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The corrosion protection and electrochemical mechanism of solvent-borne alkyd composite coating containing 1.0 wt.% polyaniline (PANI) and 1.0 wt.% CeO2 nanoparticles (NPs) for carbon steel in 3.0 wt.% NaCl solution were investigated by means of scanning electron microscopy (SEM), ex-situ, in-situ and electrochemical controlled (EC) atomic force microscopy (AFM), open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) methods. The SEM and ex-situ AFM results revealed the micro- and nanostructure of the composite coating. The in-situ sequential AFM images and line profiling analysis indicated electrochemical activity of the NPs and a high stability of the composite coating in NaCl solution. The results of EC-AFM combined with cyclic voltammetry (CV) demonstrated volume change of the PANI NPs upon reduction and oxidation at certain applied potentials on the coating. The redox reactions between the different forms of PANI and the effect of the CeO2 NPs on the polymerization of the composite polymer were further confirmed by infrared reflection absorption spectroscopy (IRAS). The OCP and EIS results revealed that the composite coating provided an improved corrosion protection for carbon steel within several days of exposure, which was attributed to the barrier protection of CeO2 NPs and the passivation ability of PANI.

This article reports the potential use of Polypyrrole (PPy) particles as anticorrosive additive on an epoxy water-based paint to increase the corrosion protective property of aluminum-coated panels. AA1200 aluminum panels were painted using the electrophoretic deposition method and the coatings with different concentrations of PPy particles were tested. PPy particles were synthetized by oxidative polymerization of pyrrole (Py) with iron (III) chloride hexahydrate (FeCl3.6H2O) in the presence of dodecylbenzenesulfonic acid (DBSA). Electrically conducting PPy particles (6.5 S cm–1) were obtained with a size average of 154 nm. The as-prepared PPy particles were added into a water-based epoxy paint and AA1200 panels were coated via electrophoretic deposition method. The corrosion protective properties of e-coated AA1200 panels were evaluated by means of electrochemical impedance spectroscopy over prolonged exposure time in neutral non-aerated 0.1 M sodium chloride NaCl electrolyte. In particular, the addition of 0.4% by weight PPy has improved the coating corrosion protective property with respect to epoxy clearcoat and exhibited the highest value of impedance modulus at low frequency among the studied coatings.

3-D printed samples based on acrylonitrile-butadiene-styrene (ABS) loaded with multi-walled carbon nanotubes (CNT), carbon black (CB) and a 50:50 hybrid combination (CNT/CB) were manufactured via fused deposition modelling (FDM). The electromagnetic interference shielding efficiency (EMI SE) of resulting FDM specimens was assessed. Different amounts of CNT, CB and CNT/CB were dispersed in an ABS matrix by melt compounding using an internal mixer. On the basis of the rheological behavior a weight fraction of 3% was selected for the filaments production. The filaments were prepared using a twin-screw extruder and used to feed a commercial FDM machine for 3-D printed specimen's preparation along three different growing directions. The electrical conductivity, the EMI SE and the mechanical properties of the resulting extruded filaments, as well as the 3-D printed specimens, were measured and, they are discussed in terms of the type of filler and growing directions. In general, the conductivity, EMI SE and mechanical properties of 3D printed parts were markedly dependent on the growing direction. Through the experimental findings of this work, an appropriate choice of a polymer nanocomposite formulation alongside the 3-D printing parameters could lead to components manufactured via FDM with optimized EMI SE and mechanical properties.

In this study, nanostructured composite based on Montmorillonite-Polypyrrole (Mt-PPy) was prepared via in situ chemical polymerization of Pyrrole in presence of Mt and dodecyl benzene sulfonic acid (DBSA). Subsequently, the as-prepared Mt-PPy additive as well as pure Mt and PPy were incorporated into an epoxy coating as anticorrosive protection additives for low carbon steel. The electrical conductivity, chemical changes and microstructure of the as-prepared electrically conductive additives were investigated. Steel coated specimens were prepared via solvent cast method and the anticorrosion protection ability of the coatings was evaluated by means of electrochemical impedance spectroscopy (EIS). Likewise, surface features of the coatings such as contact angle and roughness were examined. Due to the higher aspect ratio and ease of dispersion of Mt-PPy epoxy coatings loaded with Mt-PPy additives exhibited higher electrical conductivity values with respect to those containing merely PPy. Besides, contact angle (CA) between deionized water and Epoxy/Mt-PPy coated carbon steel was higher than CA for neat epoxy whereas CA of Epoxy/PPy and Epoxy/Mt were significantly reduced. EIS measurements revealed higher impedance values for Epoxy/Mt-PPy coating; the outputs of EIS suggested enhanced barrier property of epoxy coating when Mt-PPy additive was added. The results observed in this study are pointing towards the prospective use of the Epoxy/Mt-PPy with 5 wt% content as a corrosion protective coating for carbon steel.

Metals are mostly painted to improve corrosion protection of the coated item. Nevertheless, paints can be used to deliver visual aspects to them. Several investigations were conducted to comprehend color variation of paints as function of accelerated tests however, limited information is found concerning these variations versus field exposure. Thus, there is the interest to cover this lack of information and investigate color changes of waterborne paints versus field exposure. In this study colored styrene-acrylic painted steel panels were naturally aged in the alpine climate of Trento, northern of Italy. Color measurements were conducted according to the CIEL*a*b* standard. Gloss measurements and FT-IR spectroscopy assessed variations on the surface topography and chemical structure of the coated panels. It was observed that the changes in color of the colored paints were commanded by the interaction of ultraviolet radiation and they were dependent on the chemical nature of the color pigments. In addition, in the months with attenuated solar irradiance and predominance of TOWISO conditions, gloss reduction rates and L* of the coated panels have their evolution trend shifted. Upon accelerated UV.B ageing conducted in dry condition neither fluctuations on the L* nor attenuation on the gloss reduction rates were detected. Keywords: Waterborne paints, Styrene-acrylic, Natural ageing, Accelerated ageing, Color variation

Organic coatings are extensively used in many fields of engineering such as automotive or architectural industries for protection of the metallic structure against corrosion and to deliver visual aspects to the coated item. High quality paints either for outdoor or indoor applications require longer stability of their visual appearance alongside maintenance on the corrosion protection ability. In the present work, the total color variation and corrosion protection efficiency of waterborne styrene-acrylic paints loaded with different contents of organic yellow pigment has been studied. The paints have been deposited via cathodic electrodeposition on cold rolled steel. The visual aspect’s stability of the paints was monitored as function of field exposure wherein the painted panels were naturally aged throughout one solar year in the alpine environment of Trento − northern of Italy. Color measurements were conducted according to the CIEL*a*b* color standard and gloss measurements alongside FT-IR spectroscopy were used to assess variations on the surface topography and chemical structure of the coated panels. It has been observed that solar radiation, the relatively humidity and temperature played a role on the surface roughness as well as on the lightness aspects of the coated panels. The electrochemical impedance spectroscopy outcomes revealed a dependency of the barrier properties of the paints with the pigment concentration. Superior barrier properties were verified for the paints with pigment content lower than 1.0 wt.%.

In this paper, Ni Mo alloy coatings were deposited from bath containing sodium citrate, nickel sulphate, and sodium molybdate. Essentially, this work is divided into two mains parts: (i) the optimization on the coatings deposition parameters and (ii) the effect of the heat treatment. Polarization curves and electrochemical impedance spectroscopy were acquired using potentiostat/galvanostat and a frequency response analyzer, respectively. Morphology and chemical composition of the coatings were investigated by scanning electron microscopy and energy dispersive spectroscopy, respectively. Polarization curves at different condition revealed that electroplating at temperature 40 o C, pH 9 provides a dense coating with high efficiency. Following the optimization of the deposition parameters, the coatings were annealed at 200, 400, and 600 o C for 25 min. The results showed that the coatings obtained at temperature 40 o C, pH 9, and annealing at 600 o C has the highest corrosion resistance and microhardness.

A composite solvent-borne alkyd coating with 1 wt% p-toluene sulfonic acid (PTSA) doped polyaniline (PANI) was prepared. The mechanisms of electrochemical activity and self-healing properties of the composite coating were investigated by in situ atomic force microscopy (AFM), intermodulation AFM (ImAFM), electrochemical controlled (EC)-AFM combined with cyclic voltammetry (CV), Kelvin force microscopy (KFM), and Fourier transform infrared spectroscopy (FTIR), as well as open-circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) methods. The ImAFM demonstrates the multiphase structure of the composite coating and a high compatibility between the doped PANI and alkyd matrix. The CV and EC-AFM results reveal a high electrochemical activity of the doped PANI in the composite coating as well as reversible redox reactions between the emeraldine salt (ES) and leuco emeraldine base (LB) forms. The Volta potential mapping of KFM demonstrates a strong self-healing ability of the doped PANI in air conditions. The good electrochemical connection between the fine network of PANI in the composite coating and metal surface underneath enable the occurrence of reversible redox reaction between the ES/LB forms of doped PANI and a concomitant release of dopant anions both in air and in 3 wt% NaCl solution as demonstrated by OCP and EIS results. These therefore lead to the strong passivation and self-healing effect of the composite coated on the carbon steel surface.

The present work reports on the production and characterization of acrylonitrile butadiene styrene (ABS) hybrid nanocomposite filaments incorporating graphene nanoplatelets (GNPs) and carbon nanotubes (CNTs) suitable for fused filament fabrication (FFF). At first, nanocomposites with a total nanofiller content of GNP and/or CNT of 6 wt.% and a GNP/CNT relative percentage ratio of 0, 10, 30, 50, 70, and 100 were produced by melt compounding and compression molding. Their mechanical, electrical resistivity, and electromagnetic interference shielding effectiveness (EMI SE) properties were evaluated. The hybrid nanocomposites showed a linear increase in modulus and decrease in strength as a function of GNP content, on the other hand, the addition of CNT in hybrid nanocomposites determined a positive increase in electrical conductivity, but a potentially critical decrease of melt flow index. Due to the favorable compromise between processability and enhancement of performance (i.e., mechanical and electrical properties), the hybrid composition of 50:50 GNP/CNT was selected as the most suitable for the filament production of 6 wt.% carbonaceous nanocomposites. EMI SE of ABS-filled single CNT and hybrid GNP/CNT nanofillers obtained from compression molding reached the requirement for applications (higher than &minus, 20 dB), while slightly lower EMI SE values (in the range &minus, 12/&minus, 16 dB) were obtained for FFF parts dependent on the building conditions.

A solventborne alkyd composite coating containing modified montmorillonite (MMT) nanoclay was made on carbon steel, and its corrosion protection was investigated by in-situ atomic force microscopy (AFM) and electrochemical impedance spectroscopy (EIS) measurements in 3 wt.% NaCl solution. X-ray diffraction (XRD) analysis indicated intercalation of the MMT sheets in the composite coating. Thermo-gravimetric analysis (TGA) demonstrated improved thermal stability of the composite coating due to the modified nanoclay. Scanning electron microscopy (SEM) and AFM examination revealed dispersion and also some aggregation of the nanoclay particles in the coating. In-situ AFM images show a stable coating surface at nano-scale during relative long time exposure in the NaCl solution, indicating an enhanced stability of the composite coating. The EIS results confirmed that the composite coating provides an enhanced barrier type corrosion protection for carbon steel in the corrosive solution, which could be attributed to the intercalated lamellar MMT sheets in the coating that block the defects and decrease the transport of water and corrosive species. QC 20150820

The corrosion protection of a waterborne acrylic composite coating with 1 wt% ceria nanoparticles (CeNP) coated on carbon steel in 3 wt% NaCl solution was investigated by ex-situ and in situ as wel ...

In the search for viable alternatives to produce environmentally friendly organic coatings systems, this work presents the study of several inorganic anticorrosive inhibitors and their further incorporation into a polymeric matrix via powder coating technology. The selected inhibitors are commercially available belonging to the second and third generations of developed replacement alternatives for hazards chromates. Polarization curves, also in the presence of continuous flow of N2 and air gases, have been used for the characterization of the inhibitors. Succeeding, the inhibitors were embedded in powder coatings and subsequently applied onto mild steel substrate. The coated panels have been investigated by means of accelerated tests (neutral salt spray test, cathodic delamination test), natural weathering alongside electrochemical techniques such as electrochemical impedance spectroscopy. The effectiveness of the different corrosion inhibition pigments in the organic coatings has been evaluated and discussed.

Various processes can occur when paints are in contact with moisture, such as ingress of water and aggressive ions into the coating. As a consequence, the microstructure and properties of the paints can be affected. The present study combines electrochemical impedance spectroscopy (EIS) and in situ atomic force microscopy (AFM) to investigate the barrier property of waterborne and solventborne coatings on mild steel, paying particular attention to the occurrences in the first 24 h after contact between the coating surface and electrolyte. The sequential in situ AFM images revealed that changes on the order of hundreds of nanometres at the coating surface have occurred shortly after the exposure to the electrolytes. EIS observations for the clear waterborne alkyd coating revealed a rise in the |Z|0.015Hz and a decrease in the coating capacitance after a few hours of exposure. Evidences that water uptake caused swelling of the coating and promoted the closure/blockage of pores were given by means of in situ AFM. The solventborne alkyd emulsion has demonstrated lower reactivity to the presence of the electrolyte and a correlation between the coating resistance and defects/pores evolution is suggested.

A study of the anticorrosive properties of an alkyd coating loaded with polyaniline and cerium oxide (CeO 2 ) nanoparticles is presented in this paper. Investigated by means of Electrochemical Impedance Spectroscopy and accelerated salt spray test, the blank alkyd coating has been loaded with PAni, ceria nanoparticles and the combination of both with 1.0 wt.% content. Through the monitoring of open circuit potential, an ennoblement effect was detected for the systems in the presence of a mild solution. Moreover, EIS evolution of the alkyd containing polyaniline revealed a stable performance of the system in the presence of sulphate solution, whereas for those containing ceria nanoparticles a considerable raise in the | Z | 0.015 Hz , from 10 7 to 10 8 Ω cm 2 in the course of 24 h of immersion, an increasing trend of the charge transfer resistance during the equivalent period of exposure was observed. Furthermore, the anticorrosive contribution given by the ceria nanoparticles is supported by the accelerated salt spray test which revealed lower delamination rates. In the case of the alkyd loaded with polyaniline and ceria nanoparticles simultaneously the evidences are less perceived by means of electrochemical analysis, however, from salt spray tests it can be seen that the influence of the mixture is promising at a certain extent.

Acrylonitrile–butadiene–styrene (ABS) filled with 6 wt.% of multi-walled carbon nanotubes and graphene nanoplatelets was extruded in filaments and additively manufactured via fused deposition modeling (FDM). The electrical conductivity and electromagnetic interference shielding efficiency (EMI SE) in the frequency range between 8.2 and 12.4 GHz of the resulting 3D samples were assessed. For comparison purposes, compression molded samples of the same composition were investigated. Electrical conductivity of about 10−4 S·cm−1 and attenuations of the incident EM wave near 99.9% were achieved for the 3D components loaded with multi-walled carbon nanotubes, almost similar to the correspondent compression molded samples. Transmission electron microscopy (TEM) images of ABS composite filaments show that graphene nanoplatelets were oriented along the polymer flow whereas multi-walled carbon nanotubes were randomly distributed after the extrusion process. The electrical conductivity and electromagnetic interference (EMI) shielding properties of compression molded and FDM manufactured samples were compared and discussed in terms of type of fillers and processing parameters adopted in the FDM process, such as building directions and printing patterns. In view of the experimental findings, the role of the FDM processing parameters were found to play a major role in the development of components with enhanced EMI shielding efficiency.

The corrosion protection efficiency of steel painted with waterborne acrylic coatings loaded with diverse concentration of cerium oxide nanoparticles are presented in this paper. The investigation was carried out by means of Electrochemical Impedance Spectroscopy (EIS) and the salt spray test. EIS has been conducted at two experimental conditions: the intact coating condition as well as in presence of a purposely created macroscopic defect. EIS observations from the intact coatings evidenced the higher protection for the paint systems containing the ceria nanoparticles compared to that without the nanoceria, e.g. higher magnitudes for the charge transfer resistance after certain period of exposure to sodium chloride solution. In addition to that, from the evolution of the double layer capacitance on the defected coatings condition, reduced delamination rates were perceived for those containing 0.5 and 1.0 wt.% of nanoceria. Similarly, after exposure to the salt spray test a reduced delaminated area was suggested for 0.5, 1.0 and 2.0 wt.% compared to that without nanoceria. Generally, a beneficial contribution of nanoceria into an acrylic waterborne paint system on the corrosive protection of steel was found and the optimal concentration of nanoceria associated to higher corrosion protection was verified for the paint system containing 1.0 wt.%.

Corrosion protection for carbon steel by three waterborne styrene-acrylic latex coatings with different glass transition temperature (Tg) and levels of hydrophobicity has been studied by in-situ atomic force microscope (AFM) and electrochemical impedance spectroscopy (EIS) measurements in 3.0 wt% NaCl solution. The AFM images reveal the micro-and nano-structure of and pinholes in the coatings as well as their changes during exposure in the solution, whereas the EIS spectra vs. time of exposure show the barrier property, stability and degradation of the coatings. The coating with crosslinking and high level of hydrophobicity exhibited a high barrier property and long-term corrosion protection in the solution despite of some shallow pinholes. The coating without crosslinking but having high Tg and high level of hydrophobicity also displayed a high barrier property and certain stability although initial changes occur in the solution. However, for the coating without crosslinking and with low Tg and relative low level of hydrophobicity, some dissolution and open-up of defects occurred on the surface shortly after exposure and the coating lost its barrier property rapidly in the solution. The reasons for the different behaviors between the coatings are discussed with respect to the crosslinking, Tg and the hydrophobicity level of the coating. QC 20150305

Polypyrrole-coated amorphous silica short fibers (PPy-ASF) were obtained through in situ oxidative polymerization of pyrrole (Py) on the ASF surface by using ferric chloride (FeCl 3 ) as oxidant. These conducting fibers were constituted of PPy particles packed close together to form a continuous conductive layer on the ASF surface which was responsible for electrical conductivity of 0.32 S.cm −1 , similar to that found for pure PPy. The PPy-ASF were blended with polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene copolymer (SEBS) through solution casting at room temperature to form conductive rubbery (SEBS/PPy-ASF) composites. The electrical conductivity and percolation threshold of SEBS/PPy-ASF films were evaluated and also compared with PPy filled SEBS blends (SEBS/PPy) prepared under the same processing conditions. SEBS/PPy-ASF displayed lower percolation threshold and higher electrical conductivity values than those found for SEBS/PPy blends at the same conductive filler concentration. The high PPy-ASF aspect ratio (length to diameter ratio, L:D) and their good electrical conductivity allow production of conductive polymer composites at very low percolation threshold. The results obtained in this study reveal that PPy-ASF materials are promising candidates to be used as conductive filler for developing conducting polymer composites.