• Corrosion Science and Technology
• /
• v.7 no.2
• /
• 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.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.15 no.3
• /
• pp.142-154
• /
• 2011

This study predicted the probability of corrosion initiation of reinforced concrete tunnel boxes structures using the Monte Carlo Simulation. For the inner wall and outer wall in the tunnel boxes, exposed to airborne chloride ion and seawater directly respectively, statistical values of parameters like diffusion coefficient D, surface chloride content $C_s$, cover depth c, and the chloride threshold level $C_{lim}$ were examined from experiment or literature review. Their average values accounted for $3.77{\times}10^{-12}m^2/s$, 3.0% by weight of cement, 94.7mm and 45.5mm for outer wall and inner wall, respectively, and 0.69% by weight of cement for D, $C_s$, c, and $C_{lim}$, respectively. With these parametric values, the distribution of chloride contents at rebar with time and the probability of corrosion initiation of the tunnel boxes, inner wall and outer wall, was examined by considering time dependency of chloride transport. From the examination, the histogram of chloride contents at rebar is closer to a gamma distribution, and the mean value increases with time, while the coefficient of variance decreases with time. It was found that the probability of corrosion initiation and the time to corrosion were dependent on the time dependency of chloride transport. Time independent model predicted time to corrosion initiation of inner wall and outer wall as 8 and 12 years, respectively, while 178 and 283 years of time to corrosion was calculated by time dependent model for inner wall and outer wall, respectively. For time independent model, the probability of corrosion at 100 years of exposure for inner wall and outer wall was ranged 59.5 and 95.5%, respectively, while time dependent model indicated 2.9 and 0.2% of the probability corrosion, respectively. Finally, impact of $C_{lim}$, including values specified in current codes, on the probability of corrosion initiation and corrosion free life is discussed.

• Corrosion Science and Technology
• /
• v.10 no.3
• /
• pp.95-100
• /
• 2011

Protective coatings play an important role in the protection of metallic structures against corrosive environment. The main function of anticorrosive coating is to prevent the materials from corrosive agents, such as water, oxygen and ions. In the study, the corrosion protection properties of urethane and epoxy coating systems were evaluated using EIS methods exposed to the corrosion acceleration test such as Norsok M501, Prohesion and hygrothermal cyclic test. AFM analysis of the coating systems was carried out to monitor the change of roughness of coatings. Urethane coating system was more stable than the epoxy coating under given cyclic conditions. Water uptake into the urethane coatings was less than that into the epoxy coating. The urethane coating system showed better corrosion protection than epoxy coating system based on the changes of the impedance modulus at low frequency region with exposure time. Consequently, the corrosion protection properties of the epoxy and urethane coatings was well correspond with their surface roughness changes and water uptakes.

• Corrosion Science and Technology
• /
• v.10 no.3
• /
• pp.87-94
• /
• 2011

The typical corrosion prevention method inside the steel upper box girder in a suspension bridge involves the use of paints. However, in an effort to reduce environmental impact and cost, the suspension portion of the Yeongjong Bridge, Korea utilizes dehumidification systems to control humidity and prevent corrosion inside its box girder. Maintaining a uniform humidity distribution at the proper level inside the box girder is critical to the successful corrosion control. In this study, the humidity and the resultant atmospheric corrosivity inside the box girder of the Yeongjong Bridge was monitored. The corrosion rate of the steel inside the box girder was obtained using thin-film electrical resistance (TFER) corrosion sensors. Time-of-wetness (TOW) measurements and the deposition rates of atmospheric pollutants such as $Cl^{-}$ and $SO_{x}$ were also obtained. Classification of the atmospheric corrosivity inside the box girder was evaluated according to ISO 9223. As a result, no corrosion was found in the upper box girder, indicating that the dehumidification system used in the Yeongjong Bridge is an effective corrosion control method.

• Proceedings of the KIEE Conference
• /
• 2000.11a
• /
• pp.132-135
• /
• 2000

Direct current corrosion have being investigated by lots of scientists but Alternating current corrosion was ignored because the corrosion rate by AC was very small. Recently however, AC corrosion accidents have been reported in many other countries. So the study of AC corrosion is to be necessary in these days. In this paper, several experiments which intentionally imposed the AC or DC to the specimens also imposed AC and DC at the same time was carried out in the laboratory to examine the AC corrosion characteristics and in addition applied the same way in the field. Moreover, while the field investigations of the abnormal corrosion failures. It was the AC that caused one of corrosion failures.

• Corrosion Science and Technology
• /
• v.2 no.5
• /
• pp.233-237
• /
• 2003

Pickling inhibitors can be used to form an adsorbed layer on the metal surface to hinder the discharge of H^+$ and dissolution of metal ions. Nitrogen-containing inhibitors were selected as corrosion inhibitors for mild steel (MS) in pickling acid process. In this study, the addition of inhibitor, the pickling temperatures and the pickling times were the parameters to investigate the effects on the inhibition efficiency (IE) for MS by using weight loss measurement. Preliminary results show that the IE increased with the increase in pickling time from 10 minutes to 60 minutes, and the IE also increased with the increase in temperature at room temperature and $40^{\circ}C$. At the higher temperature. the IE values are higher and almost independent with the pickling time. Furthermore, the potentiodynamic polarization, open circuit corrosion potential-time and corrosion current-time studies show that nitorgen-containing inhibitor behaves predominantly as cathodic polarization. The roughness test and SEM investigation are also studied in this paper.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.21 no.1
• /
• pp.117-125
• /
• 2017

The role of fly ash in concrete become impotent with finding the characteristics of fly ash in which it is used as cement replacement material. In this paper, corrosion test results obtained by two test methods such as the long-term exposure corrosion test and the accelerated corrosion test method, were compared to investigated the corrosion resistance between fly ash concrete and normal concrete. Corrosion initiation time was measured in two types of concrete, i.e., one mixed with fly ash(FA) and the other without admixture(OPC). The accelerated corrosion test was carried out by four case, i.e., two samples is a cyclic drying-wetting method combined without carbonation(case 1) and combined with carbonation(case 2), and the other two samples is a artificial seawater ponding test method combined without carbonation(case 3) and combined with carbonation(case 4). Whether corrosion occurs, it was measures using half-cell potential method. The ponding test combined without carbonation was most effective in accelerating corrosion time of steel bars. The results indicated that the corrosion of rebar embedded in concrete occurred according to the order of OPC, FA. The delay relative ratio of corrosion obtained by corrosion initiation time between FA and OPC is 1.04 to 1.27. Consequently, fly ash concrete as the age increases its corrosion resistance was improved compared with OPC concrete.

• Journal of Ocean Engineering and Technology
• /
• v.19 no.2 s.63
• /
• pp.53-59
• /
• 2005

The effect of pH on the corrosion characteristics in the dissimilar friction welded zone of IN713LC-SCM440 in the loaded torsional stress was studied. The corrosion experiment was performed for 120 hours on the specimens with five steps of pH. The surface corrosion pattern of the SCM440 area showed global corrosion and narrow pitting, which was caused by galvanic corrosion between friction welded IN713LC and SCM440, but corrosion did not proceeded from the IN713LC area. The average relative electrode potential gradually tends to decrease with the elapse of the immersion time in the acidity area. The average corrosion current also gradually tend to decrease The corrosion rate showed a larger value when the average relative electrode potential was higher and the average relative current was lower. The corrosion rate showed a larger value when the average relative electrode potential was higher in the acidity area, and it showed large when the average relative electrode potential was lower in the alkalinity area.

• Corrosion Science and Technology
• /
• v.17 no.5
• /
• pp.231-241
• /
• 2018

Atmospheric corrosion is generally an electrochemical degradation process of metal. It can be caused by various corrosion factors of atmospheric component, weather, and air pollutants. Moisture, particles of sea salts, and sulfur dioxide are major factors in atmospheric corrosion. Galvanizing coating is one of the most efficient ways to protect iron from corrosion by zinc plating on the surface of the iron. Galvanized steels are being widely used in automobiles, building structures, roofing, and other industrial structures due to their high corrosion resistance compared to bare iron. Atmospheric corrosion of galvanized steel has shown complex corrosion behavior depending on coating process, coating thickness, atmospheric environment, and air pollutants. In addition, different types and kinds of corrosion products can be produced depending on the environment. Lifespan of galvanized steels is also affected by the environment. Therefore, the objective of this study was to determine the corrosion behavior of galvanized steel under atmospheric corrosion at six locations in Korea. When the exposure time was increased, content of zinc from GA surface decreased while contents of iron and oxygen tended to increase. On the other hand, content of iron was constant even after 36 months of exposure of GI.

• Corrosion Science and Technology
• /
• v.15 no.1
• /
• pp.18-27
• /
• 2016

In this study, the accelerated corrosion test by combined deteriorating action of salt damage and freeze-thaw was investigated. freeze-thaw cycle is one method for corrosion testing; corrosion initiation time was measured in four types of concrete samples, i.e., two samples mixed with fly ash (FA) and blast furnace slag (BS), and the other two samples having two water/cement ratio (W/C = 0.6, 0.35) without admixture (OPC60 and OPC35). The corrosion of rebar embedded in concrete occurred most quickly at the $30^{th}$ freeze-thaw cycle. Moreover, a corrosion monitoring method with a half-cell potential measurement and relative dynamic elastic modulus derived from resonant frequency measures was conducted simultaneously. The results indicated that the corrosion of rebar occurred when the relative dynamic elastic modulus was less than 60%. Therefore, dynamic elastic modulus can be used to detect corrosion of steel bar. The results of the accelerated corrosion test exhibited significant difference according to corrosion periods combined with each test condition. Consequently, the OPC60 showed the lowest corrosion resistance among the samples.