• 한국물환경학회지
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• 제33권3호
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• pp.359-369
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• 2017

Water distribution systems supply drinking water to consumers' taps. Internal corrosion of metallic pipe used in drinking water distribution systems has reduced water quality and led to increased levels of toxic heavy metals such as lead, copper and nickel. These problems have been experienced to varying degrees by water utilities in many countries. North America has successfully managed and controlled pipe corrosion and corrosive water in water distribution system based on various policies, regulations and rules. Practical and engineering guidelines for evaluation of pipe corrosion and determination of treatment options are also provided to assist drinking water supplies. In addition, the corrosion mechanism in water distribution systems, such as the complex effects of physical and chemical parameters on the corrosion pipes has been improved to accurately predict corrosion rates of metallic pipes in actual water distribution systems. This paper reviews various regulations, policy statement, and treatment produces on controlling corrosion in drinking water distribution systems in US and Canada and then offers suggestion for management of corrosive water and pipe corrosion in drinking water distribution system in Korea.

• Corrosion Science and Technology
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• 제7권6호
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• pp.319-323
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• 2008

The polarization resistance of mild steel in 0.5M hydrochloric acid has been evaluated by using impedance (Z) and linear polarization (LPR) techniques and compared to the noise resistance obtained from electrochemical noise data. The degree of localization of this general corrosion has also been discussed by evaluating localization index and power spectral density. Polarization resistance obtained by LPR technique ($28\Omega$) was higher than that obtained by impedance technique ($15\Omega$). Noise resistance ($11\Omega$) was much lower than polarization resistance measured by both of above techniques. Higher polarization resistance obtained by LPR technique is generally caused by passivation effect in the presence of scales or deposits which can introduce an increased resistance as can low conductivity electrolytes. The reason why noise resistance is lower than polarization resistance is the effect of background noise detected by using three platinum electrodes cell in 0.5M hydrochloric acid. Slope($-\beta$) of power spectral density (PSD) obtained from analysis of noise data ($-\beta$ = 3.3) was much higher than 2 which indicates mild steel corroded uniformly. Localization index (LI) calculated from statistical analysis (LI=0.08) is much lower than 1 which indicates that mild steel did not corroded locally. However, LI value is still higher than $1x10^{-3}$ and this indicates that mild steel corroded locally in microscopic point of view.

• 상하수도학회지
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• 제25권5호
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• pp.731-739
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• 2011

To investigate corrosivity characteristics of tap water in Korea, Langelier index (LI) of 30 multi-regional water treatment plants (WTPs) were evaluated. Weekly LI values of 30 WTPs were all negative, which means tap water in Korea might be very corrosive. Maximum LI decrease through water treatment processes was 0.95 under no additional corrosion control process. Based on the correlation results between LI and tap water qualities, pH and calcium concentration were confirmed as major parameters for LI control. Addition of calcium hydroxide with $CO_{2}$ or calcium hydroxide or sodium hydroxide can be chosen based on water quality. Continuous monitoring of LI and related parameters is recommended in water distribution system.

• 한국재료학회지
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• 제24권1호
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• pp.53-59
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• 2014

The corrosion resistance of submerged entry nozzle (SEN) materials were investigated for high-class steel manufacturing. Composite samples were fabricated by mixing $ZrO_2$, $Al_2O_3$, MgO, mullite, spinel, and carbon. The raw materials were mixed with attrition milling, compacted in a uniaxial pressure of 200MPa and calcined at $1000^{\circ}C$ for 3 h in $N_2$ atmosphere. The bulk density and apparent porosity of the calcined samples were measured by the liquid displacement method in water using Archimedes's principle. The corrosion resistance of the samples were measured by cup test with mold powder at $1550^{\circ}C$ for 2 h. The microstructure and elemental analysis of samples were observed by scanning electron microscopy (SEM), energy dispersive spectrum (EDS), and X-ray diffraction pattern (XRD). The XRD result shows that the starting raw materials were crystalline phase. The microstructure of fabricated specimen was investigated before and after corrosion tests at $1000^{\circ}C$ and $1550^{\circ}C$ for 2h. $ZrO_2$-C composite showed good resistance in the slag corrosion test. Among the composite oxide materials, $ZrO_2-Al_2O_3$-C and $ZrO_2$-MgO-C showed better resistance than $ZrO_2$-C in the slag corrosion test. The diameter variation index of $ZrO_2$-C refractory was 16.1 at $1000^{\circ}C$ for 2 h. The diameter variation index of the $ZrO_2-Al_2O_3$-C refractory was larger than that of the $ZrO_2$-C refractory at $1550^{\circ}C$ for 2 h.

• Earthquakes and Structures
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• 제9권4호
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• pp.851-873
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• 2015

A methodology for estimation of statistical properties (viz. mean and standard deviation) of the expected seismic damage to reinforced concrete framed structures subject to corrosion of reinforcement, over a specified reference time (typically the service life of the structure) is proposed in this paper. The damage to the structure under the earthquake loading is characterised by the damage index, determined using the modified Park and Ang damage model. The reduction in area, yield strength and strain at ultimate of steel reinforcement, and the reduction in compressive strength of cover concrete due to corrosion are taken into account in the estimation of damage. The proposed methodology is illustrated through an example problem. From the results obtained, it is noted that there is an increase of about 70% in the mean value of expected seismic damage to the reinforced concrete frame considered over a reference time of 30 years when effect of corrosion is taken into consideration. This indicates that there is a need to consider the effect of corrosion of reinforcement on the estimation of expected seismic damage.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2009년도 춘계학술대회 논문집
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• pp.1105-1106
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• 2009

• Computers and Concrete
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• 제31권3호
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• pp.241-252
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• 2023

Corrosion of rebar is one of the major deteriorating mechanisms that affect the durability of reinforced concrete (RC) structures. The increase in CO₂ concentration in the atmosphere leads to early carbonation and deterioration due to corrosion in RC structures. In the present study, an attempt has been made to modify the existing carbonation depth prediction empirical model. The modified empirical model is verified from the carbonation data collected from selected RC structures of CSIR-SERC campus, Chennai and carbonation data available from the reported literature on in-situ RC structures. Attempt also made to study the carbonation depth in the laboratory specimens using oxygen permeability index (OPI) test. The carbonation depth measured from RC structures and laboratory specimens are compared with estimated carbonation depth obtained from OPI test data. The modified empirical model shows good correlation with measured carbonation depth from the identified RC structures and the reported RC structures from the literature. The carbonation depth estimated from OPI values for both in-situ and laboratory specimens show lesser percentage of error compared to measured carbonation depth. From the present investigation it can be said that the OPI test is the suitable test method for both new and existing RC structures and laboratory RC specimens.

• 콘크리트학회논문집
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• 제19권3호
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• pp.385-389
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• 2007

In this study, it was investigated the resistance of OPC, 60% GGBS, 20% PFA and 10% SF mortar specimens against sulfuric acid corrosion. As an index for degree of acid corrosion, the corrosion depth was evaluated. Then, it was found that an increase in the duration of immersion and a decrease in the pH, as expected, resulted in a more severe corrosion irrespective of binders; 60% GGBS mortar specimen was the most resistant to sulfuric acid corrosion. From the laboratory testing of sulfuric acid corrosion, an empirical prediction model was suggested as a power function of time and the pH of sulfuric acid, and was applied to an assessment of concrete structures exposed to an acidic environment. It was found that the empirical model gave a more precise prediction of sulfuric acid deterioration of concrete rather than a conventional model, mostly used for predicting carbonation of concrete.

• 상하수도학회지
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• 제30권5호
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• pp.579-586
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• 2016

In many countries in order to manage corrosion of water treatment process, it is currently using Langelier index (LI). However, management of the Larson's ratio (LR) to compare corrosion management and LI which can be generated by the water treatment process is required. In this study, in order to ensure data LR, factors associated with the actual corrosion resistance of water treatment plant was measured. Using the measured data, the model equation can be estimated alkalinity, and using the statutory water quality data, LR and alkalinity is estimated. At comparison of the measured value and estimated value of alkalinity, it appeared in $R^2$ = 0.629, using the statutory water quality data and estimated alkalinity model, LR and alkalinity (Whole water treatment plants : 472) is estimated. Concentration of estimated alkalinity is 0.5 mg/L to 107.5 mg/L (average : 23.2 mg/L), and LR is 0.1 to 10 (average : 1.3). At tendency to corrosion of investigated LR, "No metal tendency" (>0.5) is 39 water treatment plants, 8.26 %, and "corrosion metal tendency" is 433 water treatment plants, 91.74%.

• Journal of Welding and Joining
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• 제4권3호
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• pp.58-71
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• 1986

Mechanical and corrosion property of duplex stainless steel weldments made by the GTAW and SMAW process were studied. Fracture toughness, general and local corrosion resistance of GTAW and SMAW weldments were evaluated in terms of Charpy V notch impact test, anodic polarization diagram, pitting corrosion rate, respectively. SMA weld metal showed much lower impact toughness and higher ductile-brittle transition temperature than GTA weld metal. Fractographic and EDX analysis on fracture surface of SMA weld metal demonstrated the existence of (Si, Ti), oxide in large amounts. Potentiodynamic anodic polarization diagram of GMA weld metal showed much lower passive current density than SMA weld metal in 4% $H_2/SO_4$ solution. And pitting corrosion rate test showed the same tendency. Relating the microstructure, chemistry and property, it can be concluded that GTA weld metal gives better toughness due to lower oxygen content, i.e. lower inclusion content, and better corrosion resistance due to higher Pitting Index(PI) than SMA weld metal.