• Journal of Advanced Marine Engineering and Technology
• /
• v.24 no.6
• /
• pp.78-88
• /
• 2000

The effect of post-weld heat treatment(PWHT) of SCM440 steel was investigated with parameters such as micro-Vickers hardness, corrosion potential, polarization behaviors, galvanic current, Al anode generating current and Al anode weight loss, etc. Each hardness of three parts(HAZ, BM, WM) by PWHT is lower than each of as-welded parts. However, hardness of WM area was the highest among those three parts in case of both PWHT and as-welded. Corrosion potential of WM part was the highest among those three parts and WM area was also acted as cathode without regard to PWHT. The magnitude of corrosion potential difference among three parts by PWHT was larger than that of three parts of as-welded, and corrosion current by galvanic cell of these three parts by PWHT was also larger compared to as-welded. Therefore, it is suggested that corrosion resistance property of SCM440 steel is decreased by PWHT than as-welded. However, both Al anode generating current and anode weight loss were also increased by PWHT compared to as-welded when SCM400 steel is cathodically protected by Al anode.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.4 no.3
• /
• pp.161-168
• /
• 2000

A series of in-situ inspection and measurements have been conducted to estimate rebar corrosion incidence of concrete bridges in Seoul metropolitan area. The objectives of this study were to obtain the fundamental data to analysis the causes of rebar corrosion and to establish the repair strategies of deteriorated concrete bridges due to corrosion. The results of this study had been analysed to identify the extent of chloride content and incidence of rebar corrosion by construction ages and by members. After measuring chloride content in concrete, it was concluded that about 76% of all tests on samples from concrete exceed the maximum acceptable limit to risk of chloride-induced corrosion. On the whole, slabs had the most highly chloride content. About 16% of the concrete bridges had a value lower than -350mV (vs. CSE), so it could concluded that the excessive chloride content and carbonation were a major causes of rebar corrosion. Concrete member which carbonation depth penetrates toward rebar was 39% among all tests on samples. The major causes of rebar corrosion were highly chloride content 50%, concrete carbonation 38%, poorly visual condition 6% and etc, 6%.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2003.05a
• /
• pp.39-43
• /
• 2003

Chloride ions are considered to be the major cause of steel corrosion in concrete structures exposed to seashore environments and also permeation of chloride is controlled by chloride diffusion. Therefore, the study on chloride diffusion of concrete have been done so far by many researchers. It is reported that coating material as surface covering material is effect about deterioration of salt damage and carbonation, therefore these materials are important in durability of concrete structure. In this study, corrosion characteristics of reinforcement concrete according to types of surface covering material were evaluated by water-cement ratio, chloride penetration by age on the corrosion area rate and mass decrement of reinforcement. And it is considered that the result of this study on application of the corrosion characteristics of reinforcements under salt damage environmental will be suggested as fundamental data of control performance of salt damage. It is performed that comparison and examination of control performance of salt damage by the corrosion characteristics under salt damage environmental.

• Corrosion Science and Technology
• /
• v.11 no.1
• /
• pp.20-28
• /
• 2012

Since buried pipes contact the soil directly, corrosion by the soil could be occurred. Recently, some stainless steel pipes after 8 years burial at G area were corroded and leaked. In order to elucidate highly corroded phenomena(its rate was about 0.175 mm/y) of these pipes, the investigation for corrosion environment, soil, stray current's effect, and chemical analysis on the pipes were performed. Most of investigated sites were close to traditional water-closet and showed high moisture and thus those areas could be highly corrosive. In the investigation by two kinds of soil evaluation methods, it was revealed that the soils at G areas were highly corrosive, and moreover the contents of sulfate reducing bacteria in the soils were high. Also, open circuit potentials of many pipes showed different values and its potentials were high positive. Therefore, it was considered that corrosion of buried pipes at G area could be affected by high corrosive soil's environment and stray current corrosion.

• Corrosion Science and Technology
• /
• v.19 no.6
• /
• pp.310-317
• /
• 2020

This study investigated the damage to the specimen due to liquid droplet impingement erosion corrosion, which improved the corrosion resistance and durability via hard anodization of 5083-H321 aluminum alloy, which is widely used for small ships and marine structures. The experiment combined liquid droplet impingement erosion and electrochemical equipment with the flow rates in natural seawater solution. Subsequently, Tafel extrapolation of polarization curves was performed to evaluate damage due to the liquid droplet impingement erosion corrosion. The damaged surface was observed using a 3D microscope and a scanning electron microscope. The degree of pitting damage was measured using the Image J program, and the surface hardness was measured using the micro-Vickers hardness tester. The corrosion current density, area, depth, and ratio of the damaged areas increased with the increase in flow rate. The grain size of the damaged area at a flow rate of 20 m s-1 showed fewer and minor differences in height, and a smooth curved shape. The hardness of the damaged surface tended to decrease with increase in flow rate.

• Corrosion Science and Technology
• /
• v.22 no.1
• /
• pp.55-63
• /
• 2023

The aim of this study was to propose a multiple linear regression (MLR) equation to predict ultimate tensile strength (UTS) of 316L stainless steel with unspecified pit corrosion. Tensile specimens with pit corrosion were prepared using a potentiostatic acceleration test method. Pit corrosion was characterized by measuring ten factors using a confocal laser microscope. Data were collected from 22 tensile tests. At 85% confidence level, total pit volume, maximum pit depth, mean ratio of surface area, and mean area were significant factors showing linear relationships with UTS. The MLR equation using these three significant factors at a 85% confidence level showed considerable prediction performance for UTS. Determination coefficient (R²) was 0.903 with training and test data sets. The yield strength ratio of 316L stainless steel was found to be around 0.85. All specimens with a pit corrosion presented a yield ratio of approximately 0.85 with R² of 0.998. Therefore, pit corrosion did not affect the yield ratio.

• International Journal of Concrete Structures and Materials
• /
• v.18 no.1E
• /
• pp.17-22
• /
• 2006

Artificial cracks were made in the cover concrete of specimens embedding ten types of steel rebars of different Cr contents. The research aims for developing Cr-bearing steel rebars resistant to macrocell corrosion environments induced by cracking in cover concrete. The cracks were subjected to intensive penetration of carbon dioxide (carbonation specimens) to form macrocells. The carbonation specimens were then treated with accelerated corrosion curing, during which current macrocell corrosion density was measured. The corrosion area and loss from corrosion were also measured at the end of 105 cycles of this accelerated curing. The results of the study showed that Cr-bearing steel with Cr content of 5% or more suppressed corrosion in a macrocell corrosion environment induced by the differences in the pH values due to carbonation of cracked parts. Cr-bearing steels with Cr content of 7% or more are proven to possess excellent corrosion resistance.

• Journal of the Korean Society for Railway
• /
• v.5 no.1
• /
• pp.32-39
• /
• 2002

As most railways are gradually electrified with modernized electric cars, the demand for catenary wires and their facilities are also increased. Catenary Wires are exposed to the marine area with air-borne salt or severely polluted industrial area with much corrosive emission gases depending on the locations. Corrosion of catenaty wires can make their actual lifetime shorter than that originally designed. Thus, the messenger and ACSR wires, kinds of catenary wire system, were investigated with respect to corrosion, which include new and used ones collected at the field. Tensile strengths and elongations appeared to decrease when the wires were exposed to corrosive environments. The amount of decrease was more prominent as environmental conditions became more corrosive. They are also vibrated with some amplitude everytime pentographs touch contact line. The frequent cyclic load on the wire may result in a fatigue damage. Surface damage by corrosion can make fatigue crack initiate with ease. In the present study, the fatigue life of the used wire was measured 50 to 60% compared with that of new one in average.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2002.11a
• /
• pp.87-91
• /
• 2002

This paper investigates the corrosion inhibition and the reduction of hydration heat properties of Ground Granulated Blast-Furnace Slag (GGBFS) added concrete. Since the massive civil structure is vulnerable to the thermal crack by hydration. adiabatic temperature rising tests were performed for water-binder ratios from 43.2% to 47.3%, while replacing 15% to 50% of cement with GGBFS of equal weight. Then, the corrosion protection performance was evaluated using cylindrical specimens embedded with steel reinforcement according to the combination of 3 W/B ratios and 2 levels of chloride ion quantity. The corrosion area of the embedded steel ban was determined using the high pressure steam curing method specified in KS F 2561. The test results showed that the replacement of GGBFS was effective in reducing the hydration heat. The corrosion area of the embedded steel ban decreased as the replacement of GGBFS increased. However, the corrosion area of the steel bar was proportional to the autoclave cycle and the chloride ion quantity. Among the tested specimens, compressive strength, reduction of hydration heat, and corrosion inhibition performance were excellent when 50% of cement was replaced with GGBFS of equal weight.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.13 no.5
• /
• pp.67-75
• /
• 1993

This study was performed for the purpose of estimating steel corrosion and of considering a countermeasure to prevent steel corrosion of concrete structures under the environment of seawater or using seasand. The corrosion of steel was accelerated in artificial seawater with seven kinds of specimen which was embedded steel in mortar. To assume the degree of steel corrosion, soluble chloride content in mortar, $Cl^-$ binding capacity, half cell potential and corrosion area ratio were measured. The results show that corrosion area ratio was correlative with half cell potential and soluble chloride content in mortar.