• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.35 no.1
• /
• pp.46-51
• /
• 2007

In this study, test results for fatigue crack propagation of Al-2024-T3511 are presented considering corrosion effects, and fatigue lifes are compared for the cases of corrosion and non-corrosion. Higher corrosion environments show lower fatigue life and faster crack growth. To predict the corrosion fatigue life, a corrosion factor concept is newly introduced and applied in Paris' law. The predicted results show good agreement with experimental data and this corrosion fatigue model can be successfully used for the prediction of fatigue life of aluminum structure with corrosion effects.

• Korean Journal of Materials Research
• /
• v.8 no.6
• /
• pp.571-576
• /
• 1998

This study was carried out for investigating the corrosion behaviors, corrosion mechanisms, and behaviors of elements on a separator for a molten carbonate fuel cell under both the electrolyte and anode side environment. A 310S austenitic stainless steel was used as the separator material. Corrosion proceeded via three steps; the formation step of corrosion product in which rapid corrosion takes place until stable corrosion product is formed after the beginning of corrosion, the protection step against corrosion until breakaway occurs after the formation step of stable corrosion product and the advancing step of corrosion after the breakaway. From the standpoint of the behavior of the elements in the specimen, Fe and Cr, Ni were enriched in the region of corrosion product, in the region of corrosion protection, and at the Cr-deplete zone, respectively. With respect to corrosion mechanism, ionization of electrolyte at the anode side was the main corrosion mechanism, and the final corrosion products were $LiFeO_2$ and $LiCrO_2$ at the anode side.

• Journal of the Korea Concrete Institute
• /
• v.20 no.6
• /
• pp.741-746
• /
• 2008

Many methods have been introduced to protect the corrosion of embedded steel in RC structure. One of the methods that restrain corrosion of steel is corrosion inhibitor. The technology that delayed the progress of corrosion is developed recently by converting active rust to passive rust. However, the performance for concrete structure is not fully examined because this corrosion inhibitor is developed for normal metal product. In this study, the application of corrosion inhibitor that use tannin acid is investigated by concrete specimen. According to the results, tannin acid corrosion inhibitor does not occur reduction of workability and strength in concrete. When corrosion inhibitor is added more than 4% per cement weight, the penetration depth of chloride decrease about 10%. Also, corrosion resistance of concrete is improved because tannin acid corrosion inhibitor has an effect on converting the rust of steel into stable state. It is showed in special that the addition more than 6% is effective in corrosion resistance.

• Korean Journal of Heritage: History & Science
• /
• v.53 no.1
• /
• pp.24-33
• /
• 2020

In excavated bronze artifacts, corrosion products of various shapes and colors are observed due to multiple corrosion factors coexisting in the burial environment, and these corrosion products can constitute important data not only in terms of long-term corrosion-related information, but also in connection with preservation of artifacts. As such, scientific analysis is being carried out on the corrosion layer and corrosion products of bronze artifacts, and the corrosion mechanism and the characteristics of corrosion products elucidated, which is essential for interpreting the exposed burial environment and its association with corrosion factors inside the burial environment. In this study, after classifying excavated bronze artifacts according to alloy ratio and fabrication technique, comprehensive analysis of the surface of corrosion artifacts, corrosion layer, and corrosion products was carried out to investigate the corrosion mechanism, formation process of the corrosion layer, and characteristics of corrosion products. The study designated two groups according to alloy ratio and fabrication technique. In Group 1, which involved a Cu-Sn-Pb alloy and had no heat treatment, the surface was rough and external corrosion layers were formed on a part, or both sides, of the inside and the outside, and the surface was observed as being green or blue. α+δ phase selection corrosion was found in the metal and some were found to be concentrated in an empty space with a purity of 95 percent or more after α+δ phase corrosion. The Cu-Sn alloy and heat-treated Group 2 formed a smooth surface with no external corrosion layer, and a dark yellow surface was observed. In addition, no external corrosion layer was observed, unlike Group 1, and α corrosion was found inside the metal. In conclusion, it can be seen that the bronze artifacts excavated from the same site differ in various aspects, including the formation of the corrosion layer, the shape and color of the corrosion products, and the metal ion migration path, depending on the alloy ratio and fabrication technique. They also exhibited different corrosion characteristics in the same material, which means that different forms of corrosion can occur depending on the exposure environment in the burial setting. Therefore, even bronze artifacts excavated from the same site will have different corrosion characteristics depending on alloy ratio, fabrication technique, and exposure environment. The study shows one aspect of corrosion characteristics in specific areas and objects; further study of corrosion mechanisms in accordance with burial conditions will be required through analysis of the corrosive layer and corrosive product characteristics of bronze artifacts from various regions.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.11 no.6
• /
• pp.2306-2310
• /
• 2010

Corrosion is a complex series of oxidation/reduction reactions between at the water-metal surfaces and materials in which the water is stored or transported. With respect to the corrosion potential of drinking water, the primary concerns include the potential presence of toxic metals, such as lead and copper; deterioration and damage to the household plumbing, and aesthetic problems such as stained laundry, and bitter taste. This study was performed to evaluate the effects of corrosion inhibitors on corrosion rates, Fe and Cu release concentration in water distribution pipes. Decrease of corrosion rates were strongly related to phosphate corrosion inhibitors. Considering that typical corrosion processes consists of a series of electrochemical reaction at the metal surface in contact with water, corrosion rates were positively correlated with Fe release.

• Journal of Conservation Science
• /
• v.26 no.4
• /
• pp.407-416
• /
• 2010

Bacteria with ability for iron reduction in the soil can use corrosion products of iron remains as energy source. The activities of this bacteria cause the change of corrosion products. As a result, it can be difficult to identify corrosion products promoting corrosion of iron remains. The purpose of this study, is to investigate the change in corrosion products that bacteria causes and to improve understanding about the corrosion of iron remains. To simulate corroded condition of excavated iron remains, carbon steel corroded by solution of NaCl and $Na_2SO_4$ was prepared. Then the prepared carbon steel was immersed in a liquid medium with bacteria. The incubation period was 42days. After experiment, the carbon steel was analyzed by SEM-EDS, X-ray diffraction method. The result is that the carbon was changed to green because of activity of bacteria and that the plate crystal and lozenge crystal were generated on the corrosion specimen. Also, we confirmed that the activities of bacteria differenciated colors and forms of corrosion products.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.23 no.7
• /
• pp.16-24
• /
• 2019

The corrosion amounts of steel structures can be different depending on their installation condition and height. Thus, their corrosion maintenance should be considered depending on installation conditions of local structural members. In this study, an atmospheric exposure test was conducted to evaluate the corrosion amount and the corrosion rate depending on the installation condition and height of a steel water gate using monitoring steel plates and corrosion environment measuring sensors. The mean corrosion depth was evaluated using the weight loss method and the galvanic corrosion current was measured by corrosion environment measuring sensors. Local corrosion rate of local structural member in steel water gate was estimated using measured mean corrosion depths and galvanic corrosion currents. From this measurement results, the corrosion damage in horizontal member of the cross beam was highly evaluated than those of other structural member as skin plate, etc. The relative difference in the corrosion rate of a local structural member could be highly affected by local corrosion environments of steel water gate members. Therefore, an appropriate maintenance method should be considered for local corrosion damages of local structural members determined by local corrosion environments of a steel water gate.

• Proceedings of the KSME Conference
• /
• 2003.04a
• /
• pp.241-246
• /
• 2003

In order to develop a method of corrosion fatigue design and estimate reliability of TMCP steel using as the material of heavy industries and plants, its corrosion susceptibilities, corrosion fatigue strength, and determination of fatigue design criterion considering corrosion degradation were investigated. From the results, the corrosion characteristic of TMCP steel is very susceptible in 3.5wt.% NaCl solution. Its susceptibility was linearly increased with the solution temperature increase. The corrosion fatigue strength in $25${\circ}$, 3.5wt.% NaCl solution is very lower than that of in air. And also, it was decreased with the frequency decrease in the same environment. It is expected that the developed corrosion fatigue design method for TMCP steel is useful. However, it is necessary to verify its reliability for actual application.

• Journal of Power System Engineering
• /
• v.9 no.1
• /
• pp.50-56
• /
• 2005

The corrosion experiment was performed for 120 hours on the specimens in the natural seawater tank with four steps of the loaded torsional stress. The surface corrosion pattern of SCM440 area was showed global corrosion and narrow pitting, that was cause by galvanic corrosion between friction welded IN713LC and SCM440. But corrosion does not proceeded from IN713LC area. Initially, the average relative electrode potential and corrosion current were decreased suddenly, by and large, it was stabilized gradually tend to decreasing with the elapse of the immersion time. The corrosion rate was decreased by increasing the load stress, but 200 MPa specimen was showed most large value.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.24 no.6
• /
• pp.171-179
• /
• 2020

In this study, a local corrosion environment monitoring was conducted using steel box specimen fabricated to be the same as actual steel bridge members. The steel box specimen that obtained the same corrosion environment as a steel bridge was classified into the upper plate, bottom plate and web plate. Atmospheric corrosion monitoring sensors(ACM sensors) were installed in each corrosion monitoring member of a steel box specimen to measure the corrosion current and examine time of wetness for each monitoring member. The time of wetness and accumulated corrosion current of each monitoring member were calculated from the measured corrosion current using ACM sensors. The corrosion environment that appeared for each of the steel box members was evaluated from monitoring corrosion environment data as the corrosion current, time of wetness, mean corrosion depth of each monitoring member. Additionally, the atmospheric corrosion environment monitoring was also conducted to compare with the local corrosion environment of steel box members. From these local corrosion environment monitoring for the steel box specimen, the relationship between the relative corrosion environment and mean corrosion depth of each steel box member was examined.