Anti-corrosion Mechanism Research Articles

Significantly enhanced corrosion resistance for Fe-based amorphous coatings via sealing treatment: Based on hybridisation and superhydrophobicity strategy

Based on the synergistic effect of hybridisation-superhydrophobicity, a simple and facile spraying method was used to achieve efficient sealing of Fe-based amorphous metallic coatings. In this paper, we employed rare-earth neodymium salts as inorganic sealant raw materials and loaded low surface energy fluorosilanes into epoxy resins to act as organic sealant raw materials. The surface structure and chemical composition of the sealing coatings were systematically characterised. The sealing mechanism as well as the anti-corrosion mechanism of the coating were investigated intensively. The results indicate that the superior corrosion resistance and self-cleaning ability of the sealed coating stems from the inorganic–organic-complex trinity effect: the corrosion inhibition effect of Nd oxide deposited during the inorganic sealing process, the shielding effect of the resin in the organic sealing, and the cross-linking and superhydrophobicity behaviour (liquid repellency effect) of the FDTES-Nd3+-Fe2+ complexes formed on the surface of the coating. This work provides valuable guidelines and insights for the design of subsequent corrosion-resistant and sealing coating.

A simple strategy to significantly improve the anticorrosion and aging resistance of epoxy coatings by adding polyaniline modified multi-walled carbon nanotubes

Epoxy coatings are widely used for corrosion protection of metals, but under extremely harsh environments, the epoxy polymer chains such as the C-O bonds of epoxy ether and aromatic ether, and the -OH in the epoxy chain structure can also undergo aging and degradation, leading to the failure of the coating in service. How to extend the anti-aging capability of epoxy resins while maintaining their other properties unchanged has become a major challenge in the practical application of epoxy coatings. In this study, the polyaniline (PANI) modified multi-walled carbon nanotubes (MWCNT@PANI) were synthesized by polymerization in-situ and added to epoxy resin as an anti-aging filler. The various measurements have been adopted to characterize the composition and structure of MWCNT@PANI, and the anticorrosive performance of the composite coating for carbon steel were evaluated via salt spray, chemical aging and UV light aging. Results showed that the impedance value of the blank epoxy coating decreases by at least two orders of magnitude after the salt spray tests, and the contact angle decreases by about 30° and gradually changes from hydrophobic to hydrophilic, indicating a significant decline in corrosion resistance. In contrast, the composite coating confirmed the excellent anti-aging performance, while the impedance values increased by approximately 2-5 orders of magnitude compared to that in blank epoxy coatings, and remained around 1010 Ω·cm2. Given the dense encapsulation of MWCNT@PANI, the dispersion stability between the filler and EP can be improved, and the effective corrosion resistance performance was also supported by molecular dynamic simulation. Besides that, the ability of free radical quenching along with the labyrinth effect and hydrophobic interaction have also been investigated to explain the anticorrosion and anti-aging mechanism.

Microstructure and properties of a HIP manufactured B4Cp reinforced highly alloyed Al-Zn-Mg-Cu-Zr aluminum matrix composite

In this study, an aluminum matrix composite with good mechanical property and excellent corrosion resistance, B4C particles (B4Cp) reinforced highly alloyed Al-Zn-Mg-Cu-Zr matrix composite, was successfully fabricated through ball-milling, cold isostatic pressing, vacuum degassing, hot isostatic pressing (HIP), homogenization, hot extrusion, solution treatment, and aging treatment. It was found that the B4C/MgAl2O4/Al was the dominant interface structure, which was coherent and enhanced the bonding between the particles and the matrix considerably, while the B4C/Al2O3/Al was the minor interface structure. The grain boundary was very clean in both T4 and T6 aging states, without aging precipitates and O element segregation. In T4 aging state, the composite exhibited superior properties, with the mass density of 2.84 g·cm-3, the elastic modulus of 119.18 GPa, the yield strength of 576.08 MPa, the ultimate tensile strength of 655.27 MPa, the tensile elongation of 1.48%, and the very low electrochemical corrosion current density of 4.4581×10-8 A·cm-2 in 3.5 wt.% NaCl water solution. The MgAl2O4 and BO3-rich interface phases, the strengthening mechanisms and the anti-corrosion mechanisms of the composite were discussed in detail.

Extract of Silybum marianum (L.) Gaertn Leaves as a Novel Green Corrosion Inhibitor for Carbon Steel in Acidic Solution

In this work, leaves of Silybum marianum (L.) Gaertn were extracted by a one-step extraction method using ethanol as a solvent, and the Silybum marianum (L.) Gaertn extract (SMGE) was firstly employed as a green corrosion inhibitor for carbon steel in 0.5 mol/L H2SO4. The corrosion inhibition performance was studied using weight loss and electrochemical methods, and the anti-corrosion mechanism of SMGE is further analyzed through some surface characterizations and theoretical calculations. The results indicate that SMGE can act as a mixed-type corrosion inhibitor and possess superior corrosion inhibition performance for carbon steel in H2SO4 solution, and the optimum corrosion inhibition efficiency reached 93.06% at 800 ppm SMGE combined with 60 ppm KI. The corrosion inhibition efficiency increased with the rising inhibitor concentration. Surface characterizations illustrated that the inhibitor could physico-chemically adsorb on a metal surface, forming a hydrophobic, protective film.

The anticorrosion behavior and mechanism of Ti3C2 nanosheets for titania pigmented epoxy coatings

Utilization of Ti3C2 nanosheets for enhancing anticorrosion of epoxy resin coatings has been reported. But the epoxy coatings in real world are mainly pigmented coatings. Unfortunately, the anticorrosion behavior of Ti3C2 nanosheets for the pigmented epoxy coatings is rarely concerned. In this work, both 0.5 wt% unmodified Ti3C2 nanosheets (U-Ti3C2) or 0.5 wt% (3-glycidyloxypropyl)trimethoxysilane-modified Ti3C2 nanosheets (G-Ti3C2) were introduced into solvent-based titania pigmented epoxy coatings. Corrosion resistance of coatings was evaluated by electrochemical impedance spectroscopy and salt spray tests. A titania concentration effect was interestingly exhibited for the anticorrosion behavior Ti3C2-containing pigmented coatings. Enhanced anticorrosion was only demonstrated when TiO2 content was not above 10 wt% for U-Ti3C2 or 5 wt% for G-Ti3C2. Moreover, the pigmented coatings with U-Ti3C2 have better corrosion resistance than those with G-Ti3C2, being contrary to the phenomenon observed in pure epoxy resin coatings. The different anticorrosion behavior of Ti3C2 nanosheets for epoxy coatings with various TiO2 contents was mainly attributed to the different dispersion states of TiO2 pigments, that is, improved dispersion at low TiO2 content and deteriorated dispersion at high TiO2 content, after addition of Ti3C2 nanosheets.

Enhancing anticorrosion performance of metals by incorporating cellulose nanofibrils/α-ZrP composite as nanofiller into water-based coating

The anticorrosion of metals has gain considerable interest in view of economic and environmental issues. Coating protection is one of the most effective and cost-effective methods for anticorrosion of metals. However, the traditional coatings often suffer from many issues such as poor performance or high cost. For the first time, a strategy was proposed by constructing cellulose nanofibrils (CNF)/alpha‑zirconium phosphate (α-ZrP) composite as nanofiller and incorporating into water-based coatings for anticorrosion of metals. The successful coordination of α-ZrP nanosheet and CNF were characterized. The effects of the resultant composite on anticorrosion performance were investigated. The results showed that, the as-prepared coating exhibited superior anticorrosion performance to commercial coatings. The impedance of the test sample coated with the as-prepared coating reached up to 4.38 × 105 Ω when it was immersed in 3.5 % NaCl solution with few corrosions fragmentation on metal surface, exhibiting a favorable long-term anticorrosion performance. Meanwhile, the anticorrosion mechanism was proposed. It is expected that this strategy would provide novel solutions for developing highly efficient water-based anticorrosive coatings of metals.

A Review on SEM Imaging of Graphene Layers

Atomic-thick graphene has stimulated great interests for exploring fundamental science and technological applications due to its promising electronic, mechanical and thermal properties. It is important to gain a deeper understanding of geometrical/structural characteristics of graphene and its properties/performance. Scanning electron microscopy (SEM) is indispensable for characterizing graphene layers. This review details SEM imaging of graphene layer, including the SEM image contrast mechanism of graphene layers, imaging parameter-dependent contrast of graphene layers and the influence of polycrystalline substrates on image contrast. Furthermore, a summary of SEM applications in imaging graphene layers is also provided, including layer-number determinations, study of chemical vapor deposition (CVD)-growth mechanism, and reveal of anti-corrosive failure mechanism of graphene layers. This review will provide a systematic and comprehensive understanding on SEM imaging of graphene layers for graphene community.

Comprehensive assessment of the corrosion inhibition properties of quinazoline derivatives on mild steel in 1.0 M HCl solution: An electrochemical, surface analysis, and computational study

The efficacy of two compounds, namely 12-(4-chlorophenyl)-3,3-dimethyl-3,4,5,12-tetrahydrobenzo[4,5] imidazo[2,1-b]quinazolin-1(2H)-one (Q-Cl) and 3,3-dimethyl-12-phenyl-3,4,5,12-tetrahydrobenzo[4,5]imidazo[2,1-b]quinazolin-1(2H)-one (Q-H), in inhibiting corrosion on mild steel in 1.0 M hydrochloric acid was evaluated. Surface analytical techniques and electrochemical procedures were employed for examination. The results demonstrated that both Q-Cl and Q-H significantly inhibit corrosion. Specifically, Q-Cl achieved an inhibition efficiency of 85.2 % at a concentration of 10⁻³ M, while Q-H exhibited a higher inhibition efficiency of 91.5 %. Electrochemical investigations suggested that both Q-Cl and Q-H acted as inhibitors of mixed-type corrosion. These chemicals efficiently prevented metal corrosion through adsorption, conforming to Langmuir's adsorption isotherm model. The adsorption mechanism of corrosion inhibition was further supported by surface investigations and scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDX). Additionally, Density Functional Theory (DFT) and other computational approaches were employed to study the anti-corrosion mechanism of Q-Cl and Q-H. These simulations yielded theoretical results that aligned with the preceding experimental findings.

Atomistic Analysis of Sulphonamides as a Microbial Influenced Corrosion (MIC) Inhibitor.

Four sulfonamide-type microbial inhibitors were studied using density functional theory (DFT) to assess their effectiveness in controlling microbial corrosion. The experimental techniques (FTIR, SEM, EIS, EFM, and AFM) are beneficial for measuring properties such as chemical composition, bond formation, electrochemical behavior, and surface topography; however, DFT can be useful as a new method for understanding microbial corrosion. Sulfacetamide (SFC), sulfamerazine (SFM), sulfapyridine (SFP), and sulfathiazole (SFT) uniformly adsorb onto the iron surface and block the active site, reducing the corrosion rate. To study the effect on microbial activity, a 0.6 eV electric field was applied. The absolute increase in the interaction energy indicates that sulfonamides are effective microbial inhibitors. Electronic SFC, SFM, SFP, and SFT descriptors agree with the experimental inhibition efficiency. The shift of the density of state (DOS) toward a low energy level for sulfonamides indicates the stabilization of these molecules at the Fe (100) surface. The population analysis combined with atomic and molecular parameters further explains the anticorrosive mechanism of sulphonamides.

Insight into the Anti-Corrosion Mechanism of Halogen Anions in Bisimidazoline Derivatives as Corrosion Inhibitor for Q235 Steel in 1.0 mol/L HCl

Insight into the Anti-Corrosion Mechanism of Halogen Anions in Bisimidazoline Derivatives as Corrosion Inhibitor for Q235 Steel in 1.0 mol/L HCl

Multifunctional organic-inorganic hybrid coating for enhanced bronze corrosion protection

Bronze relics with vital historical, artistic, and scientific value, are one of the significant symbolizations of human civilization. However, due to the long burial time and the change in storage conditions, an inevitable and thorny problem arises in preventing the ancient bronze relics from corrosion. Coatings have great potential for metal corrosion protection at present. This study prepared a multifunctional coating consisting of zinc oxide (ZnO), titanium dioxide (TiO2), and fluoroethylene vinyl ether (FEVE) polymer by an organic-inorganic hybrid, which was applied onto the surface of corroded bronze using a self-assembly method and spraying. The rough structure of composite coating resembling that of the mastoid structure found on lotus leaf, effectively prolongs the transmission path of corrosive ions while preventing bronze contact with the corrosive media. Additionally, this study mainly investigated the bronze anti-corrosion mechanism through an electrochemical analysis perspective. Electrochemical tests revealed the lower corrosion current density, and the positive corrosion potential of multifunctional FEVE@ZnO/TiO2 coating immersion in 3.5 wt% NaCl solution. The experimental results demonstrate that the synergistic effect of organic-inorganic significantly enhances corrosion resistance by retarding the corrosion process and providing active protection against corrosion. The multifunctional coating also exhibits exceptional self-cleaning properties and weatherability when without changing the bronze color and appearance. Consequently, this preparation strategy and research approach for constructing a multifunction coating has a great application prospect in the conservation of bronze relics and metal anti-corrosion.

Construction of chromium-free passivation film of pomelo peel extract on the surface of lithium-ion battery copper foil and study on anti-corrosion mechanism

Passivation treatment is the last key process to ensure the service life of copper foil for lithium-ion batteries. Although chromic anhydride commonly used in industry has an efficient passivation effect, it can threat human health and the environment. Herein, an environmentally friendly passivator is prepared from pomelo peel by a simple and economical solution extraction method, which makes copper foil have good anti-corrosion properties in air, chlorine-containing solution, and organic electrolyte. Electrochemical methods and X-ray photoelectron spectroscopy (XPS) confirm the potential of pomelo peel extractant (PP) to replace chromic anhydride as a passivating agent for copper foil. The interaction mechanism between PP and copper foil is analyzed by adsorption models, and the efficient passivation behavior of PP for copper foil is consistent with the Langmuir model. Density Functional Theory (DFT) calculations of the naringin (main component of PP) is performed to further reveal the protection mechanism of PP on copper foil. In addition, the copper foil treated by PP still has excellent electrochemical performance as lithium-ion battery current collector, indicating that the presence of PP not only protects the copper foil from corrosion, but also does not affect the conductivity of the copper foil. This research provides a new insight into the chrome-free passivation of copper foils, which is in line with the development concept of green production.

Anticorrosion mechanism of epoxy coating containing mesoporous resorcinol-formaldehyde hollow nanosphere loaded with 8-Hydroxyquinolin

Mesoporous resorcinol-formaldehyde hollow nanosphere (MRFHN) with erythrocyte like shape was prepared successfully. The average diameter, shell thickness, and specific area of MRFHN are 223 nm, 42 nm, and 73.2 m2/g, respectively. The average loading capacity of 8-Hydroxyquinoline (8-HQ) in MRFHN is 33 % and the sucked 8-HQ can release continuously from MRFHN. MRFHN loaded with 8-HQ (MRFHN@8-HQ) was introduced into epoxy coating to enhance its anticorrosion performance. The results show that epoxy coating pigmented with MRFHN@8-HQ has a higher anticorrosion performance than neat epoxy coating. Especially, epoxy coating containing 4 wt% of MRFHN@8-HQ presents the best anticorrosion performance and self-healing function, and its coating resistance is still maintained at 109 Ω cm2 even after 50-day immersion in 3.5 wt% NaCl solution. Meanwhile, the scratch on coating surface is covered by a thin layer of 8-HQ which can prevent the AA2024 aluminum alloy from corrosion even after 50-day neutral salt spray test. 8-HQ can release from MRFHN and form a compact inhibiting layer on AA2024 aluminum alloy surface, thus the corrosion of AA2024 aluminum alloy is suppressed effectively. MRFHN@8-HQ can be used as a high performance anticorrosion pigment to give epoxy coating a long term protection.

Unveiling the potency of tetrahydropalmitine as a green anticorrosion material for 2024 aluminum alloy in acid-chloride environments

2024 aluminum alloy has garnered attention from researchers because of its numerous applications in the oil and gas, aerospace, and marine sectors. However, its constituent high Cu content (the primary alloying element) poses a significant challenge to its use, particularly in applications that demand high corrosion resistance. This is particularly troubling in oxygen-containing chloride systems. Herein, we developed a protection strategy for 2024 Al alloy in an acid-chloride environment (composed of 0.5 M NaCl and 0.25 M H2SO4) using natural tetrahydropalmitine (THP) isolated from Corydalis yanhusuo. THP was effectively characterized from its 1H NMR, 13C NMR, and FTIR spectra, and its anticorrosion potentials were methodically investigated by electrochemical, gravimetry and theoretical experiments. Upon the addition of THP to the test system, EIS measurements revealed a steady increase in the Nyquist semicircles, as well as the Bode impedance and phase angle plots, attaining an optimum inhibition efficiency of 91.5 % at 2.0 g/L THP. Tafel plots manifested mixed-type anticorrosion effects with dominant cathodic properties, ascribed to the ordered shielding effect of both the hydrogen evolution reaction and the oxidation of oxide-free ions. According to gravimetric corrosion assessment, the 2024 Al alloy mainly retained its protection over time in the presence of THP, exhibiting only minor decline in its protectability. This is attributed to the combined effect of stable oxide film formation and the adsorbed THP on the alloy surface. SEM afforded the proof of THP adsorption on 2024 Al while XPS offered clarity into its anticorrosion mechanism. Conceptual DFT parameters, molecular electrostatic potential and molecular dynamics simulation were used to comprehend the inhibition process of THP on Al surface. Generally, THP was proven to be a viable and sustainable bio-based anticorrosion material for the protection of 2024 Al alloy.

Study of anti-corrosion epoxy resin coatings with high corrosion resistance and mechanical performance based on quantum dots

The corrosion of steel construction in marine environments faces severe corrosion threats, and coatings based on nanofillers are an effective strategy for steel corrosion protection. However, the related studies of the anti-corrosion coatings based on quantum dots are still poor. In this work, CuS and ZnS quantum dots (QD) were initially synthesized, and epoxy resin (EP) coatings containing QD with ratios of 0.05 wt%, 0.1 wt%, 0.2 wt%, and 0.5 wt% were successfully prepared subsequently. Surface analysis, electrochemical measurements, salt spray tests, and mechanical tensile tests were performed to characterize the prepared quantum dots and study the anti-corrosion behavior and mechanism of the prepared coatings. Results indicated that the prepared CuS and ZnS quantum dots have small sizes with values of 13.8 and 8.9 nm, respectively. Compared to the pure EP coating, QD-EP coatings have a higher mechanical strength and toughness which is conducive to improving the coatings’ corrosion resistance and service life. The impedance values of all the QD-EP coatings increase by more than three orders of magnitude in contrast to pure EP coating after 60 d of testing. Furthermore, the prepared QD-EP coatings possess a long-term anti-corrosion property.

Construction of Smart Coatings Containing Core-Shell Nanofibers with Self-Healing and Active Corrosion Protection.

With increasingly severe metal corrosion, coating preparation with high-performance corrosion protection has attracted more attention. Herein, the encapsulation of the corrosion inhibitor 8-hydroxyquinoline (8-HQ) as well as the self-healing agent linseed oil (LO) in polyvinyl alcohol (PVA) and chitosan (CS) shells were realized by coaxial electrospinning, which was recorded as PVA/CS@LO/8-HQ core-shell nanofibers. PVA/CS@LO/8-HQ nanofibers were employed to promote the high-performance corrosion protection of the epoxy coating. The anticorrosion mechanism was that the change of the local pH on the metal surface stimulated the release of 8-HQ from the nanofibers, which were then chelated with iron ions to form a complex. When cracks occurred and caused rupture of the nanofibers, LO was released and reacted with oxygen to cure them so that the cracks could be healed autonomously. The dynamic potential polarization curves showed that the corrosion inhibition efficiency of the compound inhibitor LO + 8-HQ reached 87.54%, 90.31%, and 85.57% at pH = 3, 7, and 11, respectively, higher than that of the single corrosion inhibitor. Density functional theory calculations revealed that the LO and 8-HQ combination, forming a hydrogen bond interaction, promoted the adsorption of inhibitors on the steel surface. Scanning Kelvin probe and electrochemical impedance spectroscopy proved the self-healing corrosion protection properties of the epoxy coating. These results demonstrated that embedding PVA/CS@LO/8-HQ nanofibers in the coating could obtain self-healing properties, and promote the mechanical and corrosion protection of epoxy coating.

Multi-scale investigation of silane coupling agent for enhanced corrosion resistance in reinforced concrete

Reinforcement corrosion is a significant factor leading to the deterioration of building performance. In order to enhance the serviceability of reinforced concrete under corrosive environments, this study employs a silane coupling agent (γ-aminopropyltriethoxysilane) for steel reinforcement treatment. The anti-corrosion mechanism, crack propagation patterns, and modified corrosion resistance of the steel are investigated at multiple scales. Experimental techniques such as scanning electron microscopy (SEM), X-ray energy-dispersive spectroscopy (EDS), and Fourier-transform infrared spectroscopy (FT-IR) are utilized to explore the influence of the self-assembled coating of the silane coupling agent on the microscopic morphology, elements, and functional groups of the steel. Concrete specimens with treated reinforcement are fabricated, and electrochemical accelerated corrosion tests are conducted to compare corrosion differences among different specimens. Using untreated specimens as a control group, digital image correlation (DIC) technology is employed to capture the full-field strain and displacement distribution during the loading process. The crack propagation and slip behavior at the steel-concrete interface in the composite specimens are analyzed. The research findings indicate that, at the optimal concentration of 1.2 %, the self-assembled coating of the silane coupling agent successfully adheres to the steel surface, significantly enhancing the interfacial abrasion resistance and mechanical strength of the steel-concrete interface, thereby validating the improved corrosion resistance of the steel. This study proposes the self-assembly mechanism and interfacial enhancement mechanism of the silane coupling agent on steel at multiple scales, contributing to a comprehensive understanding of its effectiveness.

Assessment of the Inhibitory Efficacy of a Thiazole Derivative as an Efficient Corrosion Inhibitor for Augmenting the Resistance of MS in Acidic Environments.

Numerous thiazole compounds have been developed as cutting-edge inhibitors because of a rising fascination with using corrosion inhibitors (CIs) and preventative measures to prevent mild steel (MS) from deteriorating. In this study, the ability of a novel thiazole derivative, 2-hydrazono-3-methyl-2,3-dihydrobenzo[d]thiazole hydrochloride (HMDBT), to prevent corrosion of MS (MS) in HCl has been reconnoitered using various approaches, Viz. gravimetric analysis, electrochemical (EC) analysis, and different surface characterizations. With an inhibition efficiency (IE %) of 95.35%, the outcomes elucidate that HMDBT functions as a potent MS CI that is environmentally friendly and sustainable. The computed activation and thermodynamic factors were also employed to better explain the process underpinning the inhibiting tendency of HMDBT. According to the computed values, the HMDBT molecules physically and chemically adhered to the MS surface following the Langmuir model, generating a dense protective layer that may be associated with the presence of a benzene ring and heteroatoms (S & N) in the HMDBT architecture. Based on the findings of the EIS studies, an intensification in the CI's concentration from (50 →800) ppm is ushered by increases in polarization resistance (Rp) from (80.72, 354.31) Ω cm2, and attenuation in double-layer capacitance (Cdl) from (198.78 → 44.13) μF cm-2, respectively, confirming the inhibitory proficiency of HMDBT. The IE of the inhibitor was reported around 95.35% by weight loss measurement and 89.94% through EC measurement. Theoretical analysis including density functional theory (DFT) and molecular dynamics (MD) simulations were carried out to investigate the additional effects of HMDBT on the anticorrosion effectiveness and mechanism of inhibition. The theoretical parameters that were calculated provided important assistance in comprehending the inhibitory mechanism that the CI's moieties disclosed and are in strong concord with experimental methods. To create a "green" inhibitor system, the work presented here provided a potent technique to reduce corrosion by adding a potent new inhibitor.

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

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

Investigation into Effects of Coating on Stress Corrosion of Cable Bolts in Deep Underground Environments.

Due to the intricate and volatile nature of the service environment surrounding prestressing anchoring materials, stress corrosion poses a significant challenge to the sustained stability of underground reinforcement systems. Consequently, it is imperative to identify effective countermeasures against stress corrosion failure in cable bolts within deep underground environments, thereby ensuring the safety of deep resource extraction processes. In this study, the influence of various coatings on the stress corrosion resistance of cable bolts was meticulously examined and evaluated using specifically designed stress-corrosion-testing systems. The specimens were subjected to loading using four-point bending frames and exposed to simulated underground corrosive environments. A detailed analysis and comparison of the failure patterns and mechanisms of specimens coated with different materials were conducted through the meticulous observation of fractographic features. The results revealed stark differences in the stress corrosion behavior of coated and uncoated bolts. Notably, epoxy coatings and chlorinated rubber coatings exhibited superior anti-corrosion capabilities. Conversely, galvanized layers demonstrated the weakest effect due to their sacrificial anti-corrosion mechanism. Furthermore, the effectiveness of the coatings was found to be closely linked to the curing agent and additives used. The findings provide valuable insights for the design and selection of coatings that can enhance the durability and reliability of cable bolts in deep underground environments.