Corrosion Protective Coatings Research Articles

Fabrications of hybrid Polyurethane-Pd doped ZrO2 smart carriers for self-healing high corrosion protective coatings

The work demonstrates the effective utilization of hybrid Polyurethane - palladium doped zirconium oxide (Pd–ZrO2) as innovative carriers for corrosion protection coatings on steel materials. ZrO2 and Pd–ZrO2 nanoparticles were successfully synthesized using Photodeposition followed by the hydrothermal synthesis method. The synthesized nanoparticles were then incorporated into the polyurethane matrix and characterized using Fourier-transform infrared spectroscopy and scanning electron microscopy (SEM). The FTIR and SEM confirm the presence of ZrO2 and Pd–ZrO2 nanoparticles and their morphologies in polyurethane composites material. The thermogravimetric analysis (TGA) results indicated that the polyurethane matrix remained stable up to 250 °C. At 800 °C, >50% of residues are observed for Pd–ZrO2 – polyurethane in the TGA analysis, which confirms that the primer and nanoparticles addition enhances the thermal stability of the composite. The water contact angle measurement explains the hydrophobic behavior of nanocomposite modified coatings on a mild steel substrate. It indicates that Pd–ZrO2 and primer significantly increase the hydrophobicity of polyurethane. The major advantages of developing water-repellent or hydrophobic surfaces open up a world of possibilities for metals and alloys in terms of corrosion prevention. Electrochemical impedance spectroscopy (EIS) and a salt spray test were used to determine the anti-corrosion behavior of the prepared polymer nanocomposites. The polymer nanocomposite coatings have better anti-corrosive capabilities when compared to pure polyurethane. The corrosion protection efficiency increased from 76.63% to 97.57% upon incorporating 2 wt % of Pd–ZrO2 in the polyurethane matrix. The results confirmed that the modifications on the polyurethane enhanced the hydrophobicity and anti-corrosion properties of the polymer nanocomposite coatings.

Tannic acid reinforced sol-gel silica coatings for corrosion protection of zinc substrates

Silica (SiO2) coatings are a widely discussed inorganic coating alternative, offering a feasible and simple method of passive corrosion protection, with the option of enhancement by incorporating different inhibitors into the matrix. The novelty of the present study lies in the reinforcement of the sol-gel SiO2 coating system, by the addition of different tannic acid (TA) amounts in the sol phase and producing nano scale coatings by dip-coating technique, on Zn. Tannic acid is a non-toxic substance, which acts as anodic corrosion inhibitor. Long term corrosion measurements were carried out to check the durability and corrosion resistance of the thin coatings. They were characterized by Electrochemical Impedance Spectroscopy and Potentiodynamic polarization curves, as well as by physical methods (SEM, contact angle and adhesion measurements). The pseudo-porosity of the coatings was also evaluated. It has been concluded that SiO2 coatings containing TA in an optimal concentration show lower corrosion current densities than simple SiO2 coatings, good adhesion to the zinc substrate, and lower porosity. The interactions occurring between the SiO2 and TA put in evidence by FT-IR, Raman spectroscopy offer an explanation of the better corrosion behavior of the SiO2+TA coating compared to the pure SiO2.

Al alloy protection via ultra-thin ceramic coatings and different surface pretreatments

The efficiency of ultra-thin corrosion protection coatings for susceptible to local corrosion AA2024-T3 is demonstrated. For this purpose, with atomic layer deposition (ALD) 50 nm thick TiO2, Al2O3, an Al2O3-TiO2 mixture and Al2O3/TiO2 nanolaminate coatings are grown on AA2024-T3 substrates, receiving different pretreatments prior to ALD coating. One pretreatment involves polishing and cleaning with organic solvents, and the second utilizes an additional low-potential electrochemical treatment in sulfuric acid. The samples are characterized with scanning electron microscopy, scanning transmission electron microscopy, wavelength-dispersive X-ray fluorescence spectroscopy, X-ray diffraction and reflection, and nanoindentation and are tested using linear sweep voltammetry, electrochemical impedance spectroscopy, and immersion in a salt solution. The study shows that ultrathin metal oxide coatings applied via ALD can significantly enhance the corrosion resistance of Al alloys, and the performance depends on the pretreatment of the alloy, as well as on the material/structure of the coating. The best ultrathin coating with less than 100 nm thickness withstood well 1000 h immersion test.

Recent Trends in Waterborne and Bio‐Based Polyurethane Coatings for Corrosion Protection

AbstractPolyurethanes (PUs) have been extensively exploited for the production of protective coatings thanks to the versatility of their chemistry, which allows to adjust the coating properties depending on the final application. In the last decade, the concerns on the negative impact on the environment and human health of traditional petroleum‐based and solvent‐borne PUs have fostered the research on more environmentally friendly alternatives. This review article provides an overview of the recent approaches that have been profitably pursued for the development of green PUs coatings for the protection of metal surfaces from corrosion. In particular, waterborne and bio‐based polyurethane coatings are addressed, highlighting the main strategies adopted to enhance their anticorrosion ability. Finally, relevant data on the protective performances of green PU coatings are collected and critically discussed.

Performance of Three Magnesium-based Coatings for Corrosion Protection of Concrete against Sulfuric Acid

Performance of Three Magnesium-based Coatings for Corrosion Protection of Concrete against Sulfuric Acid

Nanocomposite organic coatings for corrosion protection of metals

Nanocomposite organic coatings for corrosion protection of metals

Nanostructured Poly(methyl Methacrylate)–Silica Coatings for Corrosion Protection of Reinforcing Steel

In the absence of preventive maintenance, corrosion of structural steel by the deterioration of the passive layer due to exposure to aggressive environments is the main failure factor of reinforced concrete. To overcome economic, safety, and environmental implications, present research efforts focus on eco-friendly organic–inorganic hybrid coatings to achieve effective protection of reinforcing steel. Nanostructured PMMA (poly(methyl methacrylate))–silica coatings developed by combining reactions of the polymerization of methyl methacrylate and 3-[(methacryloxy)propyl]trimethoxysilane with the sol–gel hydrolytic condensation of tetraethyl orthosilicate using isopropanol as a solvent represent a promising approach to accomplish this goal. The nanoscale dispersion of silica nodes covalently conjugated with PMMA chains led to transparent, homogeneous, and pore-free coatings deposited with a thickness of 15 μm on 2D and 3D reinforcing steel. Mechanical, thermal, and surface analyses showed a strong adhesion of the coating to the substrate surface (15.9 MPa), a thermal stability of up to 256 °C, and a contact angle of about 75°. Electrochemical assays in standard 3.5 wt % NaCl solution, simulated carbonated, and alkaline concrete pore solutions confirmed effective corrosion protection, with an impedance modulus of up to 100 GΩ cm2 (at 4 mHz) and a lifetime of more than 670 days. Hence, PMMA–silica hybrid coatings are an eco-friendly and efficient alternative to protect reinforcing steel against corrosion, helping to prevent structural failures and fatal accidents.

Silicon carbide/enamel composite coatings for steel corrosion protection: Microstructure, thermal expansion behavior, and anti-corrosion performance

Vitreous enamel coating has been utilized to protect metallic substrates against corrosion and has proven to be effective. Herein, a new low-temperature sintering silicon carbide/enamel composite coating was produced and compared to pure enamel coating. The microstructure, thermal expansion behavior, and anti-corrosion performance of the prepared coatings were evaluated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), dilatometric test, and electrochemical measurements (open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), and linear polarization resistance (LPR)). The results indicated that the composite coatings had gradually matched thermal expansion with the steel substrate due to the inclusion of silicon carbide and the raised porosity, which further resulted in the reduction of residual stress and the eradication of surface microcracks. The microstructural alterations increased the anti-corrosion effectiveness of composite coatings, according to the early electrochemical testing (at 24 h). Particularly, the polarization resistance (Rp) of a composite coating containing 7.5 wt% silicon carbide addition was found to be 20 times greater than that of the pure enamel coating. These results imply that the silicon carbide/enamel composite coating outperforms the pure enamel coating and can provide effective corrosion protection for steel.

UV-cured electroactive polyurethane acrylate coatings with superhydrophobic surface structure of biomimetic peacock feather for anticorrosion application

In this work, UV-cured electroactive polyurethane acrylate (EPU) materials with the superhydrophobic surface structure of biomimetic peacock feather were firstly prepared and applied in anticorrosive coatings. Firstly, amine-capped aniline trimer (ACAT) and vinyl-capped aniline trimer (VCAT) were synthesised and characterised by 1H-nuclear magnetic resonance spectroscopy (NMR), Fourier transform infrared spectroscopy (FTIR) and mass spectroscopy. Polyurethane acrylate (PUA) was synthesised and characterised by 1H NMR and FTIR spectroscopy. EPU was then prepared through the UV curing of PUA with 0, 1, 3 and 5 wt% VCAT (named EPU0, EPU1, EPU3 and EPU5, respectively) and characterised via FTIR. The redox capabilities of the as-prepared EPU series were investigated by cyclic voltammetry studies. EPU with higher VCAT loading (EPU5) exhibited better corrosion protection performance than those with lower VCAT loadings (EPU0, EPU1 and EPU3) based on a series of electrochemical corrosion measurements because of the formation of a dense metal oxide layer as evidenced by Raman spectroscopy. Moreover, EPU5 with the surface structure of biomimetic peacock feather (denoted by BEPU5) was prepared by nanocasting technique with polydimethylsiloxane as the flexible transparent negative template. The surface morphology and wettability of BEPU5 was investigated by scanning electron microscopy and contact angle (CA) analysis. The CA of BEPU5 remarkably increased to 145° compared with that of EPU5 63°. This massive increase in CA indicates efficient superhydrophobic properties, which were induced by the biomimetic peacock feather and produced outstanding corrosion protection performance for short and long terms based on a series of electrochemical corrosion measurements. This study is the first of its type to produce a biomimetic feather with massive increase in superhydrophobic properties, which is expected to revolutionise biomimetic industrial coating technologies towards better corrosion protective coatings.

First-principles calculations of O-atom diffusion on fluorinated graphene

Fluorination of graphene is one of the most effective methods to improve the corrosion protection of graphene coatings. In this work, the diffusion and penetration behaviors of O atoms on fully fluorinated graphene (CF) and partially fluorinated graphene (C<sub>4</sub>F) are investigated by using the method of searching for NEB transition state . The effects of F atoms on the corrosion resistance of fluorinated graphene films are also analyzed <i>r</i>. The results show that the adsorption of F atoms can effectively inhibit the diffusion of O atoms on graphene. On C<sub>4</sub>F, the F atoms are distributed in a para-top position, which greatly increases the surface diffusion energy barrier of O atoms. Moreover, it is difficult for the adsorbed O atoms to diffuse to different sp<sup>2</sup> C rings through the obstruction of F atoms. The energy barrier of the horizontal diffusion of O atoms even reaches 2.69 eV in CF. And with the increase of F atoms, the stable structure of graphene is gradually destroyed, the ability of C-atom layer to bar the penetration behaviors of O atoms decreases greatly. Furthermore, the interfacial adhesion work of pure graphene, CF and C<sub>4</sub>F films with Cu(111) surfaces are calculated, as well as the electronic structures of the composite interface are investigated by using first-principles calculations. The interfacial adhesion work of the Cu/G, Cu/C<sub>4</sub>F and Cu/CF interfaces are 2.626 J/m<sup>2</sup>, 3.529 J/m<sup>2</sup> and 3.559 J/m<sup>2</sup>, respectively. The calculations show that the bonding of C<sub>4</sub>F and C<sub>4</sub>F with Cu substrate are stronger than pure graphene with Cu substrate, and the interfacial adhesion work increases with the augment of F atom adsorption concentration. The calculation of the density of states also conforms that the interaction between Cu and C atoms of the Cu/C<sub>4</sub>F interface is stronger than that at the Cu/CF interface. Bader charge analysis shows that the charge transfer at the Cu/C<sub>4</sub>F interface and the Cu/CF interface increase comparing with that at the Cu/G interface, and Cu/C<sub>4</sub>F interface has more charge transfer, in which Cu—C bonds are formed.

Recent advances in epoxy coatings for corrosion protection of steel: Experimental and modelling approach-A review

Steel is known for its high mechanical strength, low cost of fabrication and hence widely used for ship building, offshore structures, pipelines and drilling equipment. Corrosion of steel is pricey problem in many fields specially in marine environment and oilfields which are better known for high pressure, high temperature and corrosive conditions. According to International Zinc Association (IZA), India loses around 5–7% of its Gross Domestic Product (GDP) every year due to corrosion [1].Polymer coatings have been regarded to be the most efficient and economic approach to retard the metal corrosion. Epoxy have been recognized as an effective anticorrosion coating material in both scientific communities and industries as it provides good barrier properties, but after curing, microcracks appear in the epoxy coatings which permit penetration of aggressive ions through the epoxy layer. To overcome this shortcoming, epoxy coatings are modified with nanomaterials. Nanomaterials based epoxy coatings have good adhesion to metals, high corrosion resistance, elastic stability, and high durability in corrosive environment. The intermolecular interaction plays a very important role in nanocomposite polymer coatings to decide adhesion of coatings over metal surface which ultimately determines its corrosion protection. Therefore, In the current review, we will highlight the experimental and computational approaches of these high – performance polymer nanocomposite as anticorrosive coating materials over steel substrate.

Long-term corrosion protection of styrene acrylic coatings enhanced by fluorine and nitrogen co-doped graphene oxide

Graphene materials are widely used as a physical barrier when applying anticorrosion polymer coatings due to their large surface area and layered structure. However, the electrical conductivity of intrinsic graphene can accelerate galvanic corrosion and shorten the protection period. In this work, fluorine and nitrogen co-doped graphene oxide (FNGO) was synthesized by a hydrothermal process and acted as an anticorrosion filler in waterborne styrene acrylic coatings. Styrene acrylic coatings with 0.4 wt% FNGO showed a corrosion current density that was two orders of magnitude lower than the other samples in the potential polarization test and the largest impedance modulus in the electrochemical impedance spectroscopy results. The outstanding corrosion protection was attributed to the graphene acting as a physical barrier and the synergistic effect of the doped fluorine and nitrogen. In addition to the ‘labyrinth effect’ of the graphene matrix, the nitrogen atoms inserted in the graphene plane and fluorine atoms grafted on the graphene simultaneously adjusted the electrical properties of graphene, prohibiting electron transport between it and the styrene acrylic resin matrix. This result indicates that doped graphene oxide has great potential to increase the corrosion resistance of waterborne coatings.

Self-healing Organic Coatings Based on Microcapsules – A Patent-based Review

: Self-healing coatings are intended to increase long-term durability and reliability and can be prepared by the use of microcapsules containing a self-healing agent capable of interacting with the matrix and regenerating the system. This review article provides an overview of the stateof- the-art patents published in the field of microcapsule-based self-healing organic coatings since the early 2000s. A discussion regarding coatings for corrosion protection is presented and the different self-healing approaches and mechanisms are also addressed, as well as future challenges and expectations for this kind of coatings.

Corrosion protection coatings embedded with silane-functionalized rGO/SiO2 nanocontainers: Enhancing dispersive and corrosion-inhibitor loading capabilities

Taking advantage of the excellent barrier properties of reduced graphene oxide (rGO) sheets and the loading capacity of mesoporous silica (SiO2), silane-functionalized rGO/SiO2 nanocontainers are synthesized and, after loaded with benzotriazole (BTA), composite corrosion protection coatings are prepared. The XRD, FTIR, XPS, SEM, and TEM are used to confirm the successful preparation of silane-functionalized rGO/SiO2 nanocontainers, and BET and UV–visible measurements are used to estimate the loading and release behavior of BTA. Dispersion stability of the nanocontainers is observed, the surface morphology, wettability, and water absorption of coatings are characterized by SEM, water contact angle, and weight method, respectively. The corrosion behavior of pristine and scratched composite coatings is characterized by EIS, the effect of released BTA is further confirmed. The results show that silane-functionalized rGO/SiO2 nanocontainers possess excellent dispersibility and load capacity, reduce defects and micropores in composite coatings, and provide improved permeability resistance, corrosion resistance, and self-repairing performance.

Corrosion protection of benzoxazine and cardanol-doped polyaniline coatings

Corrosion protection of benzoxazine and cardanol-doped polyaniline coatings

Advances and future outlook in epoxy/graphene composites for anticorrosive applications

Coatings are the prevailing, practical and preferred way to safeguard metals from corrosion. Graphene based organic polymer coatings are extensively used as corrosion fortification aids in this era. This short review highlights the importance of diverse features of such engineered coatings. Graphene has engrossed momentous responsiveness in many industrial fields due to its superior anti-corrosion and barrier properties. The current review honestly debated the recent works and reports on epoxy/graphene coatings for metal protection from extensive corrosion and oxidation. The various methodologies to acquire stable-homogenous graphene/epoxy dispersion, covalent functionalization of graphene, doping of graphene with other nanofillers and their effect on corrosion protection of epoxy/graphene coatings along with detailed corrosion protection mechanism are discussed. This review also outlines the integration of potentially relevant multifunctionalities in epoxy/graphene coatings for self-healing, antifouling, self-cleaning and corrosion protection with suitable examples.

Composite Materials from Renewable Resources as Sustainable Corrosion Protection Coatings.

Epoxidized linseed oil (ELO) and kraft lignin (LnK) were used to obtain new sustainable composites as corrosion protection layers through a double-curing procedure involving UV radiation and thermal curing to ensure homogeneous distribution of the filler. The crosslinked structures were confirmed by Fourier-transform infrared spectrometry (FTIR), by comparative monitorization of the absorption band at 825 cm−1, attributed to the stretching vibration of epoxy rings. Thermal degradation behavior under N2 gas indicates that the higher LnK content, the better thermal stability of the composites (over 30 °C of Td10% for ELO + 15% LnK), while for the experiment under air-oxidant atmosphere, the lower LnK content (5%) conducted to the more thermo-stable material. Dynamic-mechanic behavior and water affinity of the new materials were also investigated. The increase of the Tg values with the increase of the LnK content (20 °C for the composite with 15% LnK) denote the reinforcement effect of the LnK, while the surface and bulk water affinity were not dramatically affected. All the obtained composites were tested as carbon steel corrosion protection coatings, resulting in significant increase of corrosion inhibition efficiency (IE) of 140–380%, highlighting the great potential of the bio-based ELO-LnK composites as a future perspective for industrial application.

Self-Healing Coatings for Corrosion Protection: The Importance of the Transport of Active Agents from the Coating Towards the Defect

In so called smart or intelligent self-healing coatings active agents that are safely stored inside the coating are released upon onset of corrosion. This release is triggered by a suitable trigger signal that should be a safe indicator for the onset of corrosion and its continuation. Different from the current standard where release from pigments occurs via leaching, the safe storage should ensure that there is no uncontrolled release of the active agents when they are not needed for inhibiting corrosion and restoring protection. While there are many studies on different concepts for storage and active release triggered by corrosion, achieving an efficient transport of the released agents to the defective site(s) is a likewise crucial but so far widely neglected issue. Recently it was proposed that the signal spreading from the defect into the coating can be significantly enhanced by the use of layers of conducting polymer, such as polypyrrole, applied as an intermediate layer between the metal substrate and the organic coating. In that case the decrease in potential is the signal that is spread. Here, we will show that by such polypyrrole layers also the transport of active agents can be significantly enhanced. To enable a fundamental in-depth study of the mobility of active agents from the coating towards the defective site, a dedicated experimental model set-up was designed especially for the study of ions transport. The main question to be addressed was whether the main transport will be along the metal│PPy interface or rather through the matrix of the reduced polypyrrole. Zinc was chosen as metallic substrate, owing to its importance in galvanized steel products. The corrosion potential at the defective site was used as a measure for the amount of corrosion inhibitor released into the defect and hence as a measure to reflect the ionic transport and self-healing efficiency of the coating by different corrosion inhibitors. The progress of polypyrrole reduction, in turn, was monitored by use of Scanning Kelvin Probe (SKP) for recording the change of potential as a function of distance from the defect and of time. The concentration of corrosion inhibitor at the defective site was also quantified using ICP-MS (OES) analysis of the solution in the defect at different times. In order to ensure for reliable quantification of the transport that released corrosion inhibitor moving towards the defect is not reacting with corroding metal at the interface special PVB│PPy│Au-Glass model samples were utilized. The results indicate that Ce4+ is more effective than Ce3+ for reaching and passivating the defect. In addition, organic corrosion inhibitors (8-HQ, β-CD and L-Car) were found to be highly efficient in inhibiting the defective site. This is proposed to be due through a synergistic mechanism, which is based on an interaction of the passivating effect of these corrosion inhibitors and the passivating effect of polypyrrole. The synergistic mechanism shows astonishing passivation effects, resulting in anodic potential shifts of the corrosion potential of more than 600 mV. Concerning the main path for ionic transport, it was found that this occurs mainly through the matrix of the (partially) reduced polypyrrole. Hence, the transport of positive ions should be favored compared to the one of negative ions.

Effect of Microstructure and the Interface on Localized Corrosion in Metallic Nitride Coated Metallic Flow Field Plate in Simulated Low-Temperature Fuel Cell Conditions

Proton Exchange Membrane (PEM) fuel cell offers clean energy on par with renewable energy generations. Graphite bipolar plate, engraved with flow field which is a key component in the PEMFC assembly suffers from volumetric and machining issues. Metallic plate is as an alternative, among which stainless steel and titanium are looked upon as promising candidates, but it suffers from the aspect of corrosion. Inherent corrosion current density (Icorr) of SS316L is 0.5 µA/cm2 which is well within the international standards (Department of Energy (DoE), US) but that of Ti-6Al-4V is 47 µA/cm2 which is not meeting the DoE targets under hydrogen purge conditions. Under fuel cell operating conditions, both the material tends to fail due to corrosion aspects. Various surface treatments are imparted to enhance corrosion in the PEMFC environment, but most of the corrosion protection coatings fail over a period of time due to various aspects.An in depth understanding of the microstructure of the coating prior and post, subjecting it to simulated fuel cell conditions and study of the interface will elude failure at earlier stages of real time operation. In this study, local investigations were carried out on metallic nitride coated SS316L flow field plate to juxtapose the changes induced in the microstructure due to change in pH of the simulated electrolyte, the effect of the interface on the adhesion of the coating. Titanium nitride particles (as seen in Fig.1) adhered to the base material and qualified with 5B rating in ASTM D3359 adhesion studies. Pre-processing and post-processing treatments resulted in the roughness of the coating (Ra) as low as 11nm. Corrosion current density of the coated specimen, Icorr is 0.455 µA/cm2, is within DoE target values and the Ecorr was positive, thus enhancing the corrosion resistance fuel cell operating conditions. Localized corrosion studies reveal the role of pitting agents, present in the simulated electrolyte, which enhance the mechanical cracking of coating layer thus undermining the durability of the coating when tested over a period of 6 months. Figure 1

Thermally Assisted Machine Hammer Peening of Arc-Sprayed ZnAl-Based Corrosion Protective Coatings

Structural elements of offshore facilities, e.g., offshore wind turbines, are subject to static and dynamic mechanical and environmental loads, for example, from wind, waves, and corrosive media. Protective coatings such as thermal sprayed ZnAl coatings are often used for protection, mainly against corrosive stresses. The Machine Hammer Peening (MHP) process is an innovative and promising technique for the post-treatment of ZnAl coating systems that helps reducing roughness and porosity and inducing compressive residual stresses. This should lead to an enhancement of the corrosion fatigue behavior. In this paper, the effect of a thermally assisted MHP process was investigated. The softening of the coating materials will have a direct effect on the densification, residual porosity and the distribution of cracks. The investigation results showed the influence of thermally assisted MHP on the surface properties, porosity, residual stresses, and hardness of the post-treated coatings. The best densification of the coating, i.e., the lowest porosity and roughness and the highest compressive residual stresses, were achieved at a process temperature of 300 °C. A further increase in temperature on the other hand caused a higher porosity and, in some cases, locally restricted melting of the coating and consequently poorer coating properties.