• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.05a
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• pp.307-308
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• 2021

Corrosion of reinforced steel inside concrete is an important cause of performance degradation of reinforced concrete structures and has a profound influence on the durability of structures. In this study, three groups of different reinforced concrete structures exposed to the natural environment were subjected to chloride ion accelerated corrosion tests for up to 180 days. The corrosion velocity and ambient temperature of the samples were measured and recorded every day. Based on Faraday's law, the corrosion speed of steel bars could be measured, and the ambient temperature and humidity around the structure in corresponding time were compared. Through the measurement of up to 180 days, the influence of external ambient temperature and humidity on the corrosion speed of steel bars inside the concrete structure was found out. The results show that there is a good direct proportional relationship between temperature and corrosion speed. When the ambient temperature increases by 15℃, the corrosion rate increases by about one time.

• Corrosion Science and Technology
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• v.13 no.1
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• pp.28-35
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• 2014

Recently, the fuel oil of diesel engines of marine ships has been increasingly changed to heavy oil of low quality as the oil price is getting higher and higher. Therefore, the spiral gear attached at the motor of the oil purifier which plays an important role to purify the heavy oil is also easy to expose at severe environmental condition due to the purification of the heavy oil in higher temperature. Thus, the material of the spiral gear requires a better mechanical strength, wear and corrosion resistance. In this study, the heat treatment(tempering) with various holding time at temperature of $500^{\circ}C$ was carried out to the alloy of Cu-7Al-2.5Si as centrifugal casting, and the properties of both hardness and corrosion resistance with and without heat treatment were investigated with observation of the microstructure and with electrochemical methods, such as measurement of corrosion potential, cathodic and anodic polarization curves, cyclic voltammogram, and a.c. impedance. in natural seawater solution. The ${\alpha}$, ${\beta}^{\prime}$ and ${\gamma}_2$ phases were observed in the material in spite of no heat treatment due to quenching effect of a spin mold. However, their phases, that is, ${\beta}^{\prime}$ and ${\gamma}_2$ phases decreased gradually with increasing the holding time at a constant temperature of $500^{\circ}C$. The hardness more or less decreased with heat treatment, however its corrosion resistance was improved with the heat treatment. Furthermore, the longer holding time, the better corrosion resistance. In addition, when the holding time was 48hrs, its corrosion current density showed the lowest value. The pattern of corroded surface was nearly similar to that of the pitting corrosion, and this morphology was greatly observed in the case of no heat treatment. It is considered that ${\gamma}_2$ phase at the grain boundary was corroded preferentially as an anode. However, the pattern of general corrosion exhibited increasingly due to decreasing the ${\gamma}_2$ phase with heat treatment. Consequently, it is suggested that the corrosion resistance of Cu-7Al-2.5Si alloy can be improved with the heat treatment as a holding time for 48 hrs at $500^{\circ}C$.

• Journal of the Korean institute of surface engineering
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• v.36 no.4
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• pp.307-316
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• 2003

Salt spray, CASS(copper accelerated acetic salt spray) and EC(electrolytic corrosion) tests were performed in order to evaluate the corrosion resistance of plated Ni and Ni-Cr layers on Fe substrate. Compared with the conventional methods such as salt spray and CASS, the electrochemical method such as EC test may be beneficial in terms of test time span and quantitative accuracy. Furthermore, EC test can also become the alternative method to evaluate the resistance to corrosion of coatings by measuring the corrosion potentials of the coated layers in the electrolyte during the off-time of EC cycles. Compared with the corrosion potentials of pure iron, nickel, chromium, those potentials of coated layers can be used to anticipate the extent of corrosion. Results showed that in terms of the test time span, EC test gave 14 times and 21 times faster results than the salt spray test in cases of $5\mu\textrm{m}$ Ni and $20\mu\textrm{m}$ Ni plated layers, respectively. In addition, EC test also offered the shorter test time span than CASS test in cases of $5 \mu\textrm{m}$ Ni + $0.5\mu\textrm{m}$ Cr, and $20\mu\textrm{m}$ Ni + $0.5\mu\textrm{m}$ Cr on Fe substrate by 78 times and 182 times, respectively. Therefore, EC test can be regarded as the better method to evaluate the resistance to corrosion of coated layers than the conventional methods such as salt spray and CASS.

• Corrosion Science and Technology
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• v.13 no.6
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• pp.214-223
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• 2014

Interest in the durability assessment and structural performance has increased according to an increase of concrete structures in salt damage environment recent years. Reliable way ensuring the most accelerated corrosion test is a method of performing the rebar corrosion monitoring as exposed directly to the marine test site exposure. However, long-term exposure test has a disadvantage because of a long period of time. Therefore, many studies on reinforced concrete in salt damage environments have been developed as alternatives to replace this. However, accelerated corrosion test is appropriate to evaluate the critical chlorine concentration in the short term, but only accelerated test method, is not easy to get correct answer. Accuracy of correlation acceleration test depends on the period of the degree of exposure environments. Therefore, in this study, depending on the concrete mix material, by the test was performed on the basis of the composite degradation of the salt damage, and investigate the difference of corrosion initiation time of the rebar, and indoor corrosion time of the structure, of the marine environment of the actual environments were inuestigated. The correlation coefficient was derived in the experiment. Long-term exposure test was actually conducted in consideration of the exposure conditions submerged zone, splash zone and tidal zone. The accelerated corrosion tests were carried out by immersion conditions, and by the combined deterioration due to the carbonation and accelerated corrosion due to wet and dry condition.

• Structural Engineering and Mechanics
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• v.42 no.4
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• pp.531-549
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• 2012

Numerous oil tanker losses have been reported and one of the possible causes of such casualties is caused by the structural failure of aging ship hulls in rough weather. In aging ships, corrosion and fatigue cracks are the two most important factors affecting structural safety and integrity. This research is about effect on hull girder ultimate strength behavior of double hull oil tanker according to corrosion after Part I: stiffened panel. Based on corrosion data of Part I (time-dependent corrosion wastage model and CSR corrosion model), when progressing corrosion of fourtypes of double hull oil tankers (VLCC, Suezmax, Aframax, and Panamax), the ultimate strength behavior of hull girder is compared and analyzed. In case of the ultimate strength behavior of hull girder, when occurring corrosion, the result under vertical and horizontal bending moment is analyzed. The effect of time-dependent corrosion wastage on the ultimate hull girder strength as well as the area, section modulus, and moment of inertia are also studied. The result of this research will be useful data to evaluate ultimate hull girder strength of corroded double hull oil tanker.

• Korean Journal of Materials Research
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• v.9 no.2
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• pp.205-210
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• 1999

The 250ppm hydrogen-charged Zircaloy-4 sheets, homogenized at $400^{\circ}C$ for 72hrs in vacuum, were corroded under the autoclave conditions of $350^{\circ}C$, 2350psi. The corrosion behavior of the Zircaloy-4 sheets was evaluated by measuring their weight gains with the exposure time. The electrical characteristics were investigated in the ranges of 5000~1x10\ulcornerHz using AC impedance technique in 1N $H_2$$SO_4$aqueous solution. The corrosion rate of the hydrogen charged specimen was more rapid than the normal specimen at the early stage of the corrosion. With a longer corrosion time, however, the normal specimen corroded faster than the hydrogen-charged specimen. At the same time the hydrogen pickup in the hydrogen-charged specimen was more suppressed compared with the normal specimen. Such appears to be occurred because the impedance for the movement of the hydrogen ion into the metal was higher in the hydrogen-charged specimen compared to normal specimen at the interface between the oxide layer and the uncorroded metal. Thus the corrosion rate of the hydrogen-charged specimen was likely to be decreased with a longer corrosion time.

• Journal of the Society of Disaster Information
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• v.4 no.1
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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.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.873-876
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• 2002

This paper presents the effect of internal corrosion, external corrosion, material properties, operation condition, earthquake, traffic load and design thickness in pipeline on the failure prediction using a failure probability model. A nonlinear corrosion is used to represent the loss of pipe wall thickness with time. The effects of environmental, operational, and design random variables such as a pipe diameter, earthquake, fluid pressure, a corrosion rate, a material yield stress and a pipe thickness on the failure probability are systematically investigated using a failure probability model for the corrosion pipeline.

• Proceedings of the Korean Reliability Society Conference
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• 2002.06a
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• pp.403-410
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• 2002

This paper presents the effect of internal corrosion, external corrosion, material properties, operation condition, earthquake, traffic load and design thickness in pipeline on the failure prediction using a failure probability model. A nonlinear corrosion is used to represent the loss of pipe wall thickness with time. The effects of environmental, operational, and design random variables such as a pipe diameter, earthquake, fluid pressure, a corrosion rate, a material yield stress and a pipe thickness on the failure probability are systematically investigated using a failure probability model for the corrosion pipeline.

• Corrosion Science and Technology
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• v.7 no.5
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• pp.296-299
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• 2008

High order statistical parameters were evaluated using the electrochemical noise data collected during corrosion of type 430 stainless steel coupled to a inert, platinum electrode in 3.5% NaCl solution. High order statistical parameters are shown to predict uniform corrosion properly. However, Localization index, skewness of current, kurtosis and skewness of potential are capable of predicting pitting corrosion only when the transients are large with long life time. Of the high order statistical parameters evaluated, kurtosis of current is found to be the most sensitive parameter for detecting uniform and pitting corrosion.