Smart Corrosion Research Articles

Corrosion Assessment in Reinforced Concrete Structures by Means of Embedded Sensors and Multivariate Analysis—Part 2: Implementation

The economic cost of repairing corrosion-affected reinforced concrete structures (RCSs) means that reliable and accurate assessment and early detection methods must be sought after. Conventional techniques, such as visual inspections, or measuring either cover layer resistivity or the corrosion potential, are methods that require accessibility and involve personnel having to travel to take in situ measurements. Monitoring by embedded sensors is a much more efficient approach that allows early detection by remote sensing. This work presents the implementation of a new measurement protocol regarding the existing monitoring system called INESSCOM (Integrated Sensor Network for Smart Corrosion Monitoring). Along with the corrosion intensity measurement in embedded sensors, it also proposes monitoring the double layer capacity of the sensors’ responses. It aims to determine, along with the rebars’ corrosion rate, the triggering agent of the corrosion process. This study was carried out using three reinforced concrete scaled columns that were exposed to different environments. The results demonstrate with this new protocol that the remote INESSCOM monitoring system can establish the corrosion rate and identify the precursor agent of corrosion (carbonation or chlorides), even when the recorded corrosion rates are similar.

Designing a smart polyurethane anti-corrosion coating loaded with APTES/IMZ modified halloysite nanotubes

Protective coatings are efficient for preventing corrosion, but they may not be sufficient for applications in aggressive and extreme environments, such as in coastal areas that could be subjected to corrosion. Inhibitors can suppress the corrosion rate significantly, but direct addition to the coating is ineffective because the inhibitor is easily soluble in water and can reduce the effectiveness of the barrier properties of the coating. Encapsulating the inhibitor into a nanocontainer is a promising alternative that may lead to a self-healing coating technology. Halloysite nanotubes (HNT) have been successfully reported for their application in smart coatings, and they exhibit superior aerodynamic and hydrodynamic properties and better process ability than spherical capsules for the same amount of load. Therefore, nanotubes are appropriate candidates to be used as nanocontainers for inhibitors over smart coating applications. This research discusses the design of a polyurethane coating loaded with modified halloysite nanotubes for corrosion protection of steel. Halloysite nanotubes were first functionalized using aminopropyltriethoxysilane (APTES) to improve their dispersion in the polyurethane matrix. The modified halloysite nanotubes were then loaded with the corrosion inhibitor 2-mercaptobenzimidazole (IMZ). The loaded nanotubes were incorporated into polyurethane coatings. Various characterization techniques were used to confirm the successful modification and loading of the halloysite nanotubes. The distribution of particles in the matrix was investigated by Transmission Electron Microscopy (TEM) test. The modified nanotubes showed better dispersion in the polyurethane coating, which improved the coating's barrier properties and corrosion resistance. Electrochemical Impedance Spectroscopy (EIS) and salt spray tests showed that the polyurethane coating containing the loaded and modified halloysite nanotubes exhibited the highest resistance to corrosion. The adhesion strength of the coating was also improved after immersion in a saline solution, particularly for the coating with modified and loaded halloysite nanotubes. In summary, the functionalization and loading of halloysite nanotubes improved their dispersion in the polyurethane coating, which in turn enhanced the coating's barrier properties, corrosion resistance, and adhesion strength, making it a promising approach for designing smart corrosion protective coatings.

Investigating the Synergistic Corrosion Protection Effect of an Alloy Element and Corrosion Inhibitor on Steel Reinforcement Using Machine Learning and Electrochemical Impedance Spectroscopy

Steel reinforcement in marine concrete structures is vulnerable to chloride-induced corrosion, which compromises its structural integrity and durability. This study explores the combined effect of the alloying element Cr and the smart corrosion inhibitor LDH-NO2 on enhancing the corrosion resistance of steel reinforcement. Employing a machine learning approach with a support vector machine (SVM) algorithm, a predictive model was developed to estimate the polarization resistance of steel, considering Cr content, LDH-NO2 dosage, environmental pH, and chloride concentration. The model was rigorously trained and validated, demonstrating high accuracy, with a correlation coefficient exceeding 0.85. The findings reveal that the addition of Cr and application of LDH-NO2 synergistically improve corrosion resistance, with the model providing actionable insights for selecting effective corrosion protection methods in diverse concrete environments.

Construction of BTA-inbuilt ZIF-8 coated with molybdate-intercalated ZnAl-LDH as core-shell structured nanocontainers toward pH-responsive smart corrosion protection of waterborne epoxy coating

Nanocontainers encapsulating corrosion inhibitors are commonly incorporated into organic coatings to enable self-healing effects, thereby ensuring long-term anticorrosion performance. In this study, a novel dual corrosion inhibitor-loaded self-healing nanocontainer with core-shell structure was proposed for fabricating composite waterborne epoxy coatings with both active and passive corrosion prevention properties.The nanocontainer, named BTA-ZIF-8@LDH-Mo, was synthesized through the in-situ growth of molybdate-intercalated ZnAl layered double hydroxide (LDH-Mo) on the surface of 1H-benzotriazole-inbuilt zeolitic imidazolate framework (BTA-ZIF-8). Potentiodynamic polarization results showed that the Icorr of bare Q235 carbon steel immersed in a 3.5 wt% NaCl solution decreased from 4.658 × 10−6 A/cm2 to 1.274 × 10−6 A/cm2 after introducing BTA-ZIF-8@LDH-Mo nanocontainers, resulting in a superior corrosion inhibition efficiency of 72.65 %. Electrochemical impedance spectroscopy further demonstrated that the |Z|f=0.01Hz of epoxy coating doped with BTA-ZIF-8@LDH-Mo reached 4.24 × 109 Ω·cm2 after 42 d of immersion in 3.5 wt% NaCl solution, approximately 30 times higher than that of pure EP coating. Moreover, investigations on artificially scratched coatings indicated that the incorporation of BTA-ZIF-8@LDH-Mo nanocontainers effectively mitigated the corrosion process by forming an inhibiting layer on the metal substrate that impeded the corrosion process. The dual corrosion inhibitor strategy relies on the synergistic action of BTA pre-loaded in ZIF-8 nanoparticles and molybdate (MoO42-) intercalated in LDH interlayers for active corrosion protection. Additionally, the nanocontainers enhance passive protection by elongating the diffusion paths of corrosive media and trapping chloride ions. This nanocontainer design offers a facile strategy for fabricating a smart coating with the excellent anticorrosion properties.

Emerging Mo-doped MgAl-LDH lamellar/carbon nanotubes as 3D sustainable nanohybrid for designing a durable smart anti-corrosion composite

This paper focused on the utilization of 3D hybrid nanocomposites composed of layered double hydroxides (L) containing sodium molybdate (SM), which are chemically bonded with functionalized multi-walled carbon nanotubes (FCN), as nanocarriers for smart corrosion prevention. The SM molecules were loaded into the L, and L/FCN nanocarriers by an anion exchange process, and then the 3 synthesized nanoparticles (L, SM-L, and SM-L/FCN) were characterized. Based on the electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PD) tests' outcomes, the maximum corrosion prevention efficiency (about 90.88 %) belongs to the SM-L/FCN nano reservoir containing saline extract. Additionally, for the epoxy phase, the EIS results (on the intact and scratched specimens) revealed a significant diminish in the chloride and water penetration into the epoxy coating during 63 days of immersion for intact and 24 h for scratched states. EIS results indicated the enhancement of the charge transfer resistance (Rct) of the scratched coatings, from 17.42 kΩ.cm2 for the EP sample to 72.47 kΩ.cm2 for the SM-L/FCN/EP one in long immersion times, revealing the self-repairing behavior of the designed coating. The results of intact coating revealed that the Log (|Z|0.01 Hz) value reached 10.63 in long immersion time indicating a decreased occurrence of coating disbondment attributed to the electrolyte infiltration and corrosion of the underlying metal substratum. According to the pull-off and cathodic disbonding tests results, there was an enhancement in adhesion (51.5 % decrease in loss of adhesion strength, & a 52 % decline in diameter of cathodic disbondment), and a strong interaction between the interface of epoxy and substratum. According to the mechanical tests (tensile and DMTA) results the incorporation of L and FCN nanoparticles into the SM-L/FCN sample enhanced the nanocomposite's mechanical properties. The tensile test showed an increase in ultimate tensile strength (σUTS) and elongation at break (Ɛb) of 130.61 % and 107.59 %, respectively, compared to the pure epoxy (EP) sample. Additionally, the dynamic mechanical thermal analysis (DMTA) test indicated a 144 % increase in crosslinking density for the SM L/FCN sample compared to the neat epoxy.

High-Loading Smart Carrier Containing 2-Mercaptobenzimidazole-Zn2+-Polydopamine with pH-Responsive Function to Fabricate High-Performance Waterborne Epoxy Anticorrosion Coatings.

Corrosion inhibitor additives are considered to be one of the effective methods to slow down the corrosion of metals, but the corrosion inhibitors will decompose and lose their effect in a long-term corrosive environment. In this work, a smart corrosion inhibitor carrier 2-mercaptobenzimidazole-Zn2+-polydopamine@graphite (MZPG) with excellent pH response was designed and synthesized using a one-pot method. This corrosion inhibitor carrier not only has a very high 2-mercaptobenzimidazole (MBI) loading capacity (38.0%) but also maintains a very low MBI activity to inhibit the decomposition of MZPG in the environment as much as possible. The MZPG/epoxy (MZPG/EP) coatings prepared by the spraying method showed excellent mechanical properties. Electrochemical and salt spray tests showed that the MZPG/EP coatings (1.20 × 1010 Ω·cm2) have excellent corrosion resistance with Rp values up to 3 orders of magnitude higher than that of the EP coating (1.25 × 107 Ω·cm2). Notably, the MZPG/EP coatings maintained good corrosion resistance under acidic conditions due to the pH-responsive release of corrosion inhibitors. This is of great significance for the future development of coatings for highly corrosive environments.

PH‐Responsive Chitosan Microspheres Loaded with Gemini Imidazolium‐Based Ionic Liquids as Smart Corrosion Inhibitors for N80 Steel in Hydrochloric Acid Solution

Chitosan microspheres (CSM) loaded with synthesized Gemini imidazolium‐based ionic liquids ([C2(Bim)2]Cl2@CSM and [C6(Bim)2]Br2@CSM) are constructed as smart corrosion inhibitors to protect N80 steel in hydrochloric acid solution. The optimal inhibition efficiency of [C2(Bim)2]Cl2 and [C6(Bim)2]Br2 at 300 mg L−1 reaches 94.68% and 95.96%, respectively, indicating mixed‐type inhibition behavior. On this basis, the prepared [C2(Bim)2]Cl2@CSM and [C6(Bim)2]Br2@CSM can proactively identify corrosive environments and protect the metal. The microspheres are pH‐responsive owing to the presence of Schiff‐base C═N bonds and the loaded inhibitors can be released rapidly in acidic environment. Released inhibitors are delivered to corroded sites and synergistically interact with decomposed microspheres for enhanced corrosion inhibition effect.

Corrosion protection of steel bar enabled by monofluorophosphate-bearing composites with sustained-release capability

This paper selected the polyethylene (PE) and polystyrene (PS) as polymer carriers of the sodium monofluorophosphate (MFP) to prepare PE/MFP and PS/MFP composites using melt-extrusion technique with a sustained-release capacity for smart corrosion protection. The releasing behavior of two MFP-containing composites in the simulated concrete pore solution was evaluated in terms of residual content, releasing rate and the side/fractured surface micro-morphologies. Besides, related releasing mechanisms of MFP-bearing polymer composites are explained, which are different from the mechanisms of most microcapsules and tablets. The experimental analyses showed that two composites all displayed a uniform elemental distribution on their side surface and intrinsic hydrophobicity. The PE/MFP composites obtained higher initial encapsulation efficiency and a lower but relatively controllable releasing rate compared to the PS/MFP composites due probably to the higher hydrophobicity and crystallinity of the PE carrier. In addition, the physical appearance of the corroded carbon steel bar after immersion in sodium chloride-contaminated simulated concrete pore solutions and corresponding electrochemical outcomes revealed that PE/MFP composites generally led to better corrosion protection performance than the PS/MFP counterpart, which could be due to their better sustained-release capacity. The obtained composites provide another promising option as concrete inhibitors, making inroads into improving the long-term durability of concrete structures.

Corrosion Assessment in Reinforced Concrete Structures by Means of Embedded Sensors and Multivariate Analysis-Part 1: Laboratory Validation.

Reinforced Concrete Structures (RCS) are a fundamental part of a country's civil infrastructure. However, RCSs are often affected by rebar corrosion, which poses a major problem because it reduces their service life. The traditionally used inspection and management methods applied to RCSs are poorly operative. Structural Health Monitoring and Management (SHMM) by means of embedded sensors to analyse corrosion in RCSs is an emerging alternative, but one that still involves different challenges. Examples of SHMM include INESSCOM (Integrated Sensor Network for Smart Corrosion Monitoring), a tool that has already been implemented in different real-life cases. Nevertheless, work continues to upgrade it. To do so, the authors of this work consider implementing a new measurement procedure to identify the triggering agent of the corrosion process by analysing the double-layer capacitance of the sensors' responses. This study was carried out on reinforced concrete specimens exposed for 18 months to different atmospheres. The results demonstrate the proposed measurement protocol and the multivariate analysis can differentiate the factor that triggers corrosion (chlorides or carbonation), even when the corrosion kinetics are similar. Data were validated by principal component analysis (PCA) and by the visual inspection of samples and rebars at the end of the study.

Cloud-based pipe corrosion monitoring using electromechanical impedance instrumented piezoelectric ring sensor

The corrosion of small-diameter pipes has resulted in numerous significant accidents and substantial economic losses in both industrial and civil sectors. This paper presents a wireless smart corrosion monitoring system based on electromechanical impedance (EMI) technology. This system comprises a smart corrosion sensing node (SCSN) designed using EMI principles and a wireless impedance monitoring system (WIMS) for remote impedance measurement. A finite element simulation was conducted to assess the performance of the SCSN under uniform corrosion conditions. Additionally, a comparative test, with and without fluid inside the pipe, was performed to determine the impact of the fluid on test results. To validate the effectiveness of the proposed wireless smart corrosion monitoring node, corrosion monitoring experiments were conducted on pipe specimens equipped with the sensing node. These findings were complemented by separate corrosion experiments, and it was revealed that as corrosion increased, the peak frequency decreased, indicating a strong linear relationship. The study demonstrates that the wireless smart corrosion monitoring node is highly capable of monitoring pipe corrosion in an experimental setting.

On the Development of an Intelligent Poly(aniline-co-o-toluidine)/Fe3O4/Alkyd Coating for Corrosion Protection in Carbon Steel

The corrosion of metals and alloys presents a significant challenge in many industries, demanding constant maintenance, and thereby increasing costs. In response to this problem, the smart corrosion protection coating has emerged as a promising solution. By enabling the immediate detection of, and response to, environmental changes, such as in the temperature and pH, these smart coatings contribute significantly to extending a material’s lifespan, and reducing maintenance expenses. In this study, nanomagnetic [poly(aniline-co-o-toluidine)/Fe3O4] systems were prepared and used as a self-healing corrosion inhibitor, mixed with alkyd paint at different weight percentages (5–25%). The composites were used as a coating on carbon steel (C1010), and their corrosion protection performance was tested in 0.1 mol/L HCl, using electrochemical impedance spectroscopy (EIS), scanning electron microscope (SEM), and FTIR analyses. The results showed an adequate corrosion inhibition performance for the developed composites, compared to the alkyd paint alone, reaching an inhibition efficiency of 80% at 20 wt.% of composite. Adding increasing weight percentages of the developed composites to the paints led to a significant increase in the corrosion resistance, accompanied by a remarkable decrease in the double-layer capacitance. Thus, these developed composites show excellent potential as a corrosion protection formulation in paints.

A Waterborne Epoxy Composite Coating with Smart Corrosion Resistance Based on 2-Phenylbenzimidazole-5-sulfonic Acid/Layered Double Hydroxide Composite

In this study, ZnAl-layered double hydroxide (ZnAl-LDH) was functionalized with 2-Phenylbenzimidazole-5-sulfonic acid (PBSA) to prepare ZnAl-PBSA-LDH using a simple one-step method. The electrochemical impedance spectroscopy (EIS) result of the solution phase demonstrated excellent corrosion inhibition performance of ZnAl-PBSA-LDH. Subsequently, 0.6 wt.% ZnAl-PBSA-LDH with shielding effects and active inhibition was incorporated into the water-based epoxy (WEP) for preparing the high-performance anti-corrosion coating (6-ZPL/WEP). The EIS test illustrated that the 6-ZPL/WEP coating maintained a high low-frequency impedance modulus (|Z0.01 Hz|) after 30 days of immersion, which is nearly two orders of magnitude higher compared to that of the blank coating. These results demonstrated that ZnAl-PBSA-LDH could efficiently improve the corrosion resistance of the WEP coating. Therefore, this study introduces new insights into the use of layered double hydroxides (LDHs) in the domain of anti-corrosion.

Hierarchically self-reporting and self-healing photothermal responsive coatings towards smart corrosion protection

For conventional anticorrosion coatings, it is challenging to simultaneously report and repair two failure stages involving coating damage and interfacial metal corrosion. Thus, it leads to difficulties for continuous detection of coating service status, and may result in premature failure of metal-based equipment. Herein, we present a novel photothermal responsive composite epoxy system with hierarchical damage reporting and healing capabilities, which is enabled by mesoporous polydopamine nano-spheres loaded with crystal violet lactone (CVL) and phenanthroline (Phen). In our design, the coating damage is indicated by the immediately intensified fluorescent and can be rapidly closed in 90 s of NIR irradiation. Furthermore, the on-demand released corrosion probes (Phen) are able to chelate with Fe2+ ions generated from localized corrosion, producing distinct visual red color to report corrosion pits and resisting corrosion developing process. The proposed smart coatings provide a concept for achieving hierarchically self-reporting and self-repairing function of general coating defects and substrate corrosion, thus having certain potential to be applied in smart anticorrosion applications.

A novel smart coating with hexacyanoferrate intercalated layered double hydroxides nanoadditive for early detection of carbon steel corrosion

The detection of corrosion at early stages could increase the service life of metal-based infrastructures in a cost-effective manner. Despite the recent progress in “smart” self-reporting corrosion sensing coatings, the development of environmentally friendly systems appropriate for steel substrate used in offshore applications remains a relevant challenge. In this study, a novel smart corrosion sensing coating, based on hexacyanoferrate intercalated Mg-Al LDH nanoadditive, was developed, aiming at the detection of early-stage corrosion of carbon steel. The detection mechanism is based on the ability of hexacyanoferrate ions to react with iron cations generated during the corrosion process, giving rise to a colorimetric signal, while LDH carriers provide a controlled release of active ions under corrosion conditions. The sensing nanoadditive was embedded into a commercial pigment-free water-based acrylic polyurethane coating. The nanomaterial was characterized structurally (XRD) and morphologically (STEM). The compatibility of the additive with the polymer formulation and its influence on the resulting coating performance was investigated in terms of rheological behavior, structure (FTIR), morphology (SEM/EDS), thermal (TGA, DSC) and mechanical (adhesion, hardness) properties. The corrosion protection ability of the coating was evaluated via EIS, while the sensing functionality was analyzed by visual analysis of the surface. The developed coating successfully detects early-stage corrosion of steel substrate at a lab scale, in conditions relevant to the use of metallic structures in offshore applications, demonstrating a correlation between the level of material degradation and the spectroscopic signal associated with the presence of the LDH functional nanoadditive. Furthermore, the observed decrease in coating barrier properties, caused by the presence of LDH, was overcome by the subsequent development of a multilayer coating system. Two different topcoats (epoxy- and polyurethane-based) were surveyed for this purpose, showing an improvement in the coating barrier properties without influencing the corrosion detection functionality of the sensing layer. The results were successfully validated by standard salt spray tests. The multilayer approach opens up the possibility to model coatings with different characteristics for various operating conditions.

Reliability Improvement of Magnetic Corrosion Monitor for Long-Term Applications.

Electromagnetic techniques are widely employed for corrosion detection, and their performance for inspection of corrosion is well established. However, limited work is carried out on the development and reliability of smart corrosion monitoring devices for tracking internal or buried thickness loss due to corrosion remotely. A novel smart magnetic corrosion transducer is developed for long-term monitoring of thickness loss due to corrosion at critical locations. The reliability of the transducer is enhanced by using a dissimilar active redundancy approach. The improved corrosion monitor has been tested in the ambient environment for seven months to evaluate the stability against environmental factors and degradation. The monitor is found to show great sensitivity to detect defects due to corrosion. Detection of anomalous patterns in the time series data received from the monitors is accomplished by using Pearson's correlation coefficient. The critical component of the monitor is identified at the end of the test. Research findings reveal that, compared to the existing corrosion monitoring techniques in the industry, the detection and isolation of faulty sensor features introduced in this study can contribute to reliable monitoring of thickness loss due to corrosion in ferromagnetic structures over an extended period of time.

An effective and smart corrosion inhibitor in acidic environment: Experimental & theoretical studies

An effective and smart corrosion inhibitor in acidic environment: Experimental & theoretical studies

Visible light-triggered smart photoreversible color switching systems based on VOx QDs for constructing smart corrosion resistant coatings on AA2024-T3

Nanoparticles rich in oxygen vacancies (such as ZnO1-x, SnO2-x, TiO2-x, CeO2-x) are major components of Photoreversible color-switching systems (PCSSs) and are utilized in many applications (ink-free paper printing, secure communication and smart fabrics). Despite this, it has been a challenge to develop smart coatings due to several factors (such as low durability and poor efficiency in charge separation). To solve these issues, we have synthesized oxygen deficient vanadium oxide (VOx) quantum dots with a size of ∼ 2 nm through solvothermal reaction by using l-ascorbic acid as a reducing agent, resulting in widened photoabsorption spectrum with a band gap of 2.15 eV. Oxygen deficient VOx, methylene blue and acrylic latex (VOx/MB/Ac2403) have been used to design PCSSs coating on AA2024-T3 metal alloy. The redox dyes can be photocatalytically reduced by visible laser light, resulting in remote printing of various designs on the smart coating in ∼ 120 s. When irradiated with blue light, the designs can be erased in ∼ 250 s caused by the VOx self-catalyzed oxidation, leading to high recyclability (more than 40 cycles), efficiency and durability. As a result, reprintable smart coatings offer a viable alternative to regular alloys in meeting the growing demands for security or camouflage.

Sodium lignosulfonate-loaded ZnAl-layered double hydroxide decorated graphene oxide nanolayers; toward fabrication of sustainable nanocomposite for smart corrosion prevention

In this study, the NO3− intercalated ZnAl-based layered double hydroxide (LDH) nanostructures decorated graphene oxide (GO) nanosheets were synthesized, loaded with sodium lignosulfonate (SLS), and finally modified with aminopropyltriethoxysilane (APS) to reach a high-performance corrosion inhibitor nanocarriers. The morphology and chemistry of the LDH-rGO nanostructures were evaluated by the FE-SEM, EDX, FT-IR, XPS, XRD, Raman, and TGA techniques. Characterization results of SLS@LDH-rGO nanostructures proved the uniform decoration of GO nanosheets with LDH nanolayers and the loading of the SLS inhibitor. The active/barrier corrosion mitigation ability (CMA) of the synthesized nanostructures was studied by EIS and potentiodynamic polarization (PP) tests in both solution (NaCl) and coating (epoxy) phases. Results showed the increment of the total resistance and decrement of the current density of MSSs immersed in the SLS@LDH-rGO extract by 358 and 79%, respectively, compared to the blank solution after 48 h. EIS results proved the bi-functional active-inhibitive/barrier CMA for the SLS@APS-LDH-rGO filled epoxy coatings. The total impedance of the intact SLS@APS-LDH-rGO filled epoxy coating was enhanced by about 9700% after 8 weeks compared to that of the blank coating.

Nano-sized cerium vanadium oxide as corrosion inhibitor: A microstructural and release study

• A simple chemical route to synthesize cerium vanadate. • Mixed nanostructure. • Cerium vanadate is an effective corrosion inhibitor for ferrous alloys. • It forms a layer on the steel surface. • Self-healing and smart corrosion inhibitor. The synthesized, nano-sized cerium vanadate is proposed as a self-healing corrosion inhibitor for ferrous alloys (e.g., automotive high strength steel (HSS) and mild steel (MS)). Cerium vanadate prepared at two different pH conditions (neutral and basic) showed similar corn-like morphology with nanorod structure. UV-Vis spectroscopy studies revealed that the release rate of cerium vanadate-B (basic condition) was higher than cerium vanadate-N (neutral condition) in 0.1 M NaCl solution. The specimen exposed to 0.1 M NaCl containing a supersaturated solution of cerium vanadate-B (1000 ppm) revealed 8 times and 6 times lower corrosion current density values for HSS and MS respectively than that of the one without corrosion inhibitor. There was a gradual increase in the film resistance ( R film ) on both HSS and MS observed as a function of exposure time in corrosive medium containing cerium vanadate-B inhibitor. An order higher impedance values were observed for both HSS and MS immersed for 168 h, highlighting the self-healing effect of the cerium vanadate compound. The X-ray photoelectron spectroscopy results showed the presence of multivalent oxidation states of both cerium and vanadium species. The inhibiting action is attributed to the high solubility of cerium vanadate in the corrosive medium to form a film on the metal surface. The dissolution/solubility of the corrosion inhibitor was more favorable in neutral to alkaline conditions than in acidic conditions.

Smart Anticorrosion Coatings Based on Poly(phenylene methylene): An Assessment of the Intrinsic Self-Healing Behavior of the Copolymer.

Poly(phenylene methylene) (PPM) is a multifunctional polymer featuring hydrophobicity, high thermal stability, fluorescence and thermoplastic processability. Accordingly, smart corrosion resistant PPM-based coatings (blend and copolymer) were prepared and applied by hot pressing on aluminum alloy AA2024. The corrosion protection properties of the coatings and their dependence on coating thickness were evaluated for both strategies employed. The accelerated cyclic electrochemical technique (ACET), based on a combination of electrochemical impedance spectroscopy (EIS), cathodic polarizations and relaxation steps, was used as the main investigating technique. At the coating thickness of about 50 µm, both blend and copolymer PPM showed effective corrosion protection, as reflected by |Z|0.01Hz of about 108 Ω cm2 over all the ACET cycles. In contrast, when the coating thickness was reduced to 30 µm, PPM copolymer showed neatly better corrosion resistance than blended PPM, maintaining |Z|0.01Hz above 108 Ω cm2 with respect to values below 106 Ω cm2 of the latter. Furthermore, the analysis of many electrochemical key features, in combination with the optical investigation of the coating surface under 254 nm UV light, confirms the intrinsic self-healing ability of the coatings made by PPM copolymer, contrary to the reference specimen (i.e., blend PPM).