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The ecofriendly waterborne alkyd coatings generally compromise the coating performance. Incorporation of polyaniline into alkyd to form nanocomposites can improve the corrosion resistance; however, the uniform distribution of polyaniline (PANI) within the alkyd resin remains a challenge. In this work, PANI is grafted onto epoxy functionalized phosphorylated poly (vinyl alcohol) (PPVA) with different side-chain configurations in order to improve compatibility and dispersion stability. These functionalized PPVA are synthesized using epichlorohydrin (ECIP) or γ-glycidyl methacrylate (GMA) as modifying agents, and respectively labeled as E-PPVA and G-PPVA. G-PPVA/PANI dispersion is stable even at a high PANI loading of 50%, while the maximum PANI loading for E-PPVA/PANI is only 30%. With the incorporation of G-PPVA/PANI into waterborne alkyd resins (AR), the coating resistance is increased by 7 orders of magnitude, and the corrosion inhibition efficiency is up to 99.9%. The coating with the incorporation of G-PPVA/PANI also demonstrates superior long-term corrosion resistance in comparison with that AR/E-PPVA/PANI nanocomposite coating.

Graphitic carbon nitride (g-C3N4) has been considered as a candidate for anti-corrosion material owing to its barrier property and photoelectrochemical cathodic protection. However, the related mechanisms remain obscure and are not fundamentally investigated. Herein, g-C3N4 coating on Q235 CS plate matrix can be simply made via conductive adhesive, which helps to achieve scalable production and high cost-effectiveness. It can also ensure the unidirectional transfer of excited electrons from g-C3N4 to metal to prevent the consumption of free electrons on metal and reduce Fe2O3 onto Fe. During the photocatalytic anti-corrosion process, the electron holes were simultaneously consumed via oxidizing water to achieve the balance between electron and hole transport. By combining theoretical calculation and experimental analysis, the anti-corrosion mechanisms of g-C3N4 were systematically investigated. g-C3N4 displayed superior long-term and remote anti-corrosion properties, especially for remote and difficult-to-reach areas, which will make it become a new generation of anti-corrosion 2D material with promising performance.

Graphene oxide/polyaniline (GO/PANI) has been demonstrated to be an effective anti-corrosive nanofiller in polymer matrix, however, its hydrophobility restricts its application in waterborne polymer coatings. Here, cetyltrimethylammonium bromide (CTAB) and cationic gemini surfactant (GS) with the same constitutional unit as CTAB were adopted to fabricate CTAB modified GO/PANI (CGO/PANI) and GS modified GO/PANI (GGO/PANI). The incorporation of GS not only increased the intercalation degree of GO nanosheets but also functionalized as dopant to improve the electrochemical properties of PANI. The dispersibility and compatibility of GGO/PANI in waterborne alkyd resin (WAR) were also higher than that of CGO/PANI, resulting in the formation of more uniform nanocomposite coating. Compared with pure WAR, the coating resistance of GGO/PANI/WAR increased by 4 orders of magnitude, the corrosion density decreased by 3 orders of magnitude and the corrosion potential shifted from −0.72 V to −0.28 V. GGO/PANI/WAR also displayed enhanced long-term anti-corrosive properties in comparison with CGO/PANI/WAR.

Diisocyanates functionalized graphene nanosheets with high level exfoliation have been demonstrated as effective anticorrosion fillers in waterborne polymer coatings. However, diisocyanates can cause potential environmental and health hazard. Here, we propose to use polyiscocyanate (Tri-HDI) with an isocyanurate-ring structure yet low volatility and toxicity, to functionalize reduced graphene (RGO). Compared with hexamethylene diisocyanate (HDI), the incorporation of Tri-HDI simultaneously increased the exfoliation degree and the dispersibility of RGO. The reactivity between Tri-HDI and GO was also enhanced, resulting in the increase of graft ratio. The addition of Tri-HDI-RGO (Tri-HDIG) was able to improve the colloidal stability of waterborne epoxy resin (ER), as well as the interaction and compatibility between Tri-HDIG and ER. The tensile strength of ER/Tri-HDIG thereby increased from 50.1 MPa to 81.8 MPa, and the water absorption decreased from 18.0 % to 5.90 %. The long-term corrosion resistance of ER/Tri-HDIG also got significant improvement, its impedance modulus increased by 5 orders of magnitude compared to pure ER coating. The broad applicability of Tri-HDIG as functional nanofiller in polymer matrixes has been confirmed.

The compatibility between polypyrrole (PPy) and waterborne epoxy coating (EP) remains the main challenge. Here, phosphorylated poly (vinyl alcohol) (PPVA) and p-toluene sulfonic acid sodium (p-TSA) were simultaneously utilized as dopants to modify PPy and prepare water dispersible PPVA/p-TSA/PPy (PPVAT/PPy) solution. Additionally, poly (vinyl alcohol) (PVA) and TSA were also adopted to prepare PVA/p-TSA/PPy (PVAT/PPy) for comparison. Denser film with granular morphology was observed for PPVAT/PPy nanocomposite film. Compared with PVAT/PPy-40 %, the tensile strength of PPVAT-8.0 %/PPy-40 % increased from 248.8–283.9 MPa. PPVAT/PPy displayed higher compatibility and interactions with EP compared to PPy-TSA and PVAT/PPy. Compared with EP, the impedance modulus of PVAT/PPy+EP and PPVAT/PPy+EP increased from 3.17×105 to 1.07×108 and 1.62×109 Ω·cm2; corrosion current density Icorr decreased from 1.49×10−6 to 7.72×10-8 and 4.01×10-9 A·cm-2; corrosion potential Ecorr displayed a positive shift of 230 mV and 269 mV, respectively. The corrosion inhibition efficiency of PPVAT/PPy+EP reached 99.83 %, which is much higher than that of PVAT/PPy+EP (93.97 %). PPVAT/PPy+EP nanocomposite coating has been proved to have preferable long-term corrosion resistance based on electrochemical impedance spectra (EIS), polarization curves and salt water spray test. The simultaneous incorporation of phosphate anions, sulfate ions and PPy into EP was beneficial to fabricate high-performance anticorrosion coating.

Waterborne polyurethane (WPU) has been intensively utilized as host materials for intrinsic conducting polymers. However, the stability and compatibility between polyaniline (PANI) and WPU remain a challenge for their composites. In this research, anionic–nonionic sulfonated waterborne polyurethane (SWPU) is adopted as matrix to prepare nanosized PANI-g-SWPU dispersions through chemical graft polymerization method, and the stability mechanism is systematically investigated. The PANI-g-SWPU dispersion is endowed with much higher stability and no PANI precipitation is detected after storage for 1 year when the PEG molecular weight is 1000 and R value is 1.2. The surface resistivity reaches the minimum when the graft time is 2.5 h, pH value is 2, n(APS)/n(aniline) is 1, and the aniline content is 20 wt %. And the resistivity of the coated paper reaches 1.39 Ω cm, indicating that the as-prepared PANI-g-SWPU dispersion can be directly used as the antistatic coatings, which is also suitable for large scalable production. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45412.