Degradation of Coatings under Atmospheric Tropical Conditions

Hang, To Thi Xuan,Vu, Pham Gia,Oanh, Vu Ke,Truc, Trinh Anh,Kodama, Toshiaki,Tanabe, Hiroyuki,Taki, Tohru,Nagai, Masanori 한국부식방식학회 2003 Corrosion Science and Technology Vol.2 No.5

The weather resistance of five coatings systems based on alkyd, chlorinated rubber, epoxy, polyurethane and fluoropolymer were studied by natural exposure test and accelerated test. The coatings were exposed at Hanoi station with urban industry atmosphere and at Baichay stationwith marine atmosphere. The degradation of coatings was evaluated by gloss measurement and surface analysis by scanning clcctronic microscopy. The results obtained show that among coatings tested the gloss of polyurethane and tluoropolymer coatings remained highly and those of alkyd chlorinated rubber and epoxy coatings were very low afler two years of atmospheric exposure. Under accelerating conditions the gloss of fluoropolymer coatings remained highly after 80 cycles of testing. By compxison with accelerating test in UV-condensation chamber the conditions at atmospheric stations are more aggressive.

Inhibitory Effect of Benzoate-intercalated Hydrotalcite with Ce³⁺-loaded clay on Carbon Steel

( Thuy Duong Nguyen ),( Thu Thuy Pham ),( Anh Son Nguyen ),( Ke Oanh Vu ),( Gia Vu Pham ),( To Thi Xuan Hang ) 한국부식방식학회 2023 Corrosion Science and Technology Vol.22 No.1

This work studied the inhibitory effect of the combination of benzoate-intercalated hydrotalcite (HT-BZ) and Ce³⁺-loaded clay (Clay-Ce) on carbon steel (CS). HT-BZ was prepared by the co-precipitation method and Clay-Ce was fabricated by a cation exchange reaction. HT-BZ and Clay-Ce were assessed by scanning electron microscopy (SEM) and X-ray diffraction (XRD) coupled with zeta potential measurement. Electrochemical measurements coupled with scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX) were used for studying the inhibitory action of the mixture of HT-BZ and Clay-Ce on steel electrodes immersed in 0.1 M NaCl. For comparison, the inhibitory effect of HT-BZ or Clay-Ce alone was also evaluated. The results showed that HT-BZ combined with Clay-Ce provided synergistic inhibition of the CS substrate. The mixture of 0.5 g/L HT-BZ + 0.5 g/L Clay-Ce provided 93.5% inhibition efficiency. The protective mechanism of the HT-BZ + Clay-Ce mixture consisted of the reaction of released BZ and Ce³⁺ and the deposition of HT-BZ and Clay-Ce structures on the CS substrate.

Effect of Zn/Al Cation Ratio on Corrosion Inhibition Capabilities of Hydrotalcites Containing Benzoate Against Carbon Steel

Thuy Duong Nguyen,To Thi Xuan Hang,Thu Thuy Pham,Anh Son Nguyen,Thu Thuy Thai,Gia Vu Pham,Ngoc Bach Ta 한국부식방식학회 2022 Corrosion Science and Technology Vol.21 No.6

Corrosion inhibitors based on Zn-Al hydrotalcites containing benzoate (ZnAlHB) with different molar ratios of Zn/Al were prepared with a co-precipitation process. Compositions and structures of the resulting hydrotalcites were studied with suitable spectroscopic methods such as inductively coupled plasma mass spectrometry (ICP-MS), ultraviolet-visible spectrophotometry (UV-Vis), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and surface zeta potential measurements, respectively. Results of physico-chemical studies showed that crystallite sizes, compositions of products, and surface electrical properties were significantly changed when the molar ratio of Zn/Al was increased. The release of benzoate from hydrotalcites also differed slightly among samples. Anticorrosion abilities of hydrotalcites intercalated with benzoate at a concentration of 3 g/L on carbon steel were analyzed using electrochemical impedance spectroscopy (EIS), polarization curve, energy-dispersive X-ray spectroscopy (EDX), and SEM. Corrosion inhibition abilities of benzoate modified hydrotalcites in 0.1 M NaCl showed an upward trend with increasing Zn/Al ratio. The reason for the dependence of corrosion resistance on the Zn/Al ratio was discussed, including changes in the microstructure of hydrotalcites such as crystal size, density, uniformity, and formation of ZnO.

Comparative study on the performance of microwave-assisted plasma DRM in nitrogen and argon atmospheres at a low microwave power

Nabil Majd Alawi,Jaka Sunarso,Gia Hung Pham,Ahmed Barifcani,Minh Hoang Nguyen,Shaomin Liu 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.85 No.-

Dry reforming of methane (DRM) is an attractive route to convert CH4 and CO2 into syngas (a mixture ofCO and H2). In this work, the performance of microwave-assisted DRM at atmospheric pressure (interms of CH4 and CO2 conversions, H2 and CO selectivities, H2 and CO yields, and H2 to CO ratio) isstudied as functions of additive gasflow rate, microwave power, CO2 to CH4 inlet supply ratio, andreaction time. Two additive gases were used, i.e., nitrogen and argon. Microwave-assisted DRMexperiments in both gases show identical trend of conversions, selectivities, yields, and product ratio. DRM performances in both additive gases atmosphere were stable for up to 8 h. Under the sameoperating conditions, using Ar as an additive gas, however, led to higher H2 and CO selectivities andyields and thus, higher H2 to CO ratio relative to using N2 as an additive gas. Maximum CH4 and CO2conversions of 79.35% and 44.82%, H2 and CO selectivities of 50.12% and 58.42%, H2 and CO yields of39.77% and 32.89%, and H2 to CO ratio of 0.86 were obtained at 700 W and N2, CO2, and CH4 flow rates of1.5, 0.4, and 0.2 L min 1, respectively.

Size-tailored microwave absorption and reaction activity of Co3O4 nanocatalysts

Hoang M. Nguyen,Chi M. Phan,Gia Hung Pham,Yusuke Asakuma,Robert Vagnoni,Shaomin Liu 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.94 No.-

Microwave (MW)-assisted heterogeneous catalytic chemical reactions have opened advanced routinesover the conventional methodology. MW absorption ability of catalyst governed by its particle size is theforemost important factor to be considered before designing catalysts for such MW-based chemistry. Despite considerable interest in applying metallic-based catalysts for MW-assisted reactions, theinfluences of particle size on catalyst’s MW absorption ability and its resultant activity remain elusive. Here, we report an effective approach to tailor the MW absorption ability of Co3O4 catalyst via controllingits particle size during the crystal growth. A developed theoretical model verified that a capping agentcould regulate Co3O4 particle size effectively. For the unsupported Co3O4 catalysts, smaller particle sizepossessed higher MW absorption capacity and thereby delivered higher activity for MW-assisted bireformingof methane. High conversion of 63% CH4 and a syngas ratio (H2/CO) of 2.2 was achieved withthe smallest Co3O4 particles, at 20 nm. In contrast, the supported Co3O4 samples required larger particlesto ensure adequate exposure to the incident MW, which is partially covered by MW-inert support. Theresults disclose that by tailoring particles size appropriately, metallic-based catalysts can be optimisedfor MW-based chemical reactions.

The Influence of Hydrotalcite Intercalated with Benzoate on UV Stability of Acrylic Coating

Thuy Duong Nguyen,Anh Son Nguyen,Thu Thuy Thai,Gia Vu Pham,Thi Xuan Hang To,Marie-Georges Olivier 한국부식방식학회 2020 Corrosion Science and Technology Vol.19 No.1

It is important to realize that benzoate was intercalated into hydrotalcite (HTC-Bz) by the co-precipitationmethod. In this case, acrylic coating with 0.5 wt% HTC-Bz was deposited on carbon steel using the spincoating method. Next, the HTC-Bz structure was characterized by Field emission scanning electron microscopy(FESEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). In fact, an ultravioletvision spectroscopy (UV-Vis) was used to determine the benzoate content in HTC-Bz, and the UV absorptionability of HTC-Bz. Using electrochemical techniques, water contact angle measurement, and thermal-gravimetricanalysis, we compared the protective properties before and after QUV test, hydrophobicity and the thermalstability of acrylic coating containing HTC-Bz. The obtained results showed that HTC-Bz with a plate-likestructure was successfully synthesized; benzoate was intercalated into the interlayer of hydrotalcite witha concentration of 28 wt%. Additionally, it was noted that HTC-Bz has an UV absorption peak at 225nm. In conclusion, the addition of HTC-Bz enhanced the UV stability, hydrophobicity and the thermal stabilityof acrylic coating.

Synthesis and Characterization of Hydrotalcite/Graphene Oxide Containing Benzoate for Corrosion Protection of Carbon Steel

( Thuy Duong Nguyen ),( Boi An Tran ),( Ke Oanh Vu ),( Anh Son Nguyen ),( Anh Truc Trinh ),( Gia Vu Pham ),( Thi Xuan Hang To ),( Thanh Thao Phan ) 한국부식방식학회(구 한국부식학회) 2020 Corrosion Science and Technology Vol.19 No.2

This work examined the corrosion protection performance of benzoate loaded hydrotalcite/graphene oxide (HT/GO-BZ) for carbon steel. HT/GO-BZ was fabricated by the co-precipitation method and characterized by infrared spectroscopy, X-ray diffraction, and scanning electronic microscopy. The corrosion inhibition action of HT/GO-BZ on carbon steel in 0.1 M NaCl solution was evaluated by electrochemical measurements. The benzoate content in HT/GO-BZ was determined by UV-Vis spectroscopy. Subsequently, the effect of HT/GO-BZ on the corrosion resistance of the water-based epoxy coating was investigated by the salt spray test. The obtained results demonstrated the intercalation of benzoate and GO in the hydrotalcite structure. The benzoate content in HT/GO-BZ was about 16%. The polarization curves of the carbon steel electrode revealed anodic corrosion inhibition activity of HT/GO-BZ and the inhibition efficiency was about 95.2% at a concentration of 3g/L. The GO present in HT/GO-BZ enhanced the inhibition effect of HT-BZ. The presence of HT/GO-BZ improved the corrosion resistance of the waterborne epoxy coating.

Investigation of Extruded Endwall on Heat Transfer Characteristics of Channel with Staggering Pin-fins

Van-Hoang Tran,Thanh-Huan Nguyen,Frédéric Plourde,Khanh-Duy Cong Do,Duy-Hung Chung,Cong-Truong Dinh,Gia-Diem Pham 한국유체기계학회 2023 International journal of fluid machinery and syste Vol.16 No.2

In order to increase turbine efficiency while retaining structural integrity, modern jet engines need an effective cooling system. Pin-fin arrays play a significant role in the internal cooling system of the turbine blade. In examining the efficacy of cooling techniques using pin-fins, the other papers focus on pin-fin configurations. In contrast, the current study is a step toward optimizing cooling cascade endwalls for better maneuvering and reservation of vortices, which leads to more considerable heat transfer near the endwalls. This study examines the flow field and heat transfer of roughed endwall in the pin-fin channel, including varieties with flat endwall and extruded endwall. The heat transfer of the channel and pressure drop properties of the extruded endwall case are quantitatively assessed to contrast with those of the flat endwalls scenario for an intake Reynolds number range of 7400 to 36000. The leading and trailing surfaces of the channel are divided into five streamwise regions to understand better how well the pin-fins and endwalls transmit heat. The results show that the new endwall construction significantly increases the high heat transfer zones around the pin-fins compared to the flat endwall scenario. In the meantime, the heat transfer of the channel to the pin-fins is enhanced by the modified endwall configuration. The redesigned endwall outperformed the basic case regarding the HTEI, rising by 15.9%. It is found that the friction factor of the new design is increased due to the narrowing channel. However, due to their much higher heat transfer capacity, the HTEI of extruded endwall is up to 41.5% higher than the HTEI of the channel with flat endwalls. These results demonstrate that the heat transfer properties of pin-fins can be significantly improved by optimizing endwall design.