Tapan Kumar Rout

Development of conducting polyaniline coating: a novel approach to superior corrosion resistance

Abstract The present work was undertaken to study the corrosion behaviour of conducting polymer coating on ferrous material. The synthesis of polyaniline (PAni) powder, its characterization, blending and coating formulation are described in details. The yield of synthesized polymer was approximately 90% with a conductivity of 0.20–0.40 S/cm. The coating was formulated by incorporating this PAni powder as pigment. The coating conductivity increased with increase in the solid concentration and saturated in the range of 10–15 wt.%. The results of the corrosion tests on PAni coated steel substrate with 1–50 μm coating thickness exposed to 3.5% NaCl solution were also presented. The corrosion resistance of PAni coated steel was found to be more than 10–15 times higher than the bare steel. Electrochemical impedance spectroscopy study revealed that a continuous charge transfer reaction across the metal–coating interface was responsible for the increase in coating capacitance and decrease in polarization resistance. The potentiodynamic study also showed that the current density significantly decreased in PAni coated steel in comparison to bare steel.

Effective Piezoelectric Response of Substrate-Integrated ZnO Nanowire Array Devices on Galvanized Steel

Harvesting waste energy through electromechanical coupling in practical devices requires combining device design with the development of synthetic strategies for large-area controlled fabrication of active piezoelectric materials. Here, we show a facile route to the large-area fabrication of ZnO nanostructured arrays using commodity galvanized steel as the Zn precursor as well as the substrate. The ZnO nanowires are further integrated within a device construct and the effective piezoelectric response is deduced based on a novel experimental approach involving induction of stress in the nanowires through pressure wave propagation along with phase-selective lock-in detection of the induced current. The robust methodology for measurement of the effective piezoelectric coefficient developed here allows for interrogation of piezoelectric functionality for the entire substrate under bending-type deformation of the ZnO nanowires.

Graphene oxide and functionalized multi walled carbon nanotubes as epoxy curing agents: a novel synthetic approach to nanocomposites containing active nanostructured fillers

A novel synthetic approach is developed wherein graphene oxide and oxidized multiwalled carbon nanotubes are used as curing agents to induce cross-linking of an epoxy resin, thereby yielding a nanostructured epoxy composite with excellent dispersion of the carbon nanomaterials. This method allows for incorporation of up to 50 wt% of carbon nanomaterials within the polymeric matrix. The combination of covalent bonding and π–π interactions ensure excellent dispersibility of the nanomaterials within the polymeric matrix. These nanocomposites offer an alternative to the hazardous high-temperature fluorination and amine curing reactions that are usually required to formulate epoxy composite systems. Structural, mechanical, and morphological characterization of the composite material confirms the distribution, integrity, and potential to resist corrosion on a steel surface while also indicating the excellent adhesion and flexibility of the nanocomposite coatings.

Corrosion behavior of nanohybrid titania–silica composite coating on phosphated steel sheet

Corrosion resistance behavior of sol–gel-derived organic–inorganic nanotitania–silica composite coatings was studied. Hybrid sol was prepared from Ti-isopropoxide and N-phenyl-3-aminopropyl triethoxy silane. The structure, morphology, and properties of the coating were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermo gravimetric analysis. The corrosion performances of the sol–gel-coated samples were investigated by electrochemical impedance spectroscopy (EIS) and standard salt spray tests. The hybrid coatings were found to be dense, more uniform, and defect free. In addition, the coatings also proved its excellent corrosion protection on phosphated steel sheet.

Preparation of graphene oxide by dry planetary ball milling process from natural graphite

Graphene oxides (GO) with different degrees of oxidation have been prepared by an in-house designed horizontal high energy planetary ball milling process. The prepared graphene oxides have been studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) with selected area electron diffraction (SAED), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), micro Raman spectroscopy, Fourier transform infrared (FTIR) spectra, Brunauer–Emmett–Teller (BET) test and thermogravimetric analysis (TGA). XPS study shows an increasing trend of atomic concentration ratio of O/C with increasing ball milling time duration from 2 to 24 h of high purity graphite sample (FEED). This result is attributed to the formation of more oxidation in the graphite sample, produced due to the increasing time duration of milling. From micro Raman analysis it is also noted that ID/IG ratio increases with increasing milling time of FEED, which further supported the preparation of graphene oxide. In this study the graphene oxide prepared by 16 h of milling may be considered as the optimized sample as far as the degree of oxidation, time and energy consumption factors are concerned.

Anodized Steel Electrodes for Supercapacitors

Steel was anodized in 10 M NaOH to enhance its surface texture and internal surface area for application as an electrode in supercapacitors. A mechanism was proposed for the anodization process. Field-emission gun scanning electron microscopy (FEGSEM) studies of anodized steel revealed that it contains a highly porous sponge like structure ideal for supercapacitor electrodes. X-ray photoelectron spectroscopy (XPS) measurements showed that the surface of the anodized steel was Fe2O3, whereas X-ray diffraction (XRD) measurements indicated that the bulk remained as metallic Fe. The supercapacitor performance of the anodized steel was tested in 1 M NaOH and a capacitance of 18 mF cm(-2) was obtained. Cyclic voltammetry measurements showed that there was a large psueudocapacitive contribution which was due to oxidation of Fe to Fe(OH)2 and then further oxidation to FeOOH, and the respective reduction of these species back to metallic Fe. These redox processes were found to be remarkably reversible as the electrode showed no loss in capacitance after 10000 cycles. The results demonstrate that anodization of steel is a suitable method to produce high-surface-area electrodes for supercapacitors with excellent cycling lifetime.

Effect of molybdate coating for white rusting resistance on galvanized steel

Purpose – Chromium based conversion coatings have been used widely to delay the formation of white rust on galvanized steel sheets. As chromium is carcinogenic, an alternative chromium‐free conversion coating was developed for use on galvanized steel surfaces to delay the onset of white rusting. This paper seeks to address this issue.Design/methodology/approach – The molybdate coating was produced on galvanized steel surface by dipping in a phosphate solution bath using Na2MoO4 as a corrosion inhibitor.Findings – The cyclic polarization tests conducted on molybdates‐treated samples showed a wider potential band in 3.5 per cent NaCl solution, indicating that the coating is passivating in nature. The polarization (Rp) of both treated and untreated samples was evaluated in 3.5 per cent NaCl solution by electrochemical impedance spectroscopy (EIS) technique. It was observed that the polarization resistance (Rp) of molybdate treated galvanized sample is 2.3 times higher compared with the untreated one. The imp...

Electron Transfer Directed Antibacterial Properties of Graphene Oxide on Metals

Nanomaterials such as silver nanoparticles and graphene-based composites are known to exhibit biocidal activities. However, interactions with surrounding medium or supporting substrates can significantly influence this activity. Here, it is shown that superior antimicrobial properties of natural shellac-derived graphene oxide (GO) coatings is obtained on metallic films, such as Zn, Ni, Sn, and steel. It is also found that such activities are directly correlated to the electrical conductivity of the GO-metal systems; the higher the conductivity the better is the antibacterial activity. GO-metal substrate interactions serve as an efficient electron sink for the bacterial respiratory pathway, where electrons modify oxygen containing functional groups on GO surfaces to generate reactive oxygen species (ROS). A concerted effect of nonoxidative electron transfer mechanism and consequent ROS mediated oxidative stress to the bacteria result in an enhanced antimicrobial action of naturally derived GO-metal films. The lack of germicidal effect in exposed cells for GO supported on electrically nonconductive substrates such as glass corroborates the above hypothesis. The results can lead to new GO coated antibacterial metal surfaces important for environmental and biomedical applications.

High performance chrome free coating for white rust protection of zinc

Development of chrome free coatings for white rust (corrosion) protection of galvanised steel is a key concern for scientists worldwide. The present work presents the results of an investigation on the effect of amine and thiol functional groups bearing silane coupling agents such as 3-phenyl-aminopropyl-triethoxy silane and mercapto-propyl-tri methoxysilane respectively on anticorrosion properties of a reference sol–gel solution. Anticorrosion performance of the coatings was evaluated by potentiodynamic polarisation method and AC impedance spectroscopy. Accelerated corrosion test was performed using salt spray chamber and compared with a chromate coated galvanised sheet. The results clearly revealed that the addition of silane containing thiol group to the reference coating solution produced remarkable improvement in hydrophobicity and corrosion resistance compared to amine group.

Development of Epoxy based Surface Tolerant Coating Improvised with Zn Dust and MIO on Steel Surfaces

Couple of high strength and flexible surface tolerant coatings were designed for oil contaminated, rusty, and minimally prepared steel surfaces. These coatings are to have strong interfacial adhesion due to low surface tension and sustain more than 5 MPa pull out force consistently. The effect of optimized concentration of zinc dust and micaceous iron oxide (MIO) as pigments is evaluated for these surface tolerant coating systems. It has been noticed that the presence of these two ingredients has enhanced corrosion resistance more than several times as compared to commercially available coating systems. The corrosion simulation test in 3.5 wt.% NaCl has evident for significant improvement in terms of delaying blistering and delamination. The high pore resistance ( ) indicates the slow migration of ions and water into the substrate and coating interface, which could be the reason of the improvement in corrosion process.