scratched coating system in the entire deterioration process. [ABSTRACT FROM AUTHOR]

Conducting polymers have been used for many years as coating materials against corrosion. However, the coated materials absorb water over time resulting in reduction of resistivity and anticorrosion properties. In this study, poly(N-methylpyrrole) (P(N-MPy)) and P(N-MPy)/titanium dioxide ((TiO2) nanocomposite films were synthesized in 0.5 M oxalic acid solution on Al 1050 electrode by chronoamperometric method. The modified electrodes were characterized by scanning electron microscopy–energy dispersive X-ray analysis, Fourier transform infrared–attenuated transmission reflectance, electrochemical impedance spectroscopy (EIS), and Tafel extrapolation techniques. The corrosion tests results were obtained in 3.5% sodium chloride (NaCl) solution by Tafel plots. In addition, the equivalent electrical circuit model of P(N-MPy) and P(N-MPy)/TiO2 nanocomposite films were investigated in 3.5% NaCl solution at different time periods. The EIS study of the polymer and nanocomposite were analyzed by Matlab program and for the first time Tina, the equivalent electrical circuits program, was used. [ABSTRACT FROM AUTHOR]

Electrochemical scanning tunneling microscopy (ECSTM) was applied to analyze in situ the passivation of grain boundaries on microcrystalline copper in 0.1 M NaOH aqueous solution. Two types of boundaries, assigned to coherent twin and random grain boundaries, were studied in three different states of the copper surface: metallic after cathodic reduction of the air-formed native oxide film, passive after anodic polarization at 0.7 V vs. SHE to form the duplex Cu(I)/Cu(II) oxide film, and metallic after cathodic reduction of the passive film. The depth measured at several sites along the grain boundaries was extracted from statistical line profile analysis and discussed using an original model allowing differentiating metal consumption by dissolution or by passive film formation at grains and grain boundaries. The results highlight different local passivation properties between randomly oriented grains and grain boundaries and also between the two different types of grain boundaries. Both at coherent twin and random grain boundaries, it is found that more copper irreversibly dissolves during passivation and less copper is consumed to grow the passive film, suggesting a more hydroxylated/hydrated composition less dense in copper than on grains. At random grain boundaries, irreversible dissolution is found to be enhanced and the passive film to be thicker. [ABSTRACT FROM AUTHOR]

This work compares the degradation of Mg and Mg-Ca0.3 alloy when they are exposed for 14 days to Hank's solution at 37 °C. A combination of immersion test, electrochemical techniques (PDP, EIS, EN), and surface characterization methods (SEM-EDS, XRD, and XPS) were carried out. The pH change over time, the lower mass loss (≈20%), and the lower concentration of the released Mg2+ ions (≈3.6 times), as well as the lower level of the surface degradation, allowed to consider the positive effect of Ca, presenting Mg-Ca0.3 alloy with lower electrochemical activity than that of Mg. The positive effect of Ca may be due to the formed layer characteristics on the alloy surface, which impedes the cathodic hydrogen evolution and Mg-ions release. The electroless deposited Ag-nano-particles (Ag-NPs) on Mg-Ca0.3 surface were characterized by SEM-EDS, XRD, UV-Vis, and contact angle. The agar-diffusion test was used to compare the growth of Staphylococcus aureus and Escherichia coli bacteria on Mg-Ca0.3 in the presence of Ag-NPs deposits in different size. Zeta-potential of the bacteria was negative, with respect to pH of the Mueller-Hinton culture broth. The greater antibacterial effect of S. aureus was attributed to its more negative zeta-potential, attracting more released Ag+ ions. [ABSTRACT FROM AUTHOR]