Effect of Graphene Oxide/ZSM-5 Hybrid on Corrosion Resistance of Waterborne Epoxy Coating

Waterborne Eco-Sustainable Sol-Gel Coatings Based on Phytic Acid Intercalated Graphene Oxide for Corrosion Protection of Metallic Surfaces

In the past few years, corrosion protection of metal materials has become a global challenge, due to its great economic importance. For this reason, various methods have been developed to inhibit the corrosion process, such as surface treatment approaches, by employing corrosion inhibitors through the deposition of opportunely designed functional coatings, employed to preserve from corrosion damages metallic substrates. Recently, among these techniques and in order to avoid the toxic chromate-based pre-treatment coatings, silane-based coatings and films loaded with organic and inorganic corrosion inhibitors have been widely used in corrosion mitigation water-based surface treatment. In this study, the synthetic approach was devoted to create an embedded, hosted, waterborne, and eco-friendly matrix, obtained by use of the sol–gel technique, through the reaction of functional alkoxysilane cross-linking precursors, namely (3-glycidyloxypropyl)trimethoxysilane (GPTMS) and (3-aminopropyl)triethoxysilane (APTES), in the presence of graphene oxide (GO) intercalated with natural and non-toxic phytic acid (PA) molecules. As a matter of fact, all experimental results from FT-IR spectroscopy, UV–Vis analysis, and SEM confirmed that PA molecules were successfully decorated on GO. Furthermore, polarization measurements and a neutral salt spray test were used to evaluate the anticorrosive performance on aluminum and steel substrates, thus showing that the GO-PA nanofiller improved the barrier and corrosion protection properties of the developed functional silane-based coatings.

Preparation, Characterization, and Evaluation of the Anticorrosion Performance of Submicron/Nanocarbon from Jute Sticks

Jute stick, one of the most commonly and abundantly available agricultural waste product, was converted to a value-added submicron/nano jute carbon by using pyrolysis and high-energy ball milling techniques. The submicron/nano jute carbon was characterized using FE-SEM, TEM, EDS, XRD, XPS and Raman spectroscopy. The anticorrosive performance of the submicron/nano jute carbon was investigated through electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP) and salt spray techniques, on mild steel plates coated with a mixture of epoxy resin and the submicron/nano jute carbon. The electrochemical impedance of the steel coated with the composite coating was two orders of magnitudes higher than that of the specimen coated with neat epoxy. Consequently, the corrosion rate of specimens coated with composite coating was 13-20 times higher than that of steel coated with neat epoxy coating. The salt spray results also indicate an improvement in the corrosion resistance performance of the composite coating compared to the neat epoxy. The uniform distribution of the submicron/nano jute carbon particles in the epoxy resin improved the denseness of the composite coating by acting as a barrier against the diffusion of chloride, moisture, and oxygen, thus, improving the corrosion resistance of the developed coating.

Dispersity control and anti-corrosive performance of graphene oxide modified by functionalized nanosilica in waterborne polyurethane

Graphene oxide (GO) is expected to be used in the field of waterborne polyurethane (WPU) anti-corrosive coatings due to its excellent barrier property, but the poor dispersibility of GO limits its application. The hydrophilic modification of GO, although improving its dispersity, will greatly reduce its anti-corrosive property. Here, a new method is provided to avoid seeking an appropriate modifier blindly. Via the interaction between the epoxy group and amine group, the aminated GO (NGO) can be modified by (3-glycidyloxypropyl) trimethoxysilane (KH560) functionalized-silica (f-SiO₂) nanoparticles, while the f-SiO₂ is affected by KH560 due to its relatively hydrophobic alkyl side chain. Consequently, the hydrophobicity of the f-SiO₂ modified NGO (f-SGO) can be regulated just by adjusting the amount of KH560, thereby achieving the balance of excellent dispersibility and anti-corrosive performance of the f-SGO nanosheets in the WPU. The electrochemical impedance and potentiodynamic polarization results showed that the anti-corrosive performance of the WPU hybrid was greatly improved by adding the appropriate amount of f-SGO. This research provides a new idea for GO application in waterborne coatings.

Preparation and Anti-Corrosive Properties of Waterborne Epoxy Composite Coating Containing Graphene Oxide Grafted with Sodium Tripolyphosphate

In this paper, graphene oxide (GO) was grafted with sodium tripolyphosphate (STP) to achieve a new anti-corrosive pigment (STG) with homogenous dispersion in waterborne epoxy (EP). The results obtained from Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and X-ray Diffraction (XRD) revealed that STP was successfully combined with GO by chemical bonding. The corrosion resistance of EP, GO/EP and STG/EP coatings on carbon steel substrates was investigated via electrochemical impedance spectroscopy (EIS) and salt spray test. The EIS results showed that the impedance value of coating with 0.7 wt.% STG reached 1.019 × 109 Ω∙cm2, which was considerably higher than that of neat waterborne EP coatings. Salt spray test results revealed once again that STG (0.7 wt.%)/EP coating had superior corrosion resistance. Besides, the STG (0.7 wt.%)/EP coated sample showed the highest adhesion strength between coating and substrate.

Phytic Acid Intercalated Graphene Oxide for Anticorrosive Reinforcement of Waterborne Epoxy Resin Coating

Epoxy resin coatings were prepared with phytic acid-doped graphene oxide (PA-GO) to modify epoxy resins (EP). The aim was to improve the dispersion of GO in waterborne epoxy resin, and thus to improve the corrosion resistance of steel structures. The Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) results showed that PA-GO was successfully prepared and has a better dispersion in epoxy resin. This is mainly due to the PA insert, which increased the layer spacing of the GO. The results obtained under the controlled corrosive environment showed that the specimen coated with EP containing 1.0 wt.% PA-GO had better corrosion resistance than other samples. This resistance was also two orders of magnitude higher than pure epoxy coating. The main reason for this is that the dispersion of GO in waterborne epoxy resin had been improved.

Reduced Graphene Oxide–Epoxy Grafted Poly(Styrene-Co-Acrylate) Composites for Corrosion Protection of Mild Steel

Reduced graphene oxide–epoxy grafted poly(styrene-co-acrylate) composites (GESA) were prepared by anchoring different amount of epoxy modified poly(styrene-co-acrylate) (EPSA) onto reduced graphene oxide (rGO) sheets through π–π electrostatic attraction. The GESA composites were characterized by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The anti-corrosion properties of rGO/EPSA composites were evaluated by electro-chemical impedance spectroscopy (EIS) in hydroxyl-polyacrylate coating, and the results revealed that the corrosion rate was decreased from 3.509 × 10−1 to 1.394 × 10−6 mm/a.

Synthesis of a Carrageenan-Iron Complex and Its Effect on Flame Retardancy and Smoke Suppression for Waterborne Epoxy

A k-carrageenan-iron complex (KC-Fe) was synthesized by complexation between degraded KC and FeCl3. Furthermore, KC-Fe and ammonium polyphosphate (APP) were simultaneously added into waterborne epoxy (EP) to improve its flame retardancy and smoke suppression performance. The structure and properties of KC-Fe were assessed using Fourier transform infrared spectroscopy (FTIR), ultraviolet (UV) spectroscopy, thermo gravimetric analysis (TGA), and X-ray powder diffraction analysis (XRD). The analysis showed that KC-Fe was successfully synthesized and exhibited good thermal properties with a 49% char residue at 800 °C. The enhanced flame retardancy and smoke suppression performance of waterborne epoxy were evaluated using a limiting oxygen index (LOI) and UL-94. Moreover, the flame retardancy of waterborne epoxy coated on a steel plate was also investigated using cone calorimetry. The results showed that the flame-retardant waterborne epoxy blend exhibited the best flame retardancy when the mass ratio of APP and KC-Fe was 2:1. The total heat release (THR) and total smoke production (TSP) was decreased by 44% and 45%, respectively, which indicated good fire safety performance and smoke suppression properties. Analysis of the residual char using FTIR, SEM, and elemental analysis (EDS) indicated that the action of KC-Fe was promoted by the presence of APP. The formation of a dense thermal stable char layer from an intumescent coating was essential to protect the underlying materials.

Study on a Novel Recyclable Anticorrosion Gel Coating Based on Ethyl Cellulose and Thermoplastic Polyurethane

In this paper, ethyl cellulose, thermoplastic polyurethane, and mineral oil were used as the main raw materials to synthesize a recyclable thermoplastic gel for anticorrosion coatings by a hot melt method. In addition, the effect of thermoplastic polyurethane on the properties of the coating was discussed. The structure and corrosion protection properties of the coating were characterized and analyzed by a scanning electron microscope, transmission electron microscope, X-ray diffraction, infrared spectroscopy, dynamic mechanical analysis, salt spray test, and electrochemical measurements. The results show that the ethyl cellulose and oil in the coating can form a stable organic-gel structure by hydrogen bonding, and the mineral oil and castor oil are uniformly dispersed in the coating. The surface of the coating does not change after 3000 h of a salt spray test. During the repeated hot melting spraying and immersion in 3.5 wt.% NaCl solution for five times, the electrochemical impedance modulus of the coating was always above 109 Ω⋅cm2, the water absorption rate was always less than 1.5 wt.%, and the mechanical properties of the coating did not decrease. This novel coating could be used for the corrosion protection of flange and valve connections in pipeline and bolting connections in different industries. The disassembly and assembly operation of these connection structures during the regular maintenance will destroy the ordinary anticorrosion coating, and the irregular geometric shape of such places also make difficulties for the preparation of ordinary coatings onsite.

Synthesis of Phosphated K-Carrageenan and Its Application for Flame-Retardant Waterborne Epoxy

In this paper, phosphated K-carrageenan (P-KC) was obtained by reacting POCl₃ with the renewable source K-carrageenan (KC). P-KC and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) were added into waterborne epoxy (EP) to improve its flame retardancy. The structure of P-KC was studied comprehensively using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), thermo-gravimetric analysis (TGA), showing the successful synthesis of P-KC. The flame retardancy of the EP was evaluated by the cone calorimeter test. The results showed that different mass ratios of DOPO and P-KC affected the flame retardancy of EP. When the mass ratio of DOPO and P-KC was 2:1, total heat release (THR) and total smoke production (TSP) decreased by 48.7% and 37.4%, respectively. The microstructures of residue char were observed by FTIR and scanning electron microscopy (SEM), indicating that the flame-retardant waterborne epoxy (FR-EP) system held a more cohesive and denser char structure. The char inhibited the diffusion of heat and oxygen, which played a key role in the flame retardancy.