• Journal of Advanced Marine Engineering and Technology
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• v.13 no.4
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• pp.54-62
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• 1989

When some kinds of inhibitors, i.e. $1{\times}10{-3}mol/l$ arsenic trioxide, 0.2 mol/l 2-mercaptoethanol, 0.2mol/l thiourea were added to 3% NaCl solution, there were some considererable effects to decrease corrosion current density in natural potential condition and the effect fo solution temperature increasing corrosion rate was smaller than that of no addition to 3% NaCl solution. However the susceptibility of hydrogen embrittlement due to over-protection in case of cathodic protection was much greater than that of no addition, especially was the greatest in case of addition of 2-mercaptoethanol. Therefore adding inhibitors for anti-corrosion effect, it is suggested that selection of the optimum protection potential is important from the view point of prevention against hydrogen embrittlement due to over-protection in case of cathodic protection.

• Journal of the Korean Professional Engineers Association
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• v.17 no.1
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• pp.9-19
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• 1984

• Journal of the Korean Professional Engineers Association
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• v.20 no.2
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• pp.3-15
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• 1987

• Corrosion Science and Technology
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• v.14 no.4
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• pp.177-183
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• 2015

Prestressed Concrete steel Cylinder Pipe (PCCP) is extensively used as seawater pipes for cooling in nuclear power plants. The internal surface of PCCP is exposed to seawater, while the external surface is in direct contact with underground soil. Therefore, materials and strategies that would reduce the corrosion of its cylindrical steel body and external steel wiring need to be employed. To prevent against the failure of PCCP, operators provided a cathodic protection to the pre-stressing wires. The efficiency of cathodic protection is governed by the anodic performance of the system. A mixed metal oxide (MMO) electrode was developed to meet criteria of low over potential and high corrosion resistance. Increasing coating cycles improved the performance of the anode, but cycling should be minimized due to high materials cost. In this work, the effects of $RuCl_3$ concentration on the electrochemical properties and lifespan of MMO anode were evaluated. With increasing concentration of $RuCl_3$, the oxygen evolution potential lowered and polarization resistance were also reduced but demonstrated an increase in passive current density and oxygen evolution current density. To improve the electrochemical properties of the MMO anode, $RuCl_3$ concentration was increased. As a result, the number of required coating cycles were reduced substantially and the MMO anode achieved an excellent lifespan of over 80 years. Thus, we concluded that the relationship between $RuCl_3$ concentration and coating cycles can be summarized as follows: No. of coating cycle = 0.48*[$RuCl_3$ concentration, $M]^{-0.97}$.

• Journal of the Korean Institute of Gas
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• v.12 no.1
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• pp.19-24
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• 2008

Due to industrialization and urbanization, underground metallic utilities with different owners have been rapidly increased and cathodic protection (CP) methods, especially impressed current CP systems, have been widely adopted to protect their utilities from corrosion with expanded recognition of this method. The stray current interference problem as well as the difficulty in spatial security for system installation, however, came to a ramification of which each owner couldn't resolve for himself. In this respect, this paper illustrates a field-diagnosed example for mutual interference due to separately operated CP systems and suggests an alternative method to overcome the interference situation by design and field-assessment of a common anode bed cathodic protection system.

• Corrosion Science and Technology
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• v.16 no.3
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• pp.109-114
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• 2017

Monitoring of corrosion is in most cases based on simulation of environmental conditions on a large and complex structure such as a buried pipeline using a small probe, and the measurement of thermodynamics and kinetics of corrosion processes occurring on the probe surface. This paper presents a hybrid corrosion monitoring probe designed for simulating deteriorating conditions wrought by disbonded coatings and for measuring current densities and distribution of such densities on a simulated pipeline surface. The concept of the probe was experimentally evaluated using immersion tests under cathodic protection (CP) in high resistivity aqueous solution. Underneath the disbonded area, anodic currents and cathodic currents were carefully measured. Anodic current densities were used to calculate metal loss according to Faraday's law. Calculated corrosion patterns were compared with corrosion damage observed at the surface of the probe after a series of stringent tests. The capability of the probe to measure anodic current densities under CP, without requiring interruption, was demonstrated in high resistivity aqueous solution. The pattern of calculated metal loss correlated well with corrosion products distribution observed at the array surface. Working principles of the probe are explained in terms of electrochemistry.

• 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.

• Korean Journal of Materials Research
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• v.5 no.7
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• pp.842-849
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• 1995

The effect of cathodic protection by the sacrificial anode attached to condenser waterbox of power plant was investigated using numerical analysis. The condenser is consisted of various materials. So in case of no protection, the serious galvanic corrosion between waterbox and tubesheet was observed. If sacrificial anodes were attached to the wall of waterbox or the area corroded galvanically, the large protection effect was showed. To demonstrate the validity of numerical analysis results, model test was executed. The numerical solution was consistent with the experimental vague well.

• Journal of Korean Port Research
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• v.12 no.1
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• pp.145-154
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• 1998

Protection characteristics of the corroded steel pile which was served as a pier structure over 8 years in seawater have been examined in terms of corrosion potential, electrochemical impedance spectroscopy(EIS) and anodic/cathodic polarization curves. The steel structure was sectioned into two parts, waterline(splash zone, just above the seawater surface) and in-water(underwater), and protection characteristics for the two parts were investigated with the application of cathodic protection(CP) by sacrificial anodes using Zn and Al alloys. The main results obtained were as follows; (1) The corrosion potential of waterline zone was higher than that of in-water, which implied that the corrosion of waterline was more severe than that of in-water, (2) As a result of EIS examination, the transition period from the apparent CP to the substantial CP took about twenty to thirty days according to the corrosion condition.

• Corrosion Science and Technology
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• v.4 no.6
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• pp.242-249
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• 2005

A lot of parts in FGD (Flue Gas Desulfurization) systems of fossil-fuel power plants show the environments in which are highly changeable and extremely acidic corrosive medium according to time and locations, e.g. in duct works, coolers and re-heaters etc. These conditions are formed when system materials are immersed in fluid that flows on them or when exhausted gas is condensed into thin layered acidic medium to contact materials of the system walls and roofs. These environments make troublesome corrosion and air pollution problems that are occurred from the leakage of the condensed solution. To cathodically protect the metallic structures in extremely acidic fluid, the properties of the protective coatings on the metal surface were very important, and epoxy Novolac coating was applied in this work. On the base of acid immersion tests, hot sulfuric acid decreased the hardness of the coatings and reduced greatly the content of $Na_2O$, $Al_2O_3$, and $SiO_2$ among the main components of the coating. A special kind of CP(Cathodic Protection) system has been developed and tested in a real scale of the FGD facility. Applied coating for this CP system was peeled off and cracked in some parts of the facility. However, the exposed metal surface to extremely acidic fluid by the failure of the coatings was successfully protected by the new CP system.