Corrosion Protective Coatings Research Articles

Polyester-Based Coatings for Corrosion Protection.

The article is the first review encompassing the study and the applications of polyester-based coatings for the corrosion protection of steel. The impact of corrosion and the challenges encountered thus far and the solutions encountered in industry are addressed. Then, the use of polyesters as a promising alternative to current methods, such as phosphating, chromating, galvanization, and inhibitors, are highlighted. The classifications of polyesters and the network structure determine the overall applications and performance of the polymer. The review provides new trends in green chemistry and smart and bio-based polyester-based coatings. Finally, the different applications of polyesters are covered; specifically, the use of polyesters in surface coatings and for other industrial uses is discussed.

Graphene-Dominated Hybrid Coatings with Highly Compacted Structure on Stainless Steel Bipolar Plates.

Highly conductive corrosion protection coatings are necessary for metallic bipolar plates (BPs) of the proton-exchange membrane fuel cell. Graphene coatings have the potential of protecting metal substrates from corrosion without obscuring their excellent electrical conductivity. The electron transfer in the coatings facilitates the formation of galvanic cells, so the challenge is to block the mass transfer of the corrosion process. Here, we constructed highly compacted hybrid coatings with aligned water-dispersible graphene layers. The water-dispersible graphene (SG) held an electrical conductivity of >270 S cm-1 while providing an unprecedented dispersibility, which can be redispersed from filter cake with a concentration of 120 mg mL-1 or even dry state. The cohesion of the hybrid coatings was attributed to the interaction between highly aligned SG layers and the heterointerface between SG and polydopamine (PDA), as proven by the molecular dynamics simulations. The hybrid coatings presented a corrosion current density of 0.023 μA cm-2 and an interfacial contact resistance of 9.94 mΩ cm2, which meets the requirements of corrosion protection and electron transfer for the coatings on metallic BPs. The water-based fabrication method of the graphene-dominated hybrid coatings was a promising alternative of the vacuum-based deposition method for industrial production.

Multi-Elemental Coatings on Zirconium Alloy for Corrosion Resistance Improvement

Zirconium alloys are commonly used as a cladding material for fuel elements in nuclear reactors. This application is connected with zirconium alloy’s good resistance to water corrosion and radiation resistance under normal working conditions. In the case of severe accident conditions, the possibly very fast oxidation of zirconium alloys in steam or/and air atmosphere may result in the intense generation of hydrogen and explosion of the hydrogen oxide mixture. The development of a solution to minimize the aforementioned risk is of interest. One of the actual concepts is to improve the oxidation resistance of Zr alloy cladding with protective coatings. This study aimed to develop, form, and investigate new coatings for zirconium alloy Zry-2. Multi-elemental Physical Vapour Deposition (PVD) coatings with Cr, Si, and Zr were considered for Institute of Nuclear Chemistry and Technology) INCT as corrosion protective coatings for nuclear fuel claddings. Heat treatment at 850–1100 °C/argon, air oxidation processes at 700 °C/1–5 h, and a long-term corrosion test in standard conditions for Pressure Water Reactor (PWR) reactors (360 °C/195 bar/water simulating the water used in PWR) were carried out. Initial, modified, and oxidized materials were characterized with Scanning Electron Microscopy (SEM) (morphology observations), Energy Dispersive Spectroscopy (EDS) (elemental composition determination), and X-ray Diffraction (XRD) (phase composition analysis). Slower oxidation processes and a smaller oxidation rate, in the case of modified material investigations, were observed, as compared with the unmodified material. The obtained results displayed a protective character against the oxidation of formed layers in the defined range of parameters in the process.

Corrosion and tribocorrosion protection of novel PEO coatings on a secondary cast Al-Si alloy: Influence of polishing and sol-gel sealing

PEO coatings have been developed on a secondary cast Al-Si alloy, using a novel aluminate-based electrolyte, containing Na4P2O7, Na2WO4 and K2TiF6. The protective performance of the PEO coatings has been improved throughout the application of two post-treatments: polishing of the outermost coating layer and sealing with a sol-gel layer. While the sol-gel has notably improved the corrosion resistance and dielectric properties, due to the sealing of surface pores, the decrease in surface roughness achieved by polishing have enhanced the tribocorrosion performance. The post-treatments studied would enable the future application of PEO coatings on components with high requirements in corrosive environments.

Bio-inspired coatings for corrosion protection

Bio-inspired coatings for corrosion protection

Self-Healing Corrosion Protection Coatings Obtained by Anodization and Sol–Gel Process on Mg AZ31 Alloy

Self-Healing Corrosion Protection Coatings Obtained by Anodization and Sol–Gel Process on Mg AZ31 Alloy

Parabolic Model for Optimum Dry Film Thickness (DFT) of Corrosion Protective Coatings

This study proposes a model for calculating the optimum dry film thickness of corrosion protective Coatings. It was assumed that the graph of coating thickness against corrosion rate is a parabola whose coordinates at turning point consists of optimum thickness and minimum corrosion rate. On this basis, equation of parabola was formed. Three equations of parabola were also formed with three assumed thicknesses, taking arbitrarily with their corresponding corrosion rates of the coated metals. From the equations, a 3x3 matrix was derived. From the solution of the matrix, equations for optimum thickness, minimum corrosion rates and corrosion rate of uncoated specimen were obtained. It is assumed that with this model a technical ground shall be established, upon which the optimum thicknesses of corrosion protective coatings shall be recommended.

Cerium-based conversion films developed on LiAl-layered double hydroxide coatings for corrosion protection of AA7075 aluminum alloys

The paper presents several experimental results regarding the influence of various procedures applied to incorporate Ce species in hydrotalcite–type chemical conver­sion coatings on the overall corrosion performance for AA 7075 aluminum alloy as a metallic substrate. Two routes were envisaged: (i) chemical incorporation of Ce by immersion in cerium nitrate solutions and (ii) electrochemical deposition of hydro­phobic Ce - based layer involving ethanolic solutions of stearic acid and cerium nitrate. The chemical route involving immersion in cerium nitrate solutions led to the incorpo­ration of 2.46 – 6.84 wt.% Ce in the composition of the porous conversion layer. The electrochemical process facilitated the formation of a hydrophobic cerium stearate layer on porous hydrotalcite conversion coating showing water contact angles of about 132o and a higher Ce content incorporated of 6.55 – 9.73 wt.%. The corrosion performance of the Ce-based conversion coatings is also discussed.

Recyclable vitrimer epoxy coatings for durable protection

In this research, the synthesis and application of vitrimer epoxy coatings for long-term corrosion protection of metal surfaces are described. To that end, a polyamine curing agent based on vinylogous urethanes (VUs) was developed to add repairability, recyclability and recoatability to thermosetting materials. Thin films with excellent resistance to water penetration and damage could be obtained by combining the dynamic hardener with existing epoxy resins, resulting in good barrier properties. Various formulations were investigated yielding transparent coatings with durable corrosion protection, even after being scratched, exposed to saltwater, and subjected to steam condensation. Furthermore, stress-relaxation experiments revealed sufficient material flow at 150 °C, which could be significantly slowed down below 100 °C. Optical microscopy was used to demonstrate the healing ability of the vitrimer coatings, resulting in the restoration of barrier properties after scratching. The dynamic properties of the epoxy resin were used to recoat an aluminium plate as a proof of concept, demonstrating that the thin layer could be adhered to a surface again in its cured state. As a result, the service life of epoxy coatings and protected metals could be extended while maintaining excellent mechanical properties, opening the door to a wide range of potential applications such as marine coatings and concrete bonding.

Corrosion Protection of Phosphate Conversion Coatings to Carbon Steel in the Presence of Bacterial Biofilms

Abstract Despite its relatively limited corrosion resistance, carbon steel is one of the most widely used engineering materials. An effective technique to improve its corrosion resistance, particularly during transport and storage, is phosphating. On the other hand, it is well known that different environmental bacteria can grow and develop on metal surfaces, forming biofilms. Some of those bacteria are capable of solubilizing phosphate. The objective of this work was to evaluate the stability of iron and manganese phosphate conversion coatings applied on SAE 1010 carbon steel in the presence of biofilms for two environmental bacterial strains: Pseudomonas aeruginosa and Paenebacillus sp. Both strains are biofilm-forming and phosphate solubilizing bacteria. Electrochemical techniques complemented with surface observation by scanning electron microscopy were applied. The electrochemical results showed that, although the presence of a bacterial biofilm in most cases produced a decrease in the corrosion rate, they provoked a shift of the pitting potential to more active values. This shift led to narrower passive zones, compromising the protection provided by the phosphate conversion coating to the 1010 SAE carbon steel by facilitating the onset of localized corrosion. The degree of the compromise of passivity was dependent on the coating and the bacterial strain. P. aeruginosa biofilms were more detrimental for both coatings than the Paenabacillus sp. biofilms. Thus, it is important to point out that to maintain the corrosion protection imparted by phosphate conversion coating to carbon steel, it is necessary to avoid the development of biofilms on the coated surface.

Electrodeposition of Amorphous Molybdenum Oxide on Iron-Group Element Based Plating and its Novel Application as a Corrosion Protective Coating

The corrosion resistance of materials composed of metal is an essential property for preventing material deterioration caused by corrosion. In this study, we demonstrate that corrosion resistance can be significantly improved through the electrodeposition of molybdenum oxide onto a metal plating containing iron-group elements. Mo oxide can be electrodeposited using a simple plating bath, low current density, and short deposition time, exhibiting a fascinating metallic gloss appearance. GI-XRD and XPS analyses revealed that amorphous Mo oxide adhered to the substrate by a seed layer partially reduced to metallic Mo by the iron-group element in the substrate, based on the principle of “induced co-deposition.” A Mo oxide coating with a thickness of approximately 100 nm decreases the corrosion current density of Ni-W plating by approximately 5 times and the passivation current density by approximately 10 times in a 3 mass% NaCl solution. Mo oxide coatings represent an attractive strategy for improving the corrosion resistance of various metal materials containing iron-group elements.

Active anticorrosion and self-healing coatings: A review with focus on multi-action smart coating strategies

• Recent trends in active anticorrosion protective coatings are summarized. • Self-healing coatings as defect closing routes for metal protection are reviewed. • Functionalities and multi-action mechanisms in multifunctional coatings are discussed. The development of smart coatings with potential for active anticorrosion and self-healing protection of metals is essential for long-term performance of metallic structures in aggressive chemical environments. Presently, emphasis has been placed on the development of advanced smart coatings for corrosion protection in different applications. Innovative multifunctional coatings with fascinating stimuli-responsive functionalities are considered “smart”. The stimuli-responsive functionalities of these smart coatings when properly harnessed result in a class of coatings with inherent autonomous control of corrosion. Fundamentally, when metals are exposed to aggressive environments, occurrences at the metal-solution interface cause environmental changes. These changes can be controlled when triggers from external environment set off active components of smart coating, thereby enhancing coating's life and functionality. Common triggers include the availability of moisture, concentration of chloride ion, pH gradient, mechanical damage, impact, fatigue, light, redox activity and temperature. In this review, recent technological trends in active anticorrosion and self-healing coatings as functional routes for metal protection are summarized, stimuli responsiveness and mechanisms of inhibition are discussed, and recent multi-action protective systems are particularly focused on.

Capped inhibitor-loaded halloysite nanoclay-based self-healing silica coatings for corrosion protection of mild steel

The effect of polymeric nanocapsule capping in benzotriazole encapsulated into halloysite nanoclay (HNTs) dispersed into hybrid silica coatings was investigated for corrosion protection of mild steel. Optimization of the amount of inhibitor-loaded halloysite nanotubes with and without capping in the coating sol was carried out. The prepared formulations were dip-coated on mild steel substrates using dip-coater and then cured at 130 °C for 1 h. Surface morphology and elemental analysis of the nanoclay were studied using scanning electron microscopy and energy dispersive X-ray spectroscopy. X-ray diffraction and Fourier Transform Infrared spectroscopy analyses were carried out to confirm the encapsulation and capping of the halloysite nanoclay. The anti-corrosion and autonomic-healing properties of bare and coated substrates in 3.5 wt% NaCl solution were studied using electrochemical impedance spectroscopy, potentiodynamic polarization measurements and scanning vibrating electrode technique for varying exposure times. The coatings generated from the capped inhibitor-loaded HNTs dispersed sol-gel matrix was seen to provide higher corrosion resistance when compared to uncapped HNT based silica coatings. Electrochemical studies carried out for capped inhibitor-loaded HNT based coatings have shown an increase in charge transfer resistance to 108 Ω cm2 from 106 Ω cm2 of uncapped inhibitor-loaded HNT based coatings.

Large-scale prepared superhydrophobic HDTMS-modified diatomite/epoxy resin composite coatings for high-performance corrosion protection of magnesium alloys

Superhydrophobic coatings have great potential applications in protecting metallic substrates due to their excellent water-repellency and high corrosion resistance, however, most of their preparation processes are complicated, expensive and difficult to scale up for practical applications. Herein, we reported a facile, low-cost and large-scale-preparation method to fabricate superhydrophobic coatings on the magnesium alloy, of which superhydrophobic hexadecyltrimethoxysilane (HDTMS)-modified diatomite powder was first synthesized by electrochemical deposition method, and subsequent spray coating of the epoxy resin and superhydrophobic diatomite mixture was performed to form superhydrophobic composite coatings on the alloy substrates. The influencing factors of surface wettability of the modified diatomite were comprehensively investigated. Under the optimized synthesis condition of a current density of 0.033 A·cm−2 and electrodeposition time of 2.5 h, the superhydrophobic diatomite powder had an approximately 260 % (in mass fraction) production yield. The spray-coated composite coating delivered superior superhydrophobicity with water contact angle of circa 157° and self-cleaning ability. Such superhydrophobic coating also exhibited a high corrosion protection efficiency of circa 99.8 % and excellent anti-icing performance, and was demonstrated to own ISO grade 1 adhesion and good chemical stability to bear 90 days of immersion in a 3.5 wt% NaCl solution and 20 days of salt spray testing without corrosion. In addition, the superhydrophobic composite coating exhibited great robustness against water impact and sand impact. Therefore, this diatomite/epoxy resin-based superhydrophobic coating can be effectively used for Mg alloy anti-corrosion and has the potential in large-scale production for practical applications.

Robust Self-Healing Graphene Oxide-Based Superhydrophobic Coatings for Efficient Corrosion Protection of Magnesium Alloys

A self-healing coating possesses a broad application prospect in the metal corrosion protection area due to its pleasurable performance. By far, despite a great deal of research studies that have been reported in this field, it is still a challenge to construct an intrinsic self-healing surface that can repair a damaged structure and restore superhydrophobicity simultaneously. Herein, a self-healing superhydrophobic coating was fabricated by combining polydopamine (PDA)-functionalized Cu2+-doped graphene oxide (GO), octadecylamine (ODA), and polydimethylsiloxane (PDMS), which can recover the superhydrophobicity and microstructure of the coating after chemical/physical damage. The as-prepared self-healing coating displayed excellent liquid repellency with a water contact angle of 158.2 ± 2° and a sliding angle of 4 ± 1°, which endowed the Mg alloy with excellent anticorrosion performance. Once the coating is scratched, the local damaged structure will be automatically repaired through the chelation of catechol and Cu2+. Also, the superhydrophobicity of the coating can be rapidly restored under 1-sun irradiation even after being etched by O2 plasma. Furthermore, the as-fabricated self-healing coating still exhibited excellent corrosion protection against a magnesium alloy after immersion in 3.5 wt % NaCl solution for 30 days, which was attributed to the efficient repair of defects in GO by PDA through π-π interactions and the inherent chemical inertia of PDMS. Moreover, the as-fabricated self-healing coating also exhibited favorable mechanical stability, chemical durability, and weather resistance. This study paves a fresh insight into the design of robust self-healing coatings with huge application potential.

Polyphthalocyanine coatings for corrosion protection on additive manufactured steel materials

Polyphthalocyanine polymer films are deposited on additive manufactured (AM) 316L steel samples for corrosion protection. Coatings were deposited on the metallic surface using a drop casting method and then set via thermal polymerization of tetracyanobenzene to produce polyphthalocyanine. The formation of the polymer film on the metal surface was confirmed by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The coated AM steel had a more positive corrosion potential compared to the uncoated sample indicating improved corrosion protection. XPS studies probed the bonding properties between the coating and additive manufactured metal surface. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) studies confirm the corrosion protection ability of the polyphthalocyanine films on AM samples in 3.5 wt% NaCl medium.

Influence of the Laser Deposited 316L Single Layers on Corrosion in Physiological Media

A multilayer laser-deposited lining of AISI 316L stainless steel makes a regular structural steel surface corrosion resistant in physiological media. Despite the application of single-layer stainless-steel linings being economically beneficial and allowing thinner surface modifications, dilution effects that modify the pitting resistance of the coating must be accounted for. In order to study the feasibility of employing single-layer coatings instead of multilayer coatings for corrosion protection in physiological media, a polarization testing back-to-back comparison was performed between laser-deposited AISI 316L monolayers on 42CrMo4 quenched and tempered steel and cold-rolled AISI 316L sheet in Dulbecco’s Phosphate Buffer Solution at 36 °C. A higher dispersion in pitting resistance, ranging from 800 mV to 1200 mV, was found on the coated samples, whereas the cold-rolled material was more stable in the 1200 mV range. The resulting differences in corrosion rates and pitting potentials open the discussion on whether the chemical composition deviations on AISI 316L dilution layers are acceptable in terms of surface functionality in medical devices.

Designing attapulgite-based self-healing superhydrophobic coatings for efficient corrosion protection of magnesium alloys

Magnesium (Mg) and its alloys are susceptible to corrosion, which affects their large-scale applications. The traditional superhydrophobic coatings for corrosion protection of Mg substrates are particularly fragile and easily damaged after prolonged exposure to harsh conditions. Herein, a superhydrophobic ODA/PDA/APT-Ce3+ (OPA-Ce3+) coating with corrosion inhibition and self-healing properties was proposed to prevent corrosion of Mg alloy via combining the cerium nitrate loaded attapulgite (APT), polydopamine (PDA) and octadecylamine (ODA). Once the OPA-Ce3+ coating was corroded, the Ce3+ adsorbed by the APT were released to form insoluble cerium oxide and hydroxides, thereby inhibiting the penetration of the corrosive substance and preventing further occurrence of corrosion. Furthermore, the OPA-Ce3+ coating exhibited favorable self-healing ability against chemical damage, which could recover its superhydrophobicity under solar exposure after O2 plasma etching. The impedance modulus (|Z|0.01 Hz) of OPA-Ce3+ coating was about 3 orders of magnitude higher than that of Mg substrate after being exposed to 3.5 wt% NaCl solution for 15 days, showing outstanding long-lasting anticorrosion performance. Moreover, the abrasion resistance and chemical stability of the as-fabricated coating were also excellent. This work is expected to provide a new perspective for preparing cost-effective and durable anticorrosion coating on metal substrates.

Electrochemical Characterization of Polymeric Coatings for Corrosion Protection: A Review of Advances and Perspectives.

The development of anti-corrosion polymeric coatings has grown exponentially in the fields of material science, chemistry, engineering, and nanotechnology during the last century and has prompted the evolution of efficient characterization techniques. Nowadays, polymeric coatings represent a well-established protection system that provides a barrier between a metallic substrate and the environment. However, the increase in complexity and functionality of these coatings requires high-precision techniques capable of predicting failures and providing smart protection. This review summarizes the state of the art for the main electrochemical techniques, emphasizing devices that track the anti-corrosion properties of polymeric coatings from the macroscale to the nanoscale. An overview of the advances in accelerated corrosion testing and the electrochemical characterization of coatings is explored, including insights into their advantages and limitations. In addition, the challenges and potential applications of the theoretical approaches are summarized based on current knowledge. Finally, this work provides the reader with the trends and challenges of designing future technologies and models capable of tracking corrosion and predicting failures.

Potentiodynamic synthesis of poly(N-vinyl carbazole) films on stainless steel to enhance corrosion resistance in sulfuric acid solution

ABSTRACT This study concerns the use of potentiodynamically synthesized poly(N-vinyl carbazole) films (PNVnCz) for corrosion protection of stainless steel (SS). The PNVnCz films were synthesized on SS by cyclic voltammetry from nonaqueous acetonitrile solution of tetrabutylammonium perchlorate and N-vinyl carbazole. The resulting PNVnCz films were characterized by ATR-FTIR and SEM. The ability of PNVnCz films to serve as corrosion protective coatings was evaluated using Eocp-time curves, potentiodynamic polarization, and EIS techniques in 1 M H2SO4 solution. Corrosion test results revealed that PNVnCz films provide anodic protection and reduce corrosion rate of SS six times at the end of 5 days’ immersion.