• Steel and Composite Structures
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• v.48 no.1
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• pp.27-41
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• 2023

Under the long-term effect of corrosive environment, many cold-formed steel (CFS) structures have serious corrosion problems. Corrosion leads to the change of surface morphology and the loss of section thickness, which results in the change of instability mode and failure mechanism of CFS structure. This paper mainly investigates the elastic local buckling behavior of corroded CFS columns. The surface morphology scanning test was carried out for eight CFS columns accelerated corrosion by the outdoor periodic spray test. The thin shell finite element (FE) eigen-buckling analysis was also carried out to reveal the influence of corrosion surface characteristics, corrosion depth, corrosion location and corrosion area on the elastic local buckling behaviour of the plates with four simply supported edges. The accuracy of the proposed formulas for calculating the elastic local buckling stress of the corroded plates and columns was assessed through extensive parameter studies. The results indicated that for the plates considering corrosion surface characteristics, the maximum deformation area of local buckling was located at the plates with the minimum average section area. For the plates with localized corrosion, the main buckling shape of the plates changed from one half-wave to two half-wave with the increase in corrosion area length. The elastic local buckling stress decreased gradually with the increase in corrosion area width and length. In addition, the elastic local buckling stress decreased slowly when corrosion area thickness was relatively large, and then tends to accelerate with the reduction in corrosion area thickness. The distance from the corrosion area to the transverse and longitudinal centerline of the plate had little effect on the elastic local buckling stress. Finally, the calculation formula of the elastic local buckling stress of the corroded plates and CFS columns was proposed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.7
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• pp.16-24
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• 2019

The corrosion amounts of steel structures can be different depending on their installation condition and height. Thus, their corrosion maintenance should be considered depending on installation conditions of local structural members. In this study, an atmospheric exposure test was conducted to evaluate the corrosion amount and the corrosion rate depending on the installation condition and height of a steel water gate using monitoring steel plates and corrosion environment measuring sensors. The mean corrosion depth was evaluated using the weight loss method and the galvanic corrosion current was measured by corrosion environment measuring sensors. Local corrosion rate of local structural member in steel water gate was estimated using measured mean corrosion depths and galvanic corrosion currents. From this measurement results, the corrosion damage in horizontal member of the cross beam was highly evaluated than those of other structural member as skin plate, etc. The relative difference in the corrosion rate of a local structural member could be highly affected by local corrosion environments of steel water gate members. Therefore, an appropriate maintenance method should be considered for local corrosion damages of local structural members determined by local corrosion environments of a steel water gate.

• Steel and Composite Structures
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• v.24 no.6
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• pp.753-765
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• 2017

This paper aims to investigate the strength degradation of reinforced concrete piers wrapped with steel plates which corrode at the pier base by employing a three dimensional elasto-plastic finite element formulation. The prediction accuracy of the employed finite element analysis method is firstly verified by comparing the analytical results with test results. Then, a series of parametric studies is carried out to investigate the effects of steel plate's corrosion position along width direction, corrosion depth along plate thickness, corrosion range along width direction, and steel plate-concrete bonding degradation on the strength of the piers. It is observed that the strength degradation of the piers is closely related to steel plate's corrosion position, corrosion depth and corrosion range in the case of local corrosion on the webs. In contrast, when the base of flanges corrodes, the strength degradation of the piers is only related to steel plate's corrosion depth and corrosion range, and the influence of corrosion position on the strength degradation is very gentle. Furthermore, the strength of the piers decreases with the degradation of steel plate-concrete bonding behavior. Finally, the maximum strength of the piers obtained from numerical analysis corresponding to different bonding behavior is compared with theoretical results within an accepted error.

• Journal of Advanced Marine Engineering and Technology
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• v.27 no.6
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• pp.714-720
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• 2003

Due to the electric power shortage in summer season and regulation of freon refrigerant, the application of gas absorption refrigeration and hot water systems are considerably increasing trend. But, this system consists of condenser, heat exchanger, supply pipe and radiator etc. which are easily corroded by acidity and dissolved oxygen and gases. In result, this system occurs scale attachment and corrosion damage like pitting and crevice corrosion. In this study, electrochemical polarization test of heat exchanger tubing material (copper, aluminium brass, 30% cupronickel(30% Cu-Ni)) was carried out in 60% lithium bromide solution at $95^{\circ}C$. As a result of polarization test, corrosion behavior by impressed potential and local corrosion. such as galvanic corrosion, pitting corrosion behavior, of tubing materials was investigated. The main results obtained are as follows: (1) The effect of pitting and crevice corrosion control of 30% cupronickel in 60% LiBr solution at $95^{\circ}C$ is very excellent. (2) Dissimilar metal corrosion of 30% cupronickel coupling to aluminium bronze is the most sensitive. (3) Current density behavior of tube materials by impressed potential is high in order of copper > aluminium brass > 30% cupronickel.

• Journal of Fisheries and Marine Sciences Education
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• v.19 no.1
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• pp.84-90
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• 2007

This paper was studied on the electrochemical corrosion characteristics of weld zone for refrigerating and heating systems pipe. Austenitic stainless steel is widely applied to various fields of industry, because it is good to corrosion resistance and mechanical properties. But STS 304 is reliable to sensitization by heat cycle on welding. Therefore, in this study, electrochemical polarization test of STS 304 steel pipe manufactured by arc welding in tap water was carried out. And then polarization resistance behavior, uniform and local corrosion behaviors of base metal(BM), weld metal(WM) and heat affected zone(HAZ) for STS 304 pipe were investigated. The corrosion current density of STS 304 steel pipe is high in order of BM(153nA/cm2) < WM(614nA/cm2) < HAZ ($1.675{\mu}A/cm2$). The pitting potential of HAZ(238mV/SCE) for STS 304 is lower than BM(1206mV/SCE) and WM(369mV/SCE). Therefore, the local corrosion like pitting corrosion, galvanic corrosion and crevice corrosion of HAZ for STS 304 is more sensitive than BM and WM.

• Corrosion Science and Technology
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• v.13 no.4
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• pp.139-144
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• 2014

In corrosion-sensitive area of exsisting unpainted weathering steel bridge with closed box girder structure. there are some serious local corrosion problems because of rain water or dew water which can not be solved by conventional maintenance method. These problems must be technically controled because of the influence on the safety of bridge. This study is the first stage of developing the economic corrosion control manual for these local corrosion problems. Through the injecting experiment of tar sealant into the crevice of mock-up equipment, it was proofed that the corrosive sealant can be useful to corrosion control at crevice of corrosion sensitive area.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.988-993
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• 2004

This paper considers corrosion problems in the bolt connection of weathering steel box girder bridge using the external electric type corrosion resistance method which resisted to local corrosion in coated steel surface with contacted air. The weathering steel was created a rust itself in the passive state. but a coated box girder type was easily dew form could be made galvanic cell that accelerated corrosion. so that it was ruled by protection coat with some paint. Therefore, it needed that can be applied the external electric type corrosion resistance method in coated surface. As a result of the test of polarization amount had measured that the weathering steel was higher currents than the general steel by about $5\~10\%$. Therefore. an external electric type corrosion resistance method can be used to protect local corrosion in the coated bolt connection of weathering steel box girders effectively.

• Corrosion Science and Technology
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• v.12 no.3
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• pp.149-157
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• 2013

In corrosion-sensitive areas of exsisting unpainted weathering steel bridges with closed box girder structures. there are some serious local corrosion problems because of rain water or dew water which can not be solved by exsisting maintenance methods. These problems must be controled technically because of bad. influence on the safety of bridge. This study is the first stage of developing the economic corrosion control manual for these local corrosion problems. Through the injection of tar sealant into the crevice of mock-up equipment, it was prooved that the corrosive sealant can be useful to corrosion control at crevice of corrosion sensitive area.

• Corrosion Science and Technology
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• v.19 no.2
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• pp.66-74
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• 2020

In this paper, the author's team has carried out a comparative experimental study on the corrosion characteristics of Q235 steel commonly used in large-scale storage tanks under the specific bottom water environment found with Russian and Daqing crude oil. It was found that there is a certain degree of uniform or local corrosion on the tank floor depending on the kind of bottom water. The bottom water corrosion of Daqing crude oil is a uniform corrosion caused by carbon dioxide. While the Russian crude oil bottom water corrosion is clearly local corrosion caused by co-corrosion of carbon dioxide and hydrogen sulfide, here the corrosion rate is obviously higher than that caused by Daqing crude oil. There are two modes of storage tank inspection and maintenance that have been currently adopted by Chinese refining and chemical enterprises: a regular inspection mode and a API581-2016 risk-based detection mode. These modes have been effectively combined to form an intelligent tank inspection and maintenance mode, software tools to support this intelligent inspection and maintenance management have been developed.

• Journal of the Korean institute of surface engineering
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• v.54 no.2
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• pp.62-70
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• 2021

Al2024 aluminum alloy specimens were exposed to atmospheric conditions for maximum 24 months and analyzed by electron microscopes to characterize their corrosion behavior and oxide film characteristics. As the exposure time increased from 12 months to 24 months, the number of pitting sites per 1 mm² increased from ~100 to ~200. The uniform oxidation (or non-pitting) region of the 12-month exposure specimen showed 30~120 nm thick oxide layer, whereas the 24-month exposure specimen showed 170~200 nm thick oxide with the local oxygen penetration region up to 1 ㎛ deep. There was no local corrosion area observed in the 12-month exposure specimen except pitting. However, in the 24-month exposure specimen, local oxygen penetration region was observed beneath the uniform oxide layer and near the pitting cavity. Al2024 showed two times thicker uniform oxide layer but much shallower local oxygen penetration region than Al1050, which appears to be related to low Si concentration. Further research is needed on the effects of Mg segregation near the tip of the oxygen penetration region.