• Title/Summary/Keyword: critical corrosion

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Corrosion Resistance of Fe-Mn-Si-Ni-Cr-TiC Shape Memory Alloy for Reinforcement of Concrete (콘크리트 보강재용 Fe-Mn-Si-Ni-Cr-TiC계 형상기억합금의 내식성)

  • Joo, Jaehoon;Lee, Hyunjoon;Kim, Dohyoung;Lee, Wookjin;Lee, Junghoon
    • Journal of the Korean institute of surface engineering
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    • v.52 no.6
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    • pp.364-370
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    • 2019
  • Fe-Mn-Si-Ni-Cr-TiC alloys have a shape memory property, recovering initial shape by heating. With an aim to improve a durability and stability of building and infrastructure, this Fe-based shape memory alloy (FSMA) can be employed to reinforce concrete structure with creation of compressive residual stress. In this work, corrosion resistance of FSMA was compared with general rebar and S400 carbon steel to evaluate the stability in concrete environment. Potentiodynamic polarization test in de-ionized water, tap-water and 3.5 wt.% NaCl solution with variations of pH was used to compare the corrosion resistance. FSMA shows better corrosion resistance than rebar and S400 in tested solutions. However, Cl-containing solution is critical to significantly reduce the corrosion resistance of FSMA. Therefore, though FSMA can be a promising candidate to replace the rebar and S400 for the reinforcement of concrete structure, serious cautions are required in marine environments.

Prediction of shear strength and drift capacity of corroded reinforced concrete structural shear walls

  • Yang, Zhihong;Li, Bing
    • Structural Engineering and Mechanics
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    • v.83 no.2
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    • pp.245-257
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    • 2022
  • As the main lateral load resisting system in high-rise reinforced concrete structures, the mechanical performance of shear wall has a significant impact on the structure, especially for high-rise buildings. Steel corrosion has been recognized as an important factor affecting the mechanical performance and durability of the reinforced concrete structures. To investigate the effect on the seismic behaviour of corroded reinforced concrete shear wall induced by corrosion, analytical investigations and simulations were done to observe the effect of corrosion on the ultimate seismic capacity and drift capacity of shear walls. To ensure the accuracy of the simulation software, several validations were made using both non-corroded and corroded reinforced concrete shear walls based on some test results in previous literature. Thereafter, a parametric study, including 200 FE models, was done to study the influence of some critical parameters on corroded structural shear walls with boundary element. These parameters include corrosion levels, axial force ratio, aspect ratio, and concrete compressive strength. The results obtained would then be used to propose equations to predict the seismic resistance and drift capacity of shear walls with various corrosion levels.

A methodology to evaluate corroded RC structures using a probabilistic damage approach

  • Coelho, Karolinne O.;Leonel, Edson D.;Florez-Lopez, Julio
    • Computers and Concrete
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    • v.29 no.1
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    • pp.1-14
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    • 2022
  • Several aspects influence corrosive processes in reinforced concrete (RC) structures such as environmental conditions, structural geometry and mechanical properties. Since these aspects present large randomnesses, probabilistic models allow a more accurate description of the corrosive phenomena. Besides, the definition of limit states in the reliability assessment requires a proper mechanical model. In this context, this study proposes a straightforward methodology for the mechanical-probabilistic modelling of RC structures subjected to reinforcements' corrosion. An improved damage approach is proposed to define the limit states for the probabilistic modelling, considering three main degradation phenomena: concrete cracking, rebar yielding and rebar corrosion caused either by chloride or carbonation mechanisms. The stochastic analysis is evaluated by the Monte Carlo simulation method due to the computational efficiency of the Lumped Damage Model for Corrosion (LDMC). The proposed mechanical-probabilistic methodology is implemented in a computational framework and applied to the analysis of a simply supported RC beam and a 2D RC frame. Curves illustrate the probability of failure evolution over a service life of 50 years. Moreover, the proposed model allows drawing the probability of failure map and then identifying the critical failure path for progressive collapse analysis. Collapse path changes caused by the corrosion phenomena are observed.

Localized Corrosion Resistance and Microstructural Changes in UNS N07718 Alloy After Solution Heat Treatment

  • Yoon-Hwa Lee;Jun-Seob Lee;Soon il Kwon;Jungho Shin;Je-Hyun Lee
    • Corrosion Science and Technology
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    • v.23 no.2
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    • pp.166-178
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    • 2024
  • The localized corrosion resistance of UNS N07718 alloy was investigated after solution heat treatment. When the alloy was heat-treated at 1050 ℃ for 2.5 hours, it experienced an increase in average grain diameter, a reduction in grain boundary area, and the dissolution of delta phases along grain boundaries. Additionally, primary metallic nitrides (MN) and metallic carbides (MC), enriched with either Ti or Nb, were identified and exhibited a random distribution within the microstructures. Despite the solution heat treatment, the composition, diameter, and abundance of MNs and MCs remained relatively consistent. The critical pitting temperature (CPT), as determined by the ASTM G48-C immersion test, revealed similar values of 45 ℃ for both treated and untreated alloys. However, a decrease in maximum pit depth and corrosion rate was observed after the solution heat treatment. The microstructural changes that occurred during the heat treatment and their potential implications were discussed to understand the influence of the solution heat treatment.

Development of Automatic Ultrasonic Testing Equipment for Pressure-Retaining Studs and Bolts in Nuclear Power Plant (원자력 발전소 STUD BOLT의 자동초음파 주사장치 개발)

  • Suh, D.M.;Park, M.H.;Hong, S.S.
    • Journal of the Korean Society for Nondestructive Testing
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    • v.9 no.1
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    • pp.106-110
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    • 1989
  • Bolting degradation problems in primary coolant pressure boundary applications have become a major concern in the nuclear industry. In the bolts concerned, the failure mechanism was either corrosion wastage(loss of bolt diameter) or stress-corrosion cracking.(3) Here the manual ultrasonic testing of RPV(Reactor Pressure Vessel) and RCP(Reactor Coolant Pump) stud has been performed. But it is difficult to detect indications because examiner can not exactly control the rotation angle and can not distinguish the indication from signals of bolt. In many cases, the critical sizes of damage depth are very small(1-2 mm order). At critical size, the crack tends to propagatecompletly through the bolt under stress, Resulting in total fracture.(3) Automatic stud scanner for studs(bolts) was developed because the precise measurement of bolt diameter is required in this circumstance. By use of this scanner, the rotation angle of probe was exactly controlled and the exposure time of radiations was reduced.

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Moist Corrosion and Surface Protection of YBCO HTS

  • Lim, Byong-Jae;Soh, Dea-Wha;Fan, Zhanguo
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2002.11a
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    • pp.256-259
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    • 2002
  • The critical currents of sintered $YBa_{2}Cu_{3}O_{6.5+\delta}$ were measured as the variables with the corrosive time in the humid air. The corrosive process was studied by means of the current changes. Ag coating on the textured YBCO and polytetrafluoroethylene (PTFE) coating on the sintered YBCO were prepared. The critical current densities of different YBCO samples with and without coatings were compared. Both Ag coating and PTFE coating can well protect YBCO from moisture and $CO_{2}$.

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Reliability-Based Performance Assessment and Prediction of Tendon Corrosion in K-UHPC Bridges (K-UHPC 교량의 긴장재 부식에 관한 신뢰성 기반 성능 평가 및 예측)

  • Kwon, Kihyon;Park, Sung Yong;Cho, Keunhee;Kim, Sung Tae;Park, Jong Beom;Kim, Byung Suk
    • Journal of the Korean Society of Safety
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    • v.31 no.3
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    • pp.75-81
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    • 2016
  • Tendon corrosion reliability in KICT-ultra high performance concrete (K-UHPC) bridges is assessed and predicted considering uncertainties in flexural bending capacity and corrosion occurrence. In post-tensioning bridge systems, corrosion is a one of most critical failure mechanisms due to strength reduction by it. During the entire service life, those bridges may experience lifetime corrosion deterioration initiated and propagated in tendons which are embedded not only in normal concrete but also in K-UHPC. For this reason, the time-variant corrosion performance has to be assessed. In the absence of in-depth researches associated with K-UHPC tendon corrosion, a reliability-based prediction model is developed to evaluate lifetime corrosion performance of tendon in K-UHPC bridges. In 2015, KICT built a K-UHPC pilot bridge at 168/5~168/6 milestone on Yangon-Mandalay Expressway in Myanmar, by using locally produced tendons which post-tensioned in longitudinal and lateral ways of K-UHPC girders. For an illustrative purpose, this K-UHPC bridge is used to identify the time-variant corrosion performance.

Prediction of tensile strength degradation of corroded steel based on in-situ pitting evolution

  • Yun Zhao;Qi Guo;Zizhong Zhao;Xian Wu;Ying Xing
    • Steel and Composite Structures
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    • v.46 no.3
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    • pp.385-401
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    • 2023
  • Steel is becoming increasingly popular due to its high strength, excellent ductility, great assembly performance, and recyclability. In reality, steel structures serving for a long time in atmospheric, industrial, and marine environments inevitably suffer from corrosion, which significantly decreases the durability and the service life with the exposure time. For the mechanical properties of corroded steel, experimental studies are mainly conducted. The existing numerical analyses only evaluate the mechanical properties based on corroded morphology at the isolated time-in-point, ignoring that this morphology varies continuously with corrosion time. To solve this problem, the relationships between pit depth expectation, standard deviation, and corrosion time are initially constructed based on a large amount of wet-dry cyclic accelerated test data. Successively, based on that, an in-situ pitting evolution method for evaluating the residual tensile strength of corroded steel is proposed. To verify the method, 20 repeated simulations of mass loss rates and mechanical properties are adopted against the test results. Then, numerical analyses are conducted on 135 models of corrosion pits with different aspect ratios and uneven corrosion degree on two corroded surfaces. Results show that the power function with exponents of 1.483 and 1.091 can well describe the increase in pit depth expectation and standard deviation with corrosion time, respectively. The effect of the commonly used pit aspect ratios of 0.10-0.25 on yield strength and ultimate strength is negligible. Besides, pit number ratio α equating to 0.6 is the critical value for the strength degradation. When α is less than 0.6, the pit number increases with α, accelerating the degradation of strength. Otherwise, the strength degradation is weakened. In addition, a power function model is adopted to characterize the degradation of yield strength and ultimate strength with corrosion time, which is revised by initial steel plate thickness.

Application of the Plasma Etching technique to Fabricating a Concave-type Pt Electrode Capacitor

  • Kim, Hyoun Woo;Hwang, Woon Suk
    • Corrosion Science and Technology
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    • v.2 no.5
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    • pp.243-246
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    • 2003
  • We have used a plasma etching method in order to develop a concave-type Pt electrode capacitor to overcome the limitation of conventional stack-type capacitor in a small critical-dimension (CD) pattern. We have deposited Pt layer on the concave-type structure made by patterning of $SiO_2$ and subsequently we separated the adjacent nodes by etch-back process with photoresist (PR) as a protecting layer.

Ultrasonic Detection of Small Crack in Studs[Bolts] by Time Difference of Thread Signals(TDTS) (초음파진행 시간차에 의한 STUD[BOLT] 나사산의 미세한 결함검출)

  • Suh, D.M.;Park, D.Y.;Kim, C.K.
    • Journal of the Korean Society for Nondestructive Testing
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    • v.10 no.1
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    • pp.38-46
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    • 1990
  • It is difficult to detect such flaws as stress - corrosion cracking or corrosion wastage(loss of bolt diameter) in the threads. In many cases the critical size of a flaw is very small(1-2 mm order). This paper describes how it is possible to discriminate small flaw indications in threads using the time difference or thread signals(TDTS) by a signal-conditioning technique.

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