• Title/Summary/Keyword: Surface corrosion

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Microstructure and Corrosion Characteristics of Al-Si Coated PWA1426 and PWA658 Alloy (Al-Si 코팅된 PWA1426과 PWA658 합금의 미세조직과 고온부식 특성)

  • 이경구;안종천;서윤종
    • Journal of the Korean institute of surface engineering
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    • v.33 no.1
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    • pp.17-24
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    • 2000
  • The microstructures and corrosion properties of Al-Si diffusion coated PWA1426 and PWA658 alloys have been investigated. The coated layer and corrosion properties were analysed by SEM, EDS and hot corrosion test. According to the results of SEM, it is supposed that the coated layers were composed of mixed, denuded and inter-diffusion layer. The coated PWA1426 alloy improved corrosion properties, compared to the PWA658 alloy. Corrosion debris generated during hot corrosion test of PWA658 alloy are identified as NiO, $TiO_2$and $NiAl_2$$O_4$from coated layer which increase oxidation rate and decrease adhesion. The PWA1426 alloy heat treated at $1080^{\circ}C$ showed that NiAl and $Al_2$$O_3$formed on coated layer.

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Corrosion Protection Performance of Polyester-Melamine Coating with Natural Wood Fiber Using EIS Analysis

  • Shin, PyongHwa;Jo, DuHwan;Shon, MinYoung
    • Corrosion Science and Technology
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    • v.15 no.2
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    • pp.69-77
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    • 2016
  • In the present study, polyester-melamine coating systems with natural wood fiber (NWF) were prepared and the effects of NWF on the corrosion protectiveness of the polyester-melamine coating were examined using EIS analysis. From the results, higher average surface roughness was observed with increase of NWF content. Water diffusivity and water uptake into the polyester-melamine coatings with NWF were much higher than that into the pure polyester-melamine coating. The decrease in the impedance modulus |Z| was associated with the localized corrosion on carbon steel, confirming that corrosion protection of the polyester-melamine coatings with NWF well agrees with its water transport behavior.

Study on Hygrothermal Degradation and Corrosion Protection of Epoxy Coatings Cured by Different Amine Based Curing Agents

  • Shon, Min-Young;Kwon, Huck-Sang
    • Corrosion Science and Technology
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    • v.9 no.5
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    • pp.201-208
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    • 2010
  • Epoxy coatings cured by different amine based curing agents have been prepared. Atomic force microscopy (AFM) has been used to monitor the surface topology changes of epoxy coatings before and after hygrothermal cyclic test. The glass transition temperature ($T_g$) and coefficient of thermal expansion (CTE) of the epoxy coating were measured by Thermo-mechanical Analysis (TMA). The Electrochemical impedance spectroscopy (EIS) with hygrothermal cyclic test has been introduced to evaluate the corrosion protection of the epoxy coatings. In conclusion, thermal properties of epoxy coatings were in good agreement with the results of corrosion protection of epoxy coated carbon steel obtained result by EIS with hygrothermal cyclic test. The relationship between thermal properties, surface roughness changes and corrosion protection of epoxy coatings are discussed in this study.

High Temperature SO2-gas Corrosion of Fe-18%Cr-10%Ni Steels for Coal-fired Power Plant (화력발전소용 Fe-18%Cr-10%Ni 강의 고온 SO2 가스 부식)

  • Lee, Dong-Bok
    • Journal of the Korean institute of surface engineering
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    • v.40 no.5
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    • pp.219-224
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    • 2007
  • The corrosion characteristics of Fe-18Cr-10Ni steels were studied between $600^{\circ}C$ and $1000^{\circ}C$ in Ar+(0.2, 1)%$SG_2$ gas for up to 300 hr in order to employ Fe-18Cr-10Ni steels in the coal-fired power plants. The corrosion resistance of Fe-18Cr-10Ni steels was good due mainly to the high amount of Cr, which formed $Cr_2O_3$ from the initial corrosion stage. Fe in the steels corroded to mainly $Fe_2O_3$ and $Fe_3O_4$. Ni was not susceptible to corrosion under the current corrosion condition. Relatively thin, single-layered scales formed.

High Temperature Corrosion of Cr(III) Coatings in N2/0.1%H2S Gas

  • Lee, Dong Bok;Yuke, Shi
    • Journal of the Korean institute of surface engineering
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    • v.52 no.3
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    • pp.111-116
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    • 2019
  • Chromium was coated on a steel substrate by the Cr(III) electroplating method, and corroded at $500-900^{\circ}C$ for 5 h in $N_2/0.1%H_2S-mixed$ gas to study the high-temperature corrosion behavior of the Cr(III) coating in the highly corrosive $H_2S-environment$. The coating consisted of (C, O)-supersaturated, nodular chromium grains with microcracks. Corrosion was dominated by oxidation owing to thermodynamic stability of oxides compared to sulfides and nitrides. Corrosion initially led to formation of the thin $Cr_2O_3$ layer, below which (S, O)-dissolved, thin, porous region developed. As corrosion progressed, a $Fe_2Cr_2O_4$ layer formed below the $Cr_2O_3$ layer. The coating displayed relatively good corrosion resistance due to formation of the $Cr_2O_3$ scale and progressive sealing of microcracks.

Nystatin Drug as an Effective Corrosion Inhibitor for Mild Steel in Acidic Media- An Experimental and Theoretical Study

  • Mehmeti, Valbone
    • Corrosion Science and Technology
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    • v.21 no.1
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    • pp.21-31
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    • 2022
  • Potentiodynamic polarization, EIS measurements, quantum chemical calculations, and molecular dynamic simulations were used to investigate the corrosion behavior of mild steel in 0.5 M aqueous hydrochloric acid medium in the presence or absence of nystatin drug. Potentiodynamic tests suggested that this molecule could act as a mixed inhibitor due to its adsorption on the mild steel surface. The objective of this study was to exploit theoretical calculations to gain a better understanding mechanism of inhibition. Calculating the adsorption behavior of the investigated molecule on Fe (1 1 0) surface was accomplished using Monte Carlo simulation. Molecules were also investigated using Density Functional Theory (DFT), specifically PBE functional, in order to identify the link between molecular structure and corrosion inhibition behavior of the compound under investigation. Adsorption energies between nystatin and iron were estimated more accurately by utilizing Molecular Mechanics calculation with Periodic Boundary Conditions (PBC). Estimated theoretical parameters significantly assisted our understanding of the corrosion inhibition mechanism exhibited by this molecule. They were found to be in accord with experimental results.

Corrosion Inhibition Screening of 2-((6-aminopyridin-2-yl)imino)indolin-3-one: Weight Loss, Morphology, and DFT Investigations

  • Nadia Betti;Ahmed A. Al-Amiery
    • Corrosion Science and Technology
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    • v.22 no.1
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    • pp.10-20
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    • 2023
  • Because of its inexpensive cost, mild steel is frequently employed as a construction material in different industries. Unfortunately, because of its limited resistance to corrosion, a protective layer must be applied to keep it from decaying in acidic or basic environments. The presence of heteroatoms, such as nitrogen, oxygen, and pi-electrons in the Schiff base could cause effective adsorption on the mild steel surface, preventing corrosion. The weight loss method and scanning electron microscopy (SEM) were used to investigate the inhibitory effects of APIDO on mild steel in a 1 M hydrochloric acid environment. The efficiency of inhibition increased as the inhibitor concentration increased and decreased as the temperature increased. The SEM analysis confirmed that the corrosion inhibition of APIDO proceeded by the formation of an organic protective layer over the mild steel surface by the adsorption process. Simulations based on the density functional theory are used to associate inhibitory efficacy with basic molecular characteristics. The findings acquired were compatible with the experimental information provided in the research.

Europium-driven Alloy 709 corrosion in static FLiNaK molten salt at 700 ℃

  • Taiqi Yin;Amanda Leong;Jinsuo Zhang
    • Nuclear Engineering and Technology
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    • v.56 no.5
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    • pp.1738-1746
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    • 2024
  • The effect of europium-driven corrosion behavior of Alloy 709 in FLiNaK molten salt was investigated by static immersion tests at 700 ℃. It was found that the corrosion of Alloy 709 increased after the addition of EuF3, even though the standard reduction potential of Eu(III)/Eu(II) was negative than those of Fe(II)/Fe, Ni(II)/Ni and Cr (II)/Cr. The presence of Eu(III) led to deeper corrosion attack layers and more pits on the steel surface in comparison with corrosion in blank FLiNaK. However, the addition of Eu(III) seemed to have a role in reducing surface cracking that was explored in corrosion by blank FLiNaK, which depended on Eu(III) concentration.

Corrosion protection of magnesium alloys by organic coatings

  • Fazal, Basit Raza;Moon, Sungmo
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • 2016.11a
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    • pp.194.2-194.2
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    • 2016
  • Magnesium has many desirable properties of which the high strength/weight ratio makes it extremely valuable in automobile and aerospace industry. However, the high corrosion susceptibility of magnesium and its alloys has greatly limited their large scale use for various applications. Organic coating is one of the most effective ways to prevent magnesium alloys from corrosion. An organic coating is normally used in the final stage of a coating process. It can enhance corrosion resistance of magnesium and its alloys. Organic coating involves a variety of process such as painting, powder coating, cathodic electrocoating (E-painting) and the application of lacquers, enamel and varnishes.

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Effect of Fluoride Conversion Coating on the Corrosion Resistance and Adhesion of E-painted AZ31 Magnesium Alloy

  • Fazal, Basit Raza;Moon, Sungmo
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • 2016.11a
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    • pp.124.2-124.2
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    • 2016
  • Corrosion resistance and adhesion of electro-paint (E-paint) with fluoride conversion coating (FCC) on AZ31 Mg alloy were studied. Corrosion resistance and adhesion were studied as a function of FCC-treatment time and concentration of FCC-bath. Aqueous hydrogen fluoride (HF) solutions, with concentrations ranging from 0.5 M to 5 M, were used to form FCC on chemically polished AZ31 Mg alloy samples for six different times; 10, 30, 60, 90, 120, and 180s. The results from salt spray test (SST) showed that corrosion resistance of E-paint appeared to decrease with increasing FCC treatment times in low concentration FCC baths. The number of blisters formed on the FCC-treated samples increased with increasing FCC treatment time of more than 1 min in low concentration (0.5 M to 1 M) solutions. On the other hand, samples treated in the 5 M HF solution for 120s showed no delamination or blistering even after 1200h of SST.

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