• Corrosion Science and Technology
• /
• 제19권5호
• /
• pp.231-238
• /
• 2020

Radioactive corrosion product specimens were analyzed using an electron probe microanalyzer (EPMA) and X-ray image mapping. It is difficult to analyze the composition of radioactive corrosion products using an EPMA due to the size and rough shape of the surfaces. It is particularly challenging to analyze the composition of radioactive corrosion products in the form of piled up, small grains. However, useful results can be derived by applying a semi-quantitative analysis method using an EPMA with X-ray images. A standard-less, semi-quantitative method for wavelength dispersive spectrometry. EPMA analysis was developed with the objective of simplifying the analytical procedure required. In this study, we verified the reasonable theory of semi-quantitative analysis and observed the semi-quantitative results using a sample with a good surface condition. Based on the validated results, we analyzed highly rough-surface radioactive corrosion products and assessed their composition. Finally, the usefulness of the semi-quantitative analysis was reviewed by verifying the results of the analysis of radioactive corrosion products collected from spent nuclear fuel rods.

• Corrosion Science and Technology
• /
• 제18권4호
• /
• pp.138-147
• /
• 2019

Pipes and components of the secondary system in the pressurized water reactor (PWR) are mainly comprised of manufactured carbon steel. Thus, the generated carbon steel corrosion products are transported into the steam generator and deposited, thereby deteriorating the integrity of the steam generator. Environmental condition in the secondary system of the PWRs differs across different locations. So, the corrosion rate and types of corrosion products depend on specific locations in the secondary system. In this study, the quantity and chemical compositions of corrosion products generated in various locations that vary in different temperatures and chemistry conditions were investigated. As a result of evaluating the PWR "Unit A" that is in current operation, the amount of corrosion products generated in the section of high temperature feedwater system was identified as the largest source in the secondary system. Major components of corrosion products were iron oxides such as magnetite, hematite, and lepidocrocite.

• Corrosion Science and Technology
• /
• 제7권2호
• /
• pp.99-111
• /
• 2008

Copper was exposed unsheltered and sheltered in four humid tropical sites, representing urban, urban-industrial, urban-marine and rural environments. The corrosion rates and the sequence of corrosion product formation are presented and discussed in relation with climatic and atmospheric pollution parameters. Chemical compositions of corrosion products were found to depend on environments and duration of exposure. In all environments, cuprite was the predominating corrosion product that formed first and continuously increased during the exposure. Among the sulphur-containing corrosion products, posnjakite and brochantite were more frequently found and the first formed earlier. Nantokite was the most common chlorine-containing products for most cases, except the high-chloride environment, where atacamite was detected instead. The corrosion rate of copper was well indicated by the colour of patina. The red-purple colour corresponded to the high corrosion rate and the greenish grey colour corresponded to the low corrosion rate. Corrosion rate of sheltered copper in urban-marine environment increased with the exposure time.

• 상하수도학회지
• /
• 제22권3호
• /
• pp.379-387
• /
• 2008

The pH & alkalinity adjustment method by lime and carbon dioxide($CO_2$) for corrosion control in water distribution system was investigated to evaluate the corrosion characteristics of metal pipes, such as galvanized iron, copper, stainless steel, and carbon steel. When the pH in sand filtered and ozone+GAC treated water was increased with lime and $CO_2$ from 7.5 to 8.0, the concentration of residual chlorine decreased at higher pH and longer reaction time; the concentration of trihalomethane increased. The corrosion rate of coupons with corrosion control using lime and carbon dioxide was showed much smaller than those without corrosion control using pilot-scale simulated distribution system. The galvanized iron was corroded much faster than carbon steel, copper, and stainless steel. Especially, copper and stainless steel coupons were hardly corroded. The galvanized iron and carbon steel coupons with corrosion control were produced the corrosion products less than those without corrosion control by the results of environmental scanning electron microscope(ESEM) and energy dispersive x-ray spectroscopy(EDS) analyses. The galvanized iron coupon with pH and alkalinity adjustment by lime and carbon dioxide was detected about 30 percent of zinc, when the carbon steel was detected about 30 percent of calcium by calcium carbonate products formation. For the results of X-ray diffraction(XRD) analyses, the goethite(${\alpha}$-FeOOH) was identified as primary corrosion product of galvanized iron without corrosion control, while the Zinc oxide(ZnO) was found on corrosion products of galvanized iron coupon with corrosion control as the results of EDS analyses. However, the carbon steel corrosion products regardless of corrosion control were composed predominantly of maghemite(${\gamma}-Fe_2O_3$) and hematite(${\alpha}-Fe_2O_3$).

• Corrosion Science and Technology
• /
• 제10권5호
• /
• pp.175-179
• /
• 2011

The transportation and deposition of iron corrosion products are important elements that affect both the steam generator (SG) integrity and secondary system in pressurized water reactor (PWR) nuclear power plants. Most of iron corrosion products are generated on carbon steel materials due to flow accelerated corrosion (FAC). The several parameters like water chemistry, temperature, hydrodynamic, and steel composition affect FAC. It is well established that the at-temperature pH of the deaerated water system has a first order effect on the FAC rate of carbon steels through nuclear industry researches. In order to reduce transportation and deposition of iron corrosion products, increasing pH(t) tests were applied on secondary system of A, B units. Increasing pH(t) successfully reduced flow accelerated corrosion. The effect of increasing pH(t) to inhibit FAC was identified through the experiment and pH(t) evaluation in this paper.

• Nuclear Engineering and Technology
• /
• 제36권6호
• /
• pp.549-558
• /
• 2004

TTo comply with increasingly strict regulations for protection against radiation exposure, many nuclear power plants have been working ceaselessly to reduce and control both the radiation sources within power plants and the radiation exposure experienced by operational and maintenance personnel. Many research studies have shown that deposits of irradiated corrosion products on the surfaces of coolant systems are the main cause of occupational radiation exposure in nuclear power plant. These corrosion product deposits on the fuel-clad surface are also known to be main factors in the onset of axial offset anomaly (AOA). Hence, there is a great deal of ongoing research on water chermistry and corrosion processes. In this study, a magnetic filter with permanent magnets was devised to remove the corrosion products in the coolant stream by taking advantage of the magnetic properties of the corrosion products demonstrated a removal efficiency of over 90% for particles above 5${\mu}m$. This finding led to the construction of an electromagnetic device that causes the metallic particulates to flocculate into larger aggregates of about 5${\mu}m$ in diameter by using a novel application of electromagnetic flocculation on radioactive corrosion products.

• 보존과학회지
• /
• 제26권4호
• /
• pp.407-416
• /
• 2010

토양 중에 존재하는 철환원능력을 갖춘 세균은 철제유물의 부식생성물을 에너지원으로 이용할 수 있다. 이러한 세균의 활동은 부식생성물의 변화를 초래하여 유물의 부식을 촉진시키는 부식생성물의 판단을 어렵게 할 수 있다. 본 연구의 목적은 철환원세균이 부식생성물에 일으키는 변화를 조사하여, 철제유물의 부식에 관한 이해를 높이고자 한다. 실험은 출토철제유물을 재현하기 위해서 부식촉진인자 중에서 가용성염류(염화물이온, 황산이온)를 이용하여 부식시킨 철편을 준비하였다. 이 부식철편을 세균이 존재하는 배지에서 42일간 배양하였다. 실험 후, 부식철편의 부식생성물은 SEM, EDS, XRD를 이용하여 관찰, 분석을 실시하였다. 관찰결과, 부식철편이 세균의 활동으로 인해 녹색으로 변화하였으며 부식철편에 판상 결정과 마름모꼴 결정이 새롭게 생성된 사실을 알게 되었다.

• 보존과학연구
• /
• 통권16호
• /
• pp.59-111
• /
• 1995

Chemical composion and crystal form of Corrosion products found on archaeological iron objects were analyzed using X-ray fluorescence analysis, micro-X-ray powder diffraction analysis and ion chromatographic technique. The nature and behavior of the corrosion products were studied in order to aid in the conservation and restoration of burial iron objects. Twenty-two samples analyzed in this study were collected from iron object found in Korea and Japan. The corrosion products of iron objects from burial mounds contain $\alpha$-FeOOH, $\beta$-FeOOH, $\gamma$-FeOOH, $Fe_3O_4$and amorphous iron hydroxides. The content of $\alpha$-HeOOH is the greatest. Because, Ageing for long period should change the amorphous iron hydroxides is considerably less than that in usual atmospheric corrosion products. The concentration of chlorine and sulfine is remarkably variable ($Cl^-$ : 100- 30,000ppm, $SO_4^-2$ : 20-10,000ppm),but the reasons are unclear. The presence of generally high concentrations of chlorine and sulfine the corrosion products of iron objects seem to be influenced by the marine climatic condition. The presence of high chlorine and sulfine concentrations in the corrosion products of iron objects seem to be influenced by the marine burial environments.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
• /
• pp.361-366
• /
• 2002

The deterioration of concrete structure due to corrosion of the reinforcement has created big financial losses on the overall industries. The volume expansion of the corrosion products causes internal pressure to concrete wall around reinforcing bar. If the maximum principal stress induced by internal pressure exceeds the tensile strength of the concrete at any point of time, a crack forms at any point of material. Therefore, in terms of life assessment of concrete structure, it is very important to predict the amount of corrosion products which induces initial concrete cracking. With this objective, this paper proposes the critical amount of corrosion products at interface between reinforcement and concrete using finite element analysis. If an actual survey of corrosion rates could be made, the model might supply information for condition assessment of existing concrete structure. As the mechanical properties of corrosion product and instantaneous geometry of corroded steel are considered in the analysis, the value obtained will be more realistic.

• Corrosion Science and Technology
• /
• 제16권5호
• /
• pp.241-246
• /
• 2017

The comparative results of corrosion testing in humid tropical atmosphere in rural and coastal areas for hot dipped zinc coatings are presented below. The test was conducted in outdoor conditions over a period of five years. The mass loss and other performance characteristics of two types of zinc coatings were evaluated, analysed and discussed in relation to the climatic and environmental parameters. The corrosion rates of the coatings exposed to coastal conditions were about three times higher than the corrosion rates appreciated in rural conditions. The data demonstrates that the corrosion process obeys an equation of the form $M=At^n$, where M is the loss of metal and t is the time of exposure. A and n are constants which values depend on the environmental characteristics and the physicochemical behavior of the corrosion products respectively. Corrosion is strongly influenced by atmospheric time of wetness (TOW) and airborne salinity. The nature and composition of corrosion products are also considered. Simonkolleite, a major crystalline phase, was found in the zinc corrosion products exposed to coastal conditions, while zinc hydroxide and zinc hydrosulfate are easily found in rural settings.