Institute for Tropical Technology

Cau Giay, Vietnam

Institute for Tropical Technology

Cau Giay, Vietnam
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Nguyen A.S.,ENSIACET | Nguyen A.S.,Institute for Tropical Technology | Causse N.,ENSIACET | Musiani M.,CNR Institute of Neuroscience | And 4 more authors.
Progress in Organic Coatings | Year: 2017

Electrochemical impedance spectroscopy (EIS) and gravimetric measurements on two water-based coatings, containing either SrCrO4 or a mixture of Cr(VI)-free pigments and deposited on 2024 aluminium alloy, were performed to follow the water uptake in a 0.5 M NaCl solution as a function of exposure time. To account for the observed non-ideal capacitive behaviour, the coating capacitance and dielectric constant values were extracted from the EIS data in two ways: (i) by using a complex-capacitance representation and (ii) by fitting to the EIS data a model that assumed an exponential distribution of coating resistivity. The agreement of values obtained by these independent methods served to validate the model used to account for the observed pseudo constant-phase-element (CPE) behaviour of the coatings. The water uptake calculated from dielectric constant values, employing a linear combination formula, was in good agreement with that directly measured by gravimetry, using supported-films. © 2017 Elsevier B.V.


Nguyen T.H.,Hanoi National University of Education | Nguyen T.A.,Institute for Tropical Technology | Nguyen T.V.,Institute for Tropical Technology | Le V.K.,Hanoi National University of Education | And 3 more authors.
International Journal of Corrosion | Year: 2015

The electrical rehabilitation treatments of repair mortar were performed with tetrabutylammonium bromide salt (TBAB) at an electrical current density of 5 A/m2, using two electrolytes (0.1 M NaOH and 0.1 M Na3BO3 solutions), and for two time periods (1 and 4 weeks), respectively. The average organic cation-based inhibitor's concentration in cement mortars before and after this treatment was quantified using the UV-Vis spectroscopy. The experimental results reveal that the EICI treatment with 0.1 M Na3BO3 was more effective in injecting the inhibitor and in improving the chloride penetration resistance and compressive strength of the mortar, relative to using 0.1 M NaOH as electrolyte. In this case, after the 4-week EICI treatment, [TBA+] contents were 2.3 % and 2.4% by mass of cement mortar for uncontaminated and salt-contaminated mortars, respectively. After the 4-week EICI treatment, the apparent diffusion coefficients of chloride anion in cement mortar were decreased by 40% from 1.52 × 10-10 m2/s. The EICI treatment was able to halt the chloride-induced corrosion of the steel rebar by promoting its passivation. The 2-week EICI treatment using sodium hydroxide and sodium borate solutions decreased the corrosion current density of the rebar by 77.8% and 78.5%, respectively, approximately two months after the treatment. © 2015 The Huyen Nguyen et al.


Hang T.T.X.,Institute for Tropical Technology | Truc T.A.,Institute for Tropical Technology | Olivier M.-G.,University of Mons | Vandermiers C.,University of Mons | And 2 more authors.
Progress in Organic Coatings | Year: 2010

This work is an extension of studies into the mechanisms of corrosion protection of mild steel by an epoxy resin containing organically modified clay (Hang et al. [1]; Truc et al. [2]). In a previous study (Truc et al. [2]), it was shown that indole-3 butyric acid (IBA)-modified clay improved the corrosion performance of epoxy. In the present study, it was shown that the IBA is an anodic inhibitor and its efficiency was about 93%. Exfoliation and dispersion of the IBA-modified clay in the epoxy coating were checked by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The improvement of the corrosion performance of the epoxy coating containing IBA-modified clay by comparison with pure epoxy coating was confirmed for a low film thickness (10 μm). Local electrochemical impedance measurements performed on scratched samples revealed the inhibitive action of IBA at the carbon steel/coating interface. It was shown that the inhibitor release from the IBA-modified clay was favoured for high pH values. Thus, in neutral media, the corrosion process which induces a local increase of pH will increase the self-healing performance. © 2010 Elsevier B.V.


Nguyen T.A.,Institute for Tropical Technology | Nguyen H.,Hanoi National University of Education | Nguyen T.V.,Institute for Tropical Technology | Thai H.,Institute for Tropical Technology | Shi X.,Washington State University
Journal of Nanoscience and Nanotechnology | Year: 2016

Epoxy coatings incorporated with several nanoparticles, such as nano-SiO2, nano-Fe2O3, nanoclay and nano-TiO2, were synthesized on the surface of steel substrates by solvent sonication and room-temperature curing of fully mixed epoxy slurry. The morphologies of the epoxy nanocomposite coating were investigated using transmission electron microscopy (TEM). The effects of incorporating various nanoparticles on the thermal properties of epoxy-coated steel were investigated using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The effect of nanoparticles on the mechanical properties of the epoxy was investigated using adhesion strength and ball impact tests. TEM results showed that the nanoparticles (especially nano-TiO2) were dispersed homogeneously into the entire volume of the resin. DSC and TGA studies revealed that nanoparticles resulted in improved cross-link density, as evidenced by the increased glass transition temperature. Nano-TiO2 increased the Tg value of the epoxy coating from 58 °C up to 170 °C. Epoxy nanocomposites modified by nano-ZnO possessed the best thermal stability. The impact test results showed that the incorporation of nanoparticles (especially nano-TiO2) can improve the impact strength the epoxy coating significantly. The adhesion strength test data show that the presence of nano-Fe2O3 particles improved the adhesion of the epoxy coatings. © Copyright 2016 American Scientific Publishers. All rights reserved.


Trinh A.T.,Institute for Tropical Technology | Nguyen T.T.,Institute for Tropical Technology | Thai T.T.,Institute for Tropical Technology | To T.X.H.,Institute for Tropical Technology | And 4 more authors.
Journal of Coatings Technology Research | Year: 2016

In this study, synthesized magnetite (Fe3O4) nanoparticles were treated with a corrosion inhibitor, indole-3 butyric acid (IBA) and incorporated in an epoxy-polyamide coating. The coating was applied on a carbon steel substrate. For comparison, coatings without particles or with nontreated Fe3O4 particles were also prepared. The IBA-modified nanomagnetite (IBA–Fe3O4) was characterized by infrared spectroscopy and Zeta potential measurements. The inhibitive action of IBA was shown by electrochemical measurements (polarization curves) performed for a bare carbon steel in 0.1 M NaCl solution containing Fe3O4 or IBA–Fe3O4 nanoparticles. Adherence and anticorrosion properties of the epoxy-based coatings containing Fe3O4 or IBA–Fe3O4 were compared to those of the pure epoxy-polyamide resin by dry and wet adherence measurements and by salt spray test. The results showed significant improvement of the film adherence and higher corrosion protection of the carbon steel in the presence of IBA–Fe3O4. It was concluded that the IBA effect was restricted to the metal/coating interface. © 2016, American Coatings Association.


Nguyen T.V.,Institute for Tropical Technology | Nguyen Tri P.,University of Montréal | Nguyen T.D.,Institute for Tropical Technology | El Aidani R.,ETS | And 2 more authors.
Polymer Degradation and Stability | Year: 2016

In this study, the degradation of a water-borne acrylic coating and the influence of rutile-TiO2 (R-TiO2) nanoparticles and a hindered amine light stabilizer (HALS) on its photo-stability in accelerated aging environment has been quantitatively studied by monitoring the chemical modifications occurring upon aging conditions. By using non-destructive analytical methods, like IR and UV-visible spectroscopy, 3D laser microscopy, SEM observations and weight loss measurements, it was possible to follow continuously the formation of photo-oxidative products and the loss of the binder functional groups on a sample undergoing accelerated aging. For the first time, numerous dark spots, randomly dispersed on the whole surface of the sample upon UV/condensation exposure are successfully observed and explained by using a novel technique 3D laser microscopy. Our findings also confirm that HALS greatly improved photo-stability to the coating thank to its free radical and hydrogen peroxide scavenging capacity. This work provides some useful information for a better understanding of the degradation behavior of water-borne acrylic coating under accelerated aging conditions. © 2016 Elsevier Ltd. All rights reserved.

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