• Magazine of the Korea Concrete Institute
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• v.11 no.2
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• pp.221-230
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• 1999

Corrosion of rebars can occur if there are cracks, moisture and availability of oxygen or carbonation proceeds, chloride penetrates and diffuses in concrete. Once rebars in concrete corrodes, subsequently accompanied with scaling, spalling in concrete cover. As a result of them, the RC structure is seriously deteriorated. In this study, theoretical review and experiments for cathodic protection(CP) have been performed to control corrosion of rebars in concrete contained chlorides and pre-crack. For CP the impressed current system was applied, the protection effect was investigated when rebars was directly contacted with salt water due to crack and open to much chlorides in concrete. In order to investigate the effect of protection, when CP was energized for 1 year, half-cell potential, potential-decay with current density, corrosion ratio, etc. were measured. With the cathodic protection by impressed current system, the depolarized values of all specimen were met NACE Standard, the effect of 34~84% of the ratio of corrosion area and 84~86% of cross-section reduction were calculated.

• Corrosion Science and Technology
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• v.16 no.2
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• pp.49-58
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• 2017

Many research efforts on the effect of nitrogen on the corrosion resistance of stainless steels have been reported, but little research has been conducted on the effect of nitrogen for the weldment of stainless steels by the seal-weld method. Therefore, this work focused on the determining the corrosion resistance of tube/tube sheet mock-up specimen for sea water condensers, and elucidating the effect of shielding nitrogen gas on its resistance. The pitting corrosion of autogenously welded specimen propagated preferentially along the dendritic structure. Regardless of the percent of shielding nitrogen gas, the analyzed nitrogen contents were very much lower than that of the bulk specimen. This can be arisen because the nitrogen in shielding gas may partly dissolve into the weldment, but simultaneously during the welding process, nitrogen in the alloy may escape into the atmosphere. However, the pitting resistance equivalent number (PREN) of the interdendrite area was higher than that of the dendrite arm, regardless of the shielding gas percent; and the PREN of the interdendrite area was higher than that of the base metal; the PREN of the dendrite arm was lower than that of the base metal because of the formation of (Cr, Mo) rich phases by welding.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.675-678
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• 1999

Rebar corrosion in concrete containing both chloride ions and calcium nitrite inhibitors were investigated by the various electrochemical methods. Rebar corrosion was accelerated by applying the impressed current to the rebar in concrete. Effect of chloride content and inhibitors on rebar corrosion were evaluated. Accelerated corrosion technique is the method to measure the time to the initiation of cracks of reinforced concretes, by applying constant voltage between rebar and the stainless steel cathedes. The increase of concentration of chloride ions in concrete result in the increase in anodic currents and the reduction of time to crack. However addition of inhibitors did not improve corrosion resistance of rebar in concrete. Rebar corrosion in concrete with chloride ions and inhibitors was also analyzed by the immersed tests though the mesurement of corrosion potentials.

• Corrosion Science and Technology
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• v.14 no.6
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• pp.273-279
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• 2015

Effects of passive film quality by chemical passivation and solution flow on the corrosion behavior of 304 stainless steel in HCl solution were investigated using a coloration indicator, and by corrosion weight loss, electrochemical polarization and element dissolution measurements. A high redness degree suggests a low passive-film integrity for 304 stainless steel following air exposure, while the minimum redness degree for the samples after chemical passivation suggests a high passive-film integrity. In the static condition, samples subjected to air exposure exhibited a high corrosion rate and preferential dissolution of Fe. Chemical passivation inhibited the corrosion rate due to the intrinsically high structural integrity of the passive film and high concentrations of Cr-rich oxides and hydroxide. Solution flow accelerated corrosion by promoting both the anodic dissolution reaction and the cathodic reaction. Solution flow also altered the preferential dissolution to fast uniform dissolution of metal elements.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2006.06a
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• pp.95-96
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• 2006

ALDC 12 Al alloy is often corroded with some forms such as pitting corrosion, intergranular corrosion, and galvanic corrosion etc., in case of severe corrosion environment like seawater Annealing heat treatment was performed to improve the corrosion resistance of ALDC 12. Hardness was decreased with increasing of annealing temperature, however its corrosion resistance was clearly improved with increasing of annealing temperature.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• v.4 no.4
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• pp.255-261
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• 2000

Experiments were carried out to measure the corrosion potential and current density variations in the polarization curves of polypropylene. In particular, the results were examined to identify those influences affecting the corrosion potential, such as temperature, pH, salt, and oxygen. The Tafel slope for the anodic dissolution was determined based on the polarization effect under various conditions. Furthermore, the optimum conditions for the most rapid transformation were establish based on a variety of conditions, including temperature, pH, corrosion rate, and resistance of corrosion potential. The second anodic current density peak and maximum passive current density were designated as the critical corrosion sensitivity(I(sub)r/I(sub)f). This I(sub)r/I(sub)f value was then used to measure the critical corrosion sensitivity of polypropylene. The potentiodynamic parameters of corrosion were obtained using a Tafel plot.

• Structural Engineering and Mechanics
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• v.47 no.6
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• pp.773-790
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• 2013

Bending behaviors of corroded reinforced concrete (RC) beams under repeated loading were investigated experimentally. A total of twenty test specimens, including four non-corrosion and sixteen corrosion reinforced concrete beams, were prepared and tested. A numerical model for flexural and cracking behaviors of the beam under repeated loading was also developed. Effects of steel corrosion on reinforced concrete beams regarding cracking, mid-span deflection, stiffness and bearing capacity of corroded beams were studied. The impact of corrosion on bond strength as the key factor was investigated to develop the computational model of flexural capacity. It was shown from the experimental results that the bond strength between reinforcement and concrete had increased for specimen of low corrosion levels, while this effect was changed when the corrosion level was higher. It was indicated that the bearing capacity of corrosion beam increased even at a corrosion level of about 5%.

• Journal of Surface Science and Engineering
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• v.36 no.3
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• pp.272-283
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• 2003

Mild steel and zinc specimens were tested in five atmospheric testing sites of Vietnam in order to collect the corrosion databank as well as to study the corrosion mechanism in tropical conditions, in period of 1997-2000. The results obtained showed that the corrosion rate of steel is in the range of $10-50\;{\mu}m/year$ and of zinc is of $1-5\;{\mu}m/year$. They are interpretable in the comparison with the data obtained in different countries in the South East Asian as well as previous reports of Vietnamese nation project In atmospheric corrosion. The main factors affecting the corrosion in Vietnam tropical conditions are TOW (time of wetness) and salinity. The relationship between sulfur dioxide and corrosion of metals, particularly, zinc was not found clearly. An explanation was suggested about the complex effect of different pieces present in tropical atmosphere and about the alternative of the dominant factors such as humidity, salinity or temperature.

• Corrosion Science and Technology
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• v.8 no.6
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• pp.232-237
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• 2009

Copper tubes are widely used in the distribution systems of drinking water throughout the world because of their excellent corrosion resistance, high thermal conductivity, and ease of fabrication. However, corrosion problems from copper tubes as blue water phenomenon and leakage have been reported appreciably. The effect of pH on the corrosion behavior of copper tube for tap water was investigated by electrochemical voltammetric techniques in synthetic tap water. And the copper corrosion cases were discussed from the viewpoint of factors affecting the corrosion rate such as pH, alkalinity, LSI(Langelier Saturation Index), and concentration of bicarbonate and dissolved carbon dioxide.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.11a
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• pp.111-112
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• 2022

In this present study, the corrosion mitigation effect of conifer cone extract (CC) was examined in the cement mortar to improve the steel rebar (SR) corrosion resistance. The corrosion inhibition properties of the SR embedded in cement mortar (CM) admixed with different percentage (0, 0.5, 1.0, 1.5, 2.0 %) of CC was studied by open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) tests. This result confirms that the CM with 0.5% of CC added has better corrosion resistance than the blank specimen (0 % of CC). Although, the percentage of CC increase above 0.5%, the CC could yield a negative impact on CM properties in terms of reducing the corrosion resistance due to the reduction of cement hydration reaction. It was highlighted that the SR embedded in CM containing 0.5% of CC had increased corrosion resistance.