• Journal of Korean Society of Steel Construction
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• v.28 no.4
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• pp.213-222
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• 2016

For a steel structure with long service period, structural performance can be changed or decreased by corrosion damage occurred under severe corrosion environment condition. In this study, to examine compressive strength and behavior of circular steel member depending on corrosion damage, compressive loading tests were conducted using circular steel member with artificial corrosion damage which was applied by mechanical process and hand drill. From test results, local corrosion area and pattern is related to their structural performance. Their lcoal bucklings were occurred near artificially sectional damaged part. Reduction in compressive strength of circular steel member was also suggested according to their corroded part and damage.

• Corrosion Science and Technology
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• v.14 no.5
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• pp.239-246
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• 2015

Stainless steel is generally known to have characteristics of excellent corrosion resistance and durability, but in a marine environment it can suffer from localized corrosion due to the breakdown of passivity film due to chloride ion in seawater. Furthermore, the damage behaviors are sped up under a cavitation environment because of complex damage from electrochemical corrosion and cavitation-erosion. In this study the characteristics of electrochemical corrosion and cavitation erosion behavior were evaluated on 16.7Cr-10Ni-2Mo stainless steel under a cavitation environment in natural seawater. The electrochemical experiments have been conducted at both static conditions and dynamic conditions inducing cavitation with different current density parameters. The surface morphology and damage behaviors were compared after the experiment. After the cavitation test with time variables morphological examinations on damaged specimens were analyzed by using a scanning electron microscope and a 3D microscope. the galvanostatic experiment gave a cleaner surface morphology presented with less damage depth at high current density regions. It is due to the effect of water cavitation peening under the cavitation condition. In the cavitation experiment, with amplitude of $30{\mu}m$ and seawater temperature of $25^{\circ}C$, weight loss and cavitation-erosion damage depth were dramatically increased after 5 hours inducing cavitation.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.33 no.3
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• pp.202-208
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• 1997

The component materials threatened by cavitation include ship propellers as well as turbine runners, pump impellers, pipe lines and radiators. Today it is known that cavitation damage takes place on many other components including on the coding water side of the cylinder liners of diesel engines. Cavitation erosion - corrosion implies damage to materials due to the shock pressure or shock wave that results when bubbles form and collapse at a metal surface within a liquid. To suppress cavitation erosion as well as cavitation erosion - corrosion to hydraulic equipment, innovations such as the improvement in the geometric design of the equipment or the selection of suitably resistant construction materials are necessary. In this study, we investigated that the cavitation erosion - corrosion damage under vibratory cavitation can be reduced by adding of side now velocity to the cavitation bubble group in order to eliminate bubbles formed in sea water environment.

• Journal of Fisheries and Marine Sciences Education
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• v.10 no.2
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• pp.226-238
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• 1998

With the advent of high speed and high output diesel engines, cavitation erosion-corrosion of wet cylinder liners is one of the most prevalent types of failure. The cavitation erosion-corrosion at cylinder liners in water cooled diesel engines is considered to be to the collapse of cavitation bubbles attributed to the cylinder liner vibration. To suppress cavitation damage in cylinder liner, the addition of an inhibitor would be more general method and innovations such as the improvement in the geometric design of the equipment or the selection of suitably resistant construction materials are necessary. In this study, photomicrographs from vibratory facility cavitation specimens and from an eroded liner of a field diesel engine are compared. The behavior of cavitation bubbles grown in fluid is observed under vibration conditions by taking direct photographs with high speed camera. In order to determine the contributions of pure cavitation erosion and of pure corrosion to the total cavitation damage are be studied by following an experimental programme which includes three types of test: (1)pure cavitation erosion test, (2)pure corrosion test, and (1)cavitation erosion-corrosion test. Also cavitation damage under vibratory cavitation is reduced by using flow in tap water.

• Corrosion Science and Technology
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• v.4 no.5
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• pp.178-190
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• 2005

In order to develop a new corrosion sensor for detecting and monitoring the external and internal corrosion damage of buried pipeline, the electrochemical property of sensors and the correlation of its output to corrosion rate of steel pipe, were evaluated by electrochemical methods in two soils of varying resistivity (5,000 ohm-cm, 10,000 ohm-cm) and synthetic tap water environments. In this paper, two types of galvanic probes were manufactured: copper-pipeline steel (Cu-CS) and stainless steel-pipeline steel (SS-CS). The corrosion behavior in synthetic groundwater and synthetic tap water for the different electrodes was investigated by potentiodynamic test. The comparison of the sensor output and corrosion rates revealed that a linear relationship was found between the probe current and the corrosion rates. In the soil resistivity of $5,000{\Omega}-cm$ and tap water environments, only the Cu-CS probe had a good linear quantitative relationship between the sensor output current and the corrosion rate of pipeline steel. In the case of $10,000{\Omega}-cm$, although the SS-CS probe showed a better linear correlation than that of Cu-CS probe, the Cu-CS probe is more suitable than SS-CS probe due to the high current output.

• Corrosion Science and Technology
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• v.22 no.6
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• pp.435-446
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• 2023

Corrosion behaviors of laser-welded super duplex stainless steel (SDSS) tubes after exposure to an actual power plant environment for one year and those of fin-tube welded SDSS were evaluated. Results showed that corrosion damage on the back side of the SDSS tube in the direction of hot air was higher than that on the front side regardless of weldment location. However, corrosion damage showed no difference between weldment and base metal due to recovery of phase fraction in the weldment through post weld heat treatment (PWHT). Nevertheless, the SDSS tube showed severe corrosion damage along grain boundary due to surface phase transformation (δ → γ) and Cr₂N precipitation caused by PWHT with a high N₂ atmosphere. Corrosion resistance of the SDSS tube was recovered when degraded surface was removed. Corrosion sensitivity of a fin-tube increased significantly due to pre-existing crevice, unbalanced phase fraction, and σ phase precipitation adjacent to the fusion line. Although corrosion resistance was improved by recovered phase fraction and sufficient dissolution of σ phase during PWHT, corrosion reaction was concentrated at the pre-existing crevice. These results suggest that welding conditions for fin-tube steel should be optimized to improve corrosion resistance by removing pre-existing crevice in the weldment.

• Journal of the Korean institute of surface engineering
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• v.48 no.6
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• pp.354-359
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• 2015

Stainless steel has poor corrosion resistance in marine environment due to the breakdown of a passive film caused by chloride. It suffers electrochemical corrosion like pitting corrosion, crevice corrosion, and stress corrosion crack (SCC) in marine environment. In general, it indicates that the passive film of $Al_2O_3$ has better corrosion resistance than that of $Cr_2O_3$ in seawater. This paper investigated the damage behavior 304 stainless steel and hot-dip aluminized 304 stainless steel in seawater solution. Various electrochemical experiments were carried out including potential measurement, potentiodynaimic experiment, Tafel analysis and galvanostatic experiment. As a result of anodic polarization experiment, higher pitting damage depth was indicated at 304 stainless steel than hot-dip aluminized 304 stainless steel. In addition, relatively higher corrosion current density was shown at hot-dip aluminized stainless steel as a result of Tafel analysis.

• Journal of Ship and Ocean Technology
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• v.2 no.1
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• pp.58-70
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• 1998

Many bulk carrier losses have been reported of late, and one of the possible causes of such casualties is thought to be the structural failure of aging hulls in rough weather. Clearly, in such cases, vessels that start out belong adequate somehow become marginal later in life. Fatigue and corrosion related potential problems may be the most important factors affecting such age related vessel damage. With respect to fatigue, extensive studies have been done worldwide both experimentally and theoretically, and the results have been applied to some extent. However, in the case of corrosion effects, additional research is still needed to better understand, clarify and address the various strength uncertainties and their effects on structural behavior. This paper develops a probabilistic corrosion rate estimation model for the longitudinal strength members of bulk carriers. The model is based on available statistical data for corrosion of existing bulk carriers. The corrosion data collected are documented for future use.

• Smart Structures and Systems
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• v.5 no.4
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• pp.443-455
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• 2009

The use of fiber reinforced polymer (FRP) reinforcement in concrete structures has been on the rise due to its advantages over conventional steel reinforcement such as corrosion. Reinforcing steel corrosion has been the primary cause of deterioration of reinforced concrete (RC) structures, resulting in tremendous annual repair costs. One application of FRP reinforcement to be further explored is its use in RC frames. Nonetheless, due to FRP's inherently elastic behavior, FRP-reinforced (FRP-RC) members exhibit low ductility and energy dissipation as well as different damage mechanisms. Furthermore, current design standards for FRP-RC structures do not address seismic design in which the beam-column joint is a key issue. During an earthquake, the safety of beam-column joints is essential to the whole structure integrity. Thus, research is needed to gain better understanding of the behavior of FRP-RC structures and their damage mechanisms under seismic loading. In this study, two full-scale beam-column joint specimens reinforced with steel and GFRP configurations were tested under quasi-static loading. The control steel-reinforced specimen was detailed according to current design code provisions. The GFRP-RC specimen was detailed in a similar scheme. The damage in the two specimens is characterized to compare their performance under simulated seismic loading.

• Nuclear Engineering and Technology
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• v.52 no.6
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• pp.1222-1230
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• 2020

The corrosion rates of the reactor pressure vessel materials of SA508 Grade 3 were measured using a weight loss method in aerated boric acid solutions to simulate the evaporation of leaked PWR primary water in an ambient environment. The corrosion behavior and products were examined using X-ray diffraction and electron microscopy. SA508 showed typical general corrosion characteristics. The corrosion rate increased steadily as the boron concentration was increased. As the immersion time elapsed, the corrosion rate slowly or rapidly decreased according to the oxidation reaction of iron. The corrosion rate showed a complicated pattern depending on the temperature; it increased gradually and then rapidly decreased again when reaching a certain transition temperature. The corrosion products of SA508 were found to be FeO(OH), Fe₂O₃, and Fe₃O₄. As the boron concentration decreased and the temperature was increased, the formation of Fe₃O₄ was more favorable as compared to the formation of FeO(OH) and Fe₂O₃. Consequently, the changes of the corrosion rate and behavior were closely related to the oxidation reaction of iron on the surface. The corrosive damage to SA508 appears to be most severe when the oxidation reaction is such that Fe₂O₃ forms as a corrosion product.