• Corrosion Science and Technology
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• 제18권6호
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• pp.292-299
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• 2019

The hull material of a high-speed ship may cause erosion damage from fluid impact. When physical erosion and electrochemical corrosion combine, erosion corrosion damage occurs. The aluminum ship is vulnerable to erosion corrosion because it can be operated at high speed. Thus, in this study, Al5052-O and Al6061-T6 aluminum alloys for the marine environment were selected as experimental materials. The erosion corrosion resistance of Al5052-O and Al6061-T6 aluminum alloys in seawater was investigated by an erosion test and potentiodynamic polarization test at the various flow rate (0 m/s, 5 m/s, 10 m/s, 15 m/s, 20 m/s). Erosion corrosion characteristics were evaluated by surface analysis, 3D analysis, SEM analysis, and the Tafel extrapolation method. The results of surface damage analysis after the erosion test showed that Al6061-T6 presented better erosion resistance than Al5052-O. The results of the potentiodynamic polarization test at the various flow rate, corrosion current density by Tafel extrapolation presented lower values of Al6061-T6 than Al5052-O. Al5052-O showed more surface damage than Al6061-T6 at all flow rates. Consequently, Al6061-T6 presented better erosion corrosion resistance than Al5052-O. The results of this study are valuable data for selecting hull material for an aluminum alloy vessel.

• 한국건설순환자원학회논문집
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• 제1권3호
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• pp.211-218
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• 2013

해양환경 조건 중 건습반복환경인 간만대는 구조물내 철근부식이 가장 빨리 일어나는 것으로 알려져 있다. 때문에 부식촉진시험 방법 중 간만대 환경을 재현한 시험방법이 가장 활발하게 진행되어왔다. 그러나 많은 연구들이 부식임계농도 추정이나 염화물침투해석에 집중되어 있는 상황이다. 본 논문에서는 건습반복조건의 환경을 재현하여 구조물내 철근부식촉진시험과 염화물 침투해석을 실시하였다. 배합에 사용된 재료의 종류를 변수로 시험을 실시하였으며, 철근부식모니터링 방법으로 갈바닉 전위측정법과 반전지전위법을 사용하여 철근부식의 유무를 판단하였다. 부식촉진시험결과 각 배합별로 부식기간이 차이가 났으며, 순서는 OPC > FA > BS > 고강도 순으로 나타났다. 부식촉진시험과 동일한 조건으로 FEM 내구성 해석 프로그램인 DuCOM, RCPT 시험을 실시하여 실험결과 값에 대한 타당성을 입증하였다.

• Advances in materials Research
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• 제13권3호
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• pp.195-202
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• 2024

Aluminum alloy is a material that is frequently used in the aerospace and transportation industries due to its high mechanical and corrosion resistance qualities. Unfortunately, aluminum alloys are prone to corrosion, limiting their application in some harsh situations such as when submerged in aqueous environments. The purpose of this study is to investigate how anodizing can increase the corrosion resistance of 6061 Aluminum alloy. The anodizing process was carried out using two different parameters which are voltage (5V, 10V, 15V) and electrolyte sulfuric acid (H₂SO₄) concentration (0.3M, 0.5M) for 1 hour. The anodized samples were performed using several analyses such as X-ray diffraction (XRD) analysis, morphology analysis, and corrosion test. From this study, it is found that the difference in anodizing parameters affects the corrosion resistance of the samples. Sample anodized at 15V, 0.5M gives the best corrosion resistance.

• Steel and Composite Structures
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• 제47권5호
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• pp.615-631
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• 2023

Steel corrosion induces structural deterioration of concrete-filled steel tubes (CFSTs), and any potential extreme action on a corroded CFST would pose a severe threat. This paper presents a comprehensive investigation on the lateral impact behaviour of CFSTs suffering from localised pitting corrosion damage. A refined finite element analysis model is developed for the simulation of locally corroded CFSTs subjected to lateral impact loads, which takes into account the strain rate effects on concrete and steel materials as well as the random nature of corrosion pits, i.e., the distribution patterns and the geometric characteristics. Full-range nonlinear analysis on the lateral impact behaviour in terms of loading and deforming time-history relations, nonlinear material stresses, composite actions, and energy dissipations are presented for CFSTs with no corrosion, uniform corrosion and pitting corrosion, respectively. Localised pitting corrosion is found to pose a more severe deterioration on the lateral impact behaviour of CFSTs due to the plastic deformation concentration, the weakened confinement and the reduction in energy absorption capacity of the steel tube. An extended parametric study is then carried out to identify the influence of the key parameters on the lateral impact behaviour of CFSTs with localised pitting corrosion. Finally, simplified design methods considering the features of pitting corrosion are proposed to predict the dynamic flexural capacity of locally pitted CFSTs subjected to lateral impact loads, and reasonable accuracy is obtained.

• 한국재난정보학회 논문집
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• 제4권1호
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• pp.138-152
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• 2008

The most important factor in the maintenance of chemical industry facilities is related with deterioration and corrosion. Leakage of hazardous materials is likely to occur because the confirmation and maintenance of bottom plates are very difficult while the bottom corrosion of the massive hazmat-storage facilities is most dangerous especially. As a result of the analysis of the corrosion locations, areas, usage condition of 287 hazmat-storage tanks on this syudy, it is concluded that the main external corrosion factors are the inflow of moisture and the materials inducing corrosion in the air such as sodium chloride and the main internal corrosion factors are corrosion react caused by stay of seawater, sulfur and moisture in hazmat for a long time without appropriate discharges. It is anticipated that the corrosion of bottom plates can be restrained effectively by establishing the proper measures for the each corrosion cause.

• Computers and Concrete
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• 제19권3호
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• pp.305-313
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• 2017

A robust finite element based reinforced concrete bridge deck corrosion initiation model is applied for time-dependent probabilistic sensitivity analysis. The model is focused on uncertainties in the governing parameters that include variation of high performance concrete (HPC) diffusion coefficients, concrete cover depth, surface chloride concentration, holidays in reinforcements, coatings and critical chloride threshold level in several steel reinforcements. The corrosion initiation risk is expressed in the form of probability over intended life span of the bridge deck. Conducted study shows the time-dependent sensitivity analysis to evaluate the significance of governing parameters on chloride ingress rate, various steel reinforcement protection and the corrosion initiation likelihood. Results from this probabilistic analysis provide better insight into the effect of input parameters variation on the estimate of the corrosion initiation risk for the design of concrete structures in harsh chloride environments.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.806-809
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• 2004

The early-age cracks have bad effects on the diffusion movement of chloride ions and oxygen. In this study, a corrosion analysis algorithm for cracked concrete is proposed to examine the influence of early-age cracks on corrosion of RC structures. For different environmental exposure conditions of RC structures, a corrosion model is combined with models for activation polarization and concentration polarization. From the finite element corrosion analysis using the proposed algorithm and the models, the effects of early-age cracks to the corrosion is simulated.

• Computers and Concrete
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• 제5권6호
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• pp.545-558
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• 2008

The corrosion of RC structures demonstrates very complicated forms of deterioration intermingled together but all pointing to a decrease in the durability of RC structures due to the corrosion of reinforcing bars. Until now, nondestructive techniques, such as half-cell potential and polarization resistance, have been widely available in the world. The former provides information on the probability of corrosion while the latter is associated with information concerning corrosion rates. Inversion by the boundary element method (IBEM) was developed for considering concrete resistivity. The applicability of the procedure was examined through a numerical analysis and electrolytic tests for RC slabs. A distribution in such concrete resistivity is relatively inhomogeneous including cracks on the surface of slabs. Regarding cracks in concrete, the relative coefficient of concrete resistance was introduced to perform its analysis. Further, the procedure will be developed to identify the corroded region visually using 3-D VRML.

• Corrosion Science and Technology
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• 제3권5호
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• pp.187-193
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• 2004

We have investigated the differences between the general corrosion and microbiologically influenced corrosion (MIC) of steels in terms of electrochemical behavior and surface phenomena. Corrosion potential of steels in the absence of SRB (sulfate-reducing bacteria) shifted to a low level and was maintained throughout the experimental period (40 days). The potential in the presence of SRB, however, shifted to a noble level after 20 days' incubation, indicating the growth of SRB biofilms on the test metal specimens and a formation of corrosion products. In addition, the color of medium inoculated with SRB changed from gray to black. The color change appeared to be caused by the formation of pyrites (FeS) as a corrosion product while no significant color change was observed in the medium without SRB inoculation. Moreover, corrosion rates of various steels tested for MIC were higher than those in the absence of SRB. This is probably because SRB were associated with the increasing corrosion rates through increasing cathodic reactions which caused reduction of sulfate to sulfide as well as formation of an oxygen concentration cell. The pitting corrosions were also observed in the SRB-inoculated medium.

• 한국표면공학회지
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• 제40권3호
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• pp.149-158
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• 2007

Of all components of MCFC(molten carbonate fuel cell), corrosion of separator is one of the most decisive factor for commercializing of MCFC. In order to provide better understanding of corrosion behavior and morphology for gas channel of separator plate, post-analysis after cell operation for 1200 hours at $650^{\circ}C$ was performed by optical microscope, SEM and EPMA. Intergranular corrosion was observed on gas channel of separator plate. Corrosion product layer was identified as Fe-oxide, Cr-oxide and Ni-oxide by EPMA, and oxide thickness was measured with a $60{\mu}m-150{\mu}m$. Also, gas channel of separator was damaged by severe intergrannular attack with post analysis in consistent with immersion test. Moreover, pitting on the channel plate was observed with a depth of $18{\sim}24{\mu}m$. The results of immersion method are well agreement with post analysis measurements.