Waterborne epoxy resin (WEP) has been widely used as an anti-corrosive coating for metals. However, it is still a big challenge to further improve its anti-corrosion performance due to the poor barrier properties to corrosive media. In this study, fluorinated graphene (FG) was used as a filler in WEP to improve its barrier properties, which contributes to corrosion resistance enhancement. The chemical composition and microstructures of FG and FG-modified WEP were systematically analyzed, and its corrosion resistance was also studied. Results reveal that the addition of FG sheet to WEP not only can significantly improve the tensile strength of WEP coating, but also increase the barrier properties of WEP coating and block the penetration of corrosive agent throughout the coating to the interface between coating and substrate. Meanwhile, the results also declare that the F content of FG has a significant effect on mechanical properties and long-term corrosion resistance, and the performance of FG-modified WEP coating will deteriorate with the increase of F content.

To enhance the various properties of polyvinyl alcohol (PVA), varying concentrations of carboxy-functionalized graphene (CFG) were employed in the preparation of CFG/PVA nanocomposite films. FTIR and XRD analyses revealed that CFG, in contrast to graphene, not only possesses carboxylic acid group but also exhibits higher crystallinity. Mechanical testing indicated a notable superiority of CFG addition over graphene, with optimal mechanical properties such as tensile and yield strengths being achieved at a 3% CFG concentration. Relative to pure PVA, the tensile strength and yield strength of the composite increased by 2.07 and 2.01 times, respectively. XRD analysis showed distinct changes in the crystalline structure of PVA with the addition of CFG, highlighting the influence of CFG on the composite structure. FTIR and XPS analyses confirmed the formation of ester bonds between CFG and PVA, enhancing the overall performance of the material. TGA results also demonstrated that the presence of CFG enhanced the thermal stability of CFG/PVA nanocomposite films. However, analyses using scanning electron microscopy and transmission electron microscopy revealed that a 3% concentration of CFG was uniformly dispersed, whereas a 6% concentration of CFG caused aggregation of the nanofiller, leading to a decrease in performance. The incorporation of CFG significantly enhanced the water vapor and oxygen barrier properties of PVA, with the best performance observed at a 3% CFG concentration. Beyond this concentration, barrier properties were diminished owing to CFG aggregation. The study further demonstrated an increase in electrical conductivity and hydrophobicity of the nanocomposites with the addition of CFG. Antibacterial tests against E. coli showed that CFG/PVA nanocomposites exhibited excellent antibacterial properties, especially at higher CFG concentrations. These findings indicate that CFG/PVA nanocomposites, with an optimized CFG concentration, have significant potential for applications requiring enhanced mechanical strength, barrier properties, and antibacterial capabilities.

Purpose: The purpose of this study is to modify cerium dioxide with fumaric acid (CeO₂-f) to improve its compatibility and dispersibility in epoxy resin and to investigate the effect of the content on the coating performance. Design/methodology/approach: To investigate whether CeO₂-f reacts with epoxy resin by ring opening, CeO₂-f and epoxy resin-treated CeO₂-f (Ce CeO₂-f/EP) were analyzed by infrared radiation (IR), X-ray diffraction (XRD) and ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis). To reveal the effect of different content on coatings properties, neutral salt spray test (NSST) and electrochemical test were performed. Findings: The results of IR, XRD, X-ray photoelectron spectroscopy and UV-Vis indicated that fumaric acid attached to the CeO₂ surface by chemical bonding and underwent a ring-opening reaction with epoxy resin, thus, improving the compatibility of CeO₂ in epoxy resin. NSST and electrochemical impedance spectroscopy results showed that the coatings containing 5% CeO₂-f exhibited the optimal corrosion resistance. The reason is that a dense conversion film was established on the substrate surface. Originality/value: The epoxy coatings using CeO₂-f as fillers with synergistic inhibition ability are promising for the protection of carbon steel.

Purpose: The purpose of this paper was to research the influence of polyaniline/montmorillonite (PANI/OMMT) composite powder content on the corrosion protection of epoxy (EP) coating. Design/methodology/approach: The polyaniline/montmorillonite/epoxy (PANI/OMMT/EP) coatings containing different contents of PANI/OMMT composite powder were prepared on steel. The corrosion protection performances of PANI/OMMT/EP coatings in 3.5 per cent NaCl solutions were investigated by electrochemical impedance spectroscopy. The barrier property of coatings was examined using water absorption analysis. The structure and crosslink density of coatings were examined using scanning electron microscopy and differential scanning calorimetry, respectively. Findings: The PANI/OMMT composite powder could enhance the barrier properties of the EP coating and reduce the corrosion rate of the steel beneath the coating. The coating showed the best corrosion protection performance when 3 per cent PANI/OMMT powder was added to the coating. Originality/value: The research clarified the influence of PANI/OMMT content on the corrosion protection of coating from two aspects: one is the barrier performance of the coating; the other is the corrosion inhibitors for metal substrate.

Herein, novel microcapsules were designed and synthesized by emulsion polymerization and used for self-healing coating for magnesium alloy . Polyaniline (PANI) was used directly as a capsule shell, and thermoplastic acrylic resin was used as the core material. Polymerization processes of microcapsules were observed by optical microscopy , and some key polymerization parameters were discussed. Composite microcapsules were analyzed by scanning electron microscopy, infrared spectroscopy, and thermogravimetric analysis. The corrosion protection performance of microcapsule and epoxy varnish coatings with defect was tested by electrochemical impedance spectroscopy. Results showed that the microcapsule coating had a higher corrosion protection than epoxy varnish coating because capsule core acrylic resin could significantly improve the shield performance of the defect coating and capsule shell PANI could inhibit the corrosion reaction of magnesium alloy.