Shihui Qiu

Synergistic Effect of Polypyrrole-Intercalated Graphene for Enhanced Corrosion Protection of Aqueous Coating in 3.5% NaCl Solution

Dispersion of graphene in water and its incorporation into waterborne resin have been rarely researched and hardly achieved owing to its hydrophobicity. Furthermore, it has largely been reported that graphene with impermeability contributed to the improved anticorrosion property. Here, we show that highly concentrated graphene aqueous solution up to 5 mg/mL can be obtained by synthesizing hydrophilic polypyrrole (PPy) nanocolloids as intercalators and ultrasonic vibration. On the basis of π-π interaction between PPy and graphene, stacked graphene sheets are exfoliated to the thickness of three to five layers without increasing defects. The corrosion performance of coatings without and with PPy and graphene is obtained by potential and impedance measurements, Tafel curves, and fitted pore resistance by immersing in a 3.5 wt % NaCl solution. It turns out that composite coating with 0.5 wt % graphene additive exhibits superior anticorrosive ability. The mechanism of intercalated graphene-based coating is interpreted as the synergistic protection of impermeable graphene sheets and self-healing PPy and proved by the identification of corrosion products and the scanning vibrating electrode technique.

In situ polymerization of sulfonated polyaniline in layered double hydroxide host matrix for corrosion protection

The hybrid material of sulfonated polyaniline/Mg Al layered double hydroxides (SPANi/LDHs) was obtained through polymerization of o-aminobenzenesulfonic acid and aniline in the galleries of LDHs. The structure of SPANi/LDH was characterized by field-emission scanning electron microscopy, X-ray diffraction, Fourier transformed infrared and Raman spectroscopy. The as-prepared SPANi/LDH showed an irregular lamellar shape with an average diameter of 4–6 μm and offset of XRD reflections, which revealed that SPANi successfully grew between the LDH interlayers and expanded the interlayered structure slightly. Besides, the monolayer thickness of the SPANi/LDH was about 2.67 nm, which exhibited a significant structure of a nanosheet. The as-prepared SPANi/LDHs hybrids were applied to waterborne epoxy coatings for steel substrates and exhibited significant corrosion protection capacities compared with those of neat epoxy and pure SPANi blended epoxy composites. The electrochemical impedance spectroscopy (EIS) technique was used to describe the electrochemistry dynamics and remarkable corrosion protection performance. Furthermore, corrosion products beneath the epoxy coatings immersed in a 3.5 wt% NaCl aqueous solution were also investigated, which indicated the barrier property and passivation effect of SPANi/LDH. In addition, the mechanism of corrosion inhibition was explored via the analysis of rust layers, and the barrier effect and passivation effect of the composite materials was also demonstrated.

Dopamine@Nanodiamond as novel reinforcing nanofillers for polyimide with enhanced thermal, mechanical and wear resistance performance

In this study, to achieve a homogeneous dispersion of nanodiamond (ND) in a polyimide (PI) matrix and a strong interfacial adhesion between ND and the PI matrix, a biomimetic nondestructive dopamine chemistry was employed for surface modification of ND. FTIR and Raman spectroscopy studies revealed that self-polymerization of dopamine could produce thinner polydopamine (PDA) layers on the ND surface via spontaneous oxidation and the intermolecular cross-linking reaction of PDA molecules. The structure and morphology of PDA–ND were studied by FTIR, SEM, and Raman spectroscopy, which verified the π–π interactions between PDA and ND. The facile dispersion of PDA–ND in a polyamic acid prepolymer made it possible to obtain PI/ND composites with no obvious ND aggregation. The effect of PDA–ND nanoparticles on the thermal, mechanical and tribological properties of the resulting PI/PDA–ND composites were evaluated, and the results showed that the incorporation of PDA–ND could increase the hardness, tensile strength, storage modulus, as well as the wear resistance properties. PI/PDA–ND composites prepared in this study showed that PDA–ND is a promising nanoreinforcing filler for PI composites.

Anticorrosive behavior of a zinc-rich epoxy coating containing sulfonated polyaniline in 3.5% NaCl solution

An epoxy zinc-rich composite coating containing self-doped conducting sulfonated polyaniline (SPANi) nanofiber was prepared and the corrosion resistance of as-prepared coatings on Q235 substrate studied by open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and scanning vibrating electrode technique (SVET). Results suggested that a zinc-rich coating with addition of 1.0 wt% SPANi could enhance the cathodic protection time and barrier performance. To study corrosion diffusion, artificial scratch and adhesion strength were investigated via the salt spray test and pull-off test, respectively. Finally, the passivating action of coatings was demonstrated by analyses of corrosion products via X-ray diffraction spectroscopy.