• Corrosion Science and Technology
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• v.10 no.6
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• pp.194-198
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• 2011

This is the first release of an interim report on the development of coating technology of Zn-Mg alloy layers on steel strip by EML-PVD (electromagnetic levitation - physical vapor deposition) process in an air-to-air type continuous PVD pilot plant. It intends to introduce a basic principle of the EML-PVD process together with the high speed PVD pilot plant built in Posco. Due to the agitation effect provided by the high frequency induction coil, simultaneous evaporation of Zn and Mg from a droplet could produce alloy coating layers with Mg content of 6% to 12% depending on the composition of the droplet inside the coil. For its superior corrosion resistance, Zn-Mg alloy coated steel would be a very promising material for automotive, electrical appliances, and construction applications.

• Transactions of Materials Processing
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• v.28 no.2
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• pp.77-82
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• 2019

Corrosion occurs well on surface of roll formed and Zn alloy subsequently electro-deposited on steel bolt under wet condition. In this study, variations in corrosion resistance were investigated through the measurement of polarization curves on steel bolts which were roll formed and subsequently coated with various types of coating methods. According to the measured polarization curve, Ni-P electroless deposits on roll formed steel increased the resistance to corrosion. The corrosion resistance of Zn alloy powder coated steel bolt was found to be better than that of Zn-Ni electro-deposited sample.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.7
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• pp.468-471
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• 2014

The effects of ZnO coating on the sensing properties of CNT:ZnO based gas sensors were studied for $H_2S$ gas. The nano ZnO sensing materials were grown by hydrothermal reaction method. CNT:ZnO was prepared by ball-mill method. The mole range of nano ZnO coating on CNT surface was from 0 to 10%. The CNT:ZnO gas sensors were fabricated by a screen printing method on alumina substrates. The structural and morphological properties of the CNT:ZnO sensing materials were investigated by XRD, EDS, SEM and TEM. The XRD patterns showed that CNT:ZnO powders with hexagonal structure were grown with (002) dominant peak. The diameter of CNT from TEM was about 28 nm.

• Journal of Ocean Engineering and Technology
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• v.19 no.5 s.66
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• pp.43-49
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• 2005

This paper is to investigate the effect of corrosion by acoustic emission method in tensile loading and the adhesiveness between substrate and coating layer. The powders used are Zn and Amdry625, respectively. They are coated on brass alloy substrate. AE signals of Zn and Amdry625 coating layer increase drastically in strain $2\%$. However, those of Zn specimen have more than those of Amdry625 specimen. When the specimens executed the corrosion test under $3.5\%$ NaCl solution for 500, 1000 hours, the salt solution penetrated into the surface of the substrate through the pores of the coating layer. As a result, corrosion production formed on the surface of the substrate. The adhesiveness between coating layers is weakened by the polarization and corrosion itself. The AE event, count, and energy of corroded coating specimens decrease, compared to specimens without corrosion. The results are summarized as follows : 1. In the tensile tests, the time that it took to start and develop the cracks and exfoliations between the surface of the substrates and the plasma spray coatings were different according to the type of plasma sprayed material, which are Zn and Amdry625. These phenomena were obvious at the strain rate 1 to $5\%$, and few available data were found after that stage. 2. The specimens with Zn coating showed the characteristics of crack, according to the changes of the tensile strength applied on the substrates while those with Amdry625 showed exfoliation as a result of low adaptation to the tensile strength. 3. The anti-corrosion specimens showed that the adhesive properties between the substrate and the plasma spray coating were strong in the order of Zn, Amdry. It showed that Corroded specimens cracked or exfoliated easily, even with the small energy, because those had a comparatively weakened adhesive property, due to corrosion. 4. Zn specimen showed no corrosion phenomena on the surface of the substrates, because they had the function of sacrifice anode however, Amdry625 specimen showed the corrosion, because it did not have that function.

• Journal of the Korean institute of surface engineering
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• v.56 no.1
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• pp.69-76
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• 2023

The effects of hairline treatment on surface blackening and thermal diffusion behaviors of Zn-Al-Mg alloy coated steel sheet were evaluated by the three-dimensional surface profiler and laser-flash technique. The metallographic observation of coating damages by hairline treatments showed that several cracks were initiated and propagated along the interface between primary Zn/eutectic phases. As the hairline processing became more severe, the crack occurrence frequency in eutectic phase of coating layer and the surface roughness increased, which had a proportional relationship with the level of blackening on the coating surface. In addition, the higher interfacial areas of the blackened coating surface, caused by the hairline process, led to an increase in thermal diffusivity and conductivity of the coated steel sheet. On the other hand, when the coating damage by hairline treatment was excessive and the steel substrate was exposed, there was little difference between the thermal diffusivity/conductivity of the untreated sample though the blackening degree was higher than that of untreated sample. This work suggests that the increase in the surface areas of the coating layer without exposure to steel substrate through hairline treatment can be one of the effective technical strategies for the development of Zn-Al-Mg alloy coated steel sheets with higher blackening level and thermal diffusivity.

• Korean Journal of Materials Research
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• v.23 no.4
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• pp.211-214
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• 2013

The effects of a Ni coating on the sensing properties of nano ZnO:Ni based gas sensors were studied for $CH_4$ and $CH_3CH_2CH_3$ gases. Nano ZnO sensing materials were prepared by the hydrothermal reaction method. The Ni coatings on the nano ZnO surface were deposited by the hydrolysis of zinc chloride with $NH_4OH$. The weight % of Ni coating on the ZnO surface ranged from 0 to 10 %. The nano ZnO:Ni gas sensors were fabricated by a screen printing method on alumina substrates. The structural and morphological properties of the nano ZnO : Ni sensing materials were investigated by XRD, EDS, and SEM. The XRD patterns showed that nano ZnO : Ni powders with a wurtzite structure were grown with (1 0 0), (0 0 2), and (1 0 1) dominant peaks. The particle size of nano ZnO powders was about 250 nm. The sensitivity of nano ZnO:Ni based sensors for 5 ppm $CH_4$ gas and $CH_3CH_2CH_3$ gas was measured at room temperature by comparing the resistance in air with that in target gases. The highest sensitivity of the ZnO:Ni sensor to $CH_4$ gas and $CH_3CH_2CH_3$ gas was observed at Ni 4 wt%. The response and recovery times of 4 wt% Ni coated ZnO:Ni gas sensors were 14 s and 15 s, respectively.

• Journal of the Korean institute of surface engineering
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• v.32 no.4
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• pp.547-554
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• 1999

The interfacial reaction, spangle and coating thickness of galvanized steel in Ni added Zn-0.18Al bath have been investigated. The size of spangle and thickness of reaction layer were observed under an optical microscope, SEM and EDS. Analysing the experimental results concerning spangle size of galvanized steel it was found that Ni addition in Zn-0.18Al bath tended to be minimized spangle size. For Zn-0.18Al bath, addition of 0.1Ni suppressed the formation of Fe-Zn intermetallic compounds but increased with Ni content above 0.1%. The coating thickness of galvanized steel was reduced with Ni addition in Zn-0.18Al bath, especially in Zn-0.18Al-0.05Ni bath. Addition of Al in Ni containing bath resulted in forming the Al-Ni intermetallic compounds such as $Al_3$Ni$_2$ and $Al_2$Ni which consist most of top precipitates.

• Journal of the Korean institute of surface engineering
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• v.34 no.6
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• pp.537-544
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• 2001

In the present study, tin-zinc alloys were coated on a cold-rolled steel sheet with variations of electrolyte concentration, additives quantity and current density employing the Hull cell and circulation cell simulator. With an addition of additives of 2m1/L, tin-zinc deposits containing 10 to 40 percent Zn revealed a good surface appearance with weak acidic electrolytes. The organic additives suppressed the Sn deposition rate and thus increased the zinc contents in tin-zinc coating layers. The zinc contents in the tin-zinc coating layers depended almost linearly on the concentrations of metal ions of tin and zinc. Temperature of the electrolyte affected the composition tin-zinc coating layer. However, the concentration of complexants revealed little effectiveness. The surface morphology of tin-zinc coating showed dense tin and zinc phases with fine equiaxed grains with the high current density.

• Journal of the Korean institute of surface engineering
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• v.32 no.1
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• pp.21-30
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• 1999

Coating adherance behavior of low carbon steels, produced by POSCO, Korea, was studied in order to study the characteristics of hot rolled galvanized iron(HGI) manufactured without pickling line and the development of its process. Galvanizing experiments were carried out in zinc pot with 0.2wt% Al after hot rolled plates with scale were reduced at $550~750^{\circ}C$ in 10~30% hydrogen gas atmosphere during 60~400seconds. The reduced plates and coated products were examined by SST, XRD, SEM and EPMA on their surfaces and cross sections. Coating layer of HGI manufactured with pickling line was composed of retained scale, Fe-Zn-Al compound, Fe-Zn compound ($\delta_1\;and\;\zeta$ Phase) and pure zinc. It was superior to HGI in coating adhesion. It seems to be due to forming of Fe-Zn-Al compound in interface of matrix and retained porous scale.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.11a
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• pp.139-140
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• 2015

Zn/HA coating on the Ti-xNb alloys after nanotube formation for dental lmplant was researched using various experimental methods. Due to g ood biocompatibility and osteoconductivity, hydroxyapatite (HA) coating s on metallic biomedical implants were widely employed in orthopedic and dental applications. To improve biocompatibilities, Zinc (Zn) plays very important roles in the bone formation and immune reg ulations. The nanotube formed Zn-HA films were characterized with X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS).