Facile and eco-friendly synthesis of polyaniline/ZnO composites for corrosion protection of AA-2024 aluminium alloy

Investigation of the Release Rate of Biocide and Corrosion Resistance of Vinyl-, Acrylic-, and Epoxy-Based Antifouling Paints on Steel in Marine Infrastructures

This study comprehensively assesses the release rate of biocides, corrosion effects related to antifouling, and the physical properties of different paint types. Tests were conducted to measure thickness, viscosity, hardness, bending, adhesion, gloss, impact resistance, abrasion resistance, scratch resistance, polarization, and salt spray. The paints evaluated include resin-based, acrylic-based, epoxy-based, and vinyl-based formulations. The study investigates the influence of biocide content, biocide particle size, and immersion time on release rate using a lab-scale setup. Results showed that acrylic-based paints had a higher biocide release rate due to faster hydrolysis, while smaller biocide particle sizes led to higher release rates in resin-based paints. Optimal total biocide contents were determined to be 30% for acrylic-based, 60% for epoxy-based, and 50% for vinyl-based paints. Antifouling corrosion analysis demonstrated that sample with an optimal release rate effectively prevent algae growth and fouling. Acrylic-based paint with 30 wt.% biocide content exhibited superior adhesion with a dolly separation force of 4.12 MPa. Evaluating the impact of synthesized polyaniline on 30 wt.% epoxy-based paint, a sample coated with 10 wt.% polyaniline represented a low corrosion rate of 0.35 µm/year and a high impedance value of approximately 37,000 Ohm·cm-2.

Silk Fibroin/ZnO Coated TiO2 Nanotubes for Improved Antimicrobial Effect of Ti Dental Implants

The aim of the present research is to develop a novel hybrid coating for a Ti dental implant that combines nature-inspired biomimetic polymers and TiO2 nanostructures with an entrapped ZnO antimicrobial agent. ZnO was used in other studies to cover the surface of Ti or Ti-Zr to reduce the need of clinical antibiotics, prevent the onset of peri-implantitis, and increase the success rate of oral clinical implantation. We developed an original coating that represents a promising approach in clinical dentistry. The titanium surface was first anodized to obtain TiO2 nanotubes (NT). Subsequently, on the NT surface, silk fibroin isolated from Bombyx mori cocoons was deposited as nanofibers using the electrospun technique. For an improved antibacterial effect, ZnO nanoparticles were incorporated in this biopolymer using three different methods. The surface properties of the newly created coatings were assessed to establish how they are influenced by the most important features: morphology, wettability, topography. The evaluation of stability by electrochemical methods in simulated physiological solutions was discussed more in detail, considering that it could bring necessary information related to the behavior of the implant material. All samples had improved roughness and hydrophilicity, as well as corrosion stability (with protection efficiency over 80%). The antibacterial test shows that the functional hybrid coating has good antibacterial activity because it can inhibit the proliferation of Staphylococcus aureus up to 53% and Enterococcus faecalis up to 55%. All Ti samples with the modified surface have proven superior properties compared with unmodified TiNT, which proved that they have the potential to be used as implant material in dentistry.

In Situ Electrochemical Monitoring of the Crevice Corrosion Process of the 7075-T651 Aluminium Alloy in Acidic NaCl and NaNO3 Solution

The crevice corrosion of the 7075-T651 aluminium alloy was investigated using in situ electrochemical impedance spectroscopy (EIS), potentiodynamic polarization curves (PC), and H⁺ sensors in acidic NaCl solution with different contents of NaNO₃. In the solution without NaNO₃, the pH in the crevice increased rapidly and gradually reached a relatively stable status. The corrosion of the aluminium alloy in the crevice was inhibited and crevice corrosion could not be initiated. In the solution with NaNO₃, the pH increased rapidly at the initial immersion period and then decreased gradually. The corrosion of the aluminium alloy inside the crevice could be enhanced and the corrosion of the aluminium alloy outside crevice could be inhibited. This triggered crevice corrosion in the solution with NaNO₃. The inhibited corrosion outside the crevice can be attributed to the improved passive film of the specimen outside the crevice by nitrate. The accumulated secondary products of ammonia inside the crevice led to selective dissolution of copper, which triggered the nucleation of pitting corrosion and promoted the corrosion of the specimen inside the crevice.

Broad-class volatile organic compounds (VOCs) detection via polyaniline/zinc oxide (PANI/ZnO) composite materials as gas sensor application

Metal-oxide doped conductive polymers have been investigated as sensors in the field of gas-sensing. Recent developments have highlighted the role of intrinsically conductive polymers, that have reportedly offered high surface response towards the detection of volatile organic compounds (VOCs). In this work, we optimize the development of gas-sensors made of Polyaniline/Zinc oxide (PANI/ZnO) composite, capable of detecting a varied class of VOCs such as, ammonia, acetone, formaldehyde, methanol, and ethanol. The conductivity of these sensors is evaluated at room temperature and are investigated until saturation. In addition to the final application, this work also focusses on the synthesis strategies to achieve an 'optimal' matrix-to-additive ratio, such that superior chemical response is paralleled with mechanical robustness for PANI based sensors. The PANI/ZnO composites are casted into sensors bearing different additive ratios, via a drop-casting method and the same is evaluated for its formability and mechanical behavior. Physio-chemical characterization was performed using Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscope (SEM), and Energy Dispersive X-ray Analysis (EDX) and we report on an exceptional selectivity for ammonia with an average sensor response of 3496.67 mV by all the sensors, when fabricated using different matrix-additive ratios. This result is superior to what is observed for Pure- PANI sensors that were selective only to methanol and ethanol. The addition of ZnO in the smallest fraction, already offers a broader range of selectivity, e.g., PANI/ZnO 90:10 sensor was selective to formaldehyde as assessed using pattern recognition.

Metals and metal oxides polymer frameworks as advanced anticorrosive materials: design, performance, and future direction

Metals (Ms) and metal oxides (MOs) possess a strong tendency to coordinate and combine with organic polymers to form respective metal–polymer frameworks (MPFs) and metal oxide polymer frameworks (MOPFs). MPFs and MOPFs can be regarded as composites of organic polymers. MPFs and MOPFs are widely used for industrial and biological applications including as anticorrosive materials in the aqueous phase as well as in the coating conditions. The presence of the Ms and MOs in the polymer coatings improves the corrosion inhibition potential of MPFs and MOPFs by improving their self-healing properties. The Ms and MOs fill the micropores and cracks through which corrosive species such as water, oxygen, and corrosive ions and salts can diffuse and destroy the coating structures. Therefore, the Ms and MOs enhance the durability as well as the effectiveness of the polymer coatings. The present review article is intended to describe the corrosion inhibition potential of some MPFs and MOPFs of some most frequently utilized transition metal elements such as Ti, Si, Zn, Ce, Ag, and Au. The mechanism of corrosion inhibition of MPFs and MOPFs is also described in the presence and absence of metal and metal oxides.

Ti3C2Tx MXene Polymer Composites for Anticorrosion: An Overview and Perspective

As the most studied two-dimensional (2D) material from the MXene family, Ti₃C₂T_x has constantly gained interest from academia and industry. Ti₃C₂T_x MXene has the highest electrical conductivity (up to 24,000 S cm^-1) and one of the highest stiffness values with a Young's modulus of ∼ 334 GPa among water-dispersible conductive 2D materials. The negative surface charge of MXene helps to disperse it well in aqueous and other polar solvents. This solubility across a wide range of solvents, excellent interface interaction, tunable surface functionality, and stability with other organic/polymeric materials combined with the layered structure of Ti₃C₂T_x MXene make it a promising material for anticorrosion coatings. While there are many reviews on Ti₃C₂T_x MXene polymer composites for catalysis, flexible electronics, and energy storage, to our knowledge, no review has been published yet on MXenes' anticorrosion applications. In this brief report, we summarize the current progress and the development of Ti₃C₂T_x polymer composites for anticorrosion. We also provide an outlook and discussion on possible ways to improve the exploitation of Ti₃C₂T_x polymer composites as anticorrosive materials. Finally, we provide a perspective beyond Ti₃C₂T_x MXene composition for the development of future anticorrosion coatings.

Rising of MXenes: Novel 2D-functionalized nanomaterials as a new milestone in corrosion science - a critical review

Corrosion is a natural process between a metal and its environment that can gradually cause catastrophic damage to the metal equipment, which would have economic implications. Consequently, several protective methods have been utilized to prevent metals from severe degradation. Organic polymeric coatings have been widely used as the most convenient and cost-effective method to boost metals' anti-corrosion properties. Nonetheless, these coatings have a significant amount of solvent, resulting in shrinkage and micro defects in the films during the curing process. Many studies have verified that transition metal carbides/nitrides (MXenes) can form a "labyrinth effect" in the polymeric coatings due to their "nano-barrier effect". Furthermore, based on their sheet-like structures, they can considerably cover the surface defects of the polymeric films. Therefore, the penetration of corrosive elements can be substantially curbed. It is the first review that specifically focused on the new family of 2D nanomaterials, i.e., MXenes, and discussed their applications in corrosion protection systems. The MXenes' pros and cons in the polymeric matrixes as nanofillers will be clarified. Moreover, the synthesis and functionalization methods of the MXenes, their applications, and corrosion protection mechanism will be explored. Subsequently, the MXenes' superiority over other 2D nanomaterials will be highlighted while their future perspectives and industrial applications will be predicted.

Synthesis and characterization of polyaniline-hydrotalcite-graphene oxide composite and application in polyurethane coating

In this paper, a composite from polyaniline and graphene oxide-hydrotalcite hybrid (PAN–HG) was fabricated by direct polymerization of aniline using ammonium persulphate as an oxidant in the presence of a HG hybrid. The structure and morphological properties of synthesized PAN–HG composites were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), Raman spectra, and scanning electron microscopy (SEM) techniques. The electrochemical properties of the composite particles were also analyzed by potentiodynamic polarization curves to evaluate the corrosion inhabitation. The results were calculated by Tafel fitting and showed that the effective corrosion protection values were 73.11%, 88.46%, and 95.49%, corresponding to HG, 1PAN–HG, and 2PAN–HG. The influence of PAN–HG on the corrosion protection of the polyurethane coating applied on the CT3 steel was investigated. As a result, the PU containing 0.5% of 2PAN–HG showed the most effective protection of the CT3 steel substrate. The R_C of the coating was about 1.61 × 10⁷ Ω cm², and after immersion for 30 days, the R_C value was 0.17 × 10⁶ Ω cm². From all the analyzed results, PAN–HG has enhanced the corrosion protection and a complicated protection mechanism was also concluded and explained.

Corrosion protection: PAN–HG performed effect of 95.49% protection of CT3-steel in NaCl 3.5%. PU(PAN–HG) coating provides good corrosion protection with complex mechanism of high barrier, ion-exchange and e⁻ trapping to HG structure.