Method for Mitigating Stray Current Corrosion in Buried Pipelines Using Calcareous Deposits.

Stray current corrosion in buried pipelines can cause serious material damage in a short period of time. However, the available methods for mitigating stray current corrosion are still insufficient. In this study, as a countermeasure against stray current corrosion, calcareous depositions were applied to reduce the total amount of current flowing into pipelines and to prevent corrosion. This study examined the reduction of stray current corrosion via the formation of calcareous deposit layers, composed of Ca, Mg, and mixed Ca and Mg, at the current inflow area. To verify the deposited layers, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) were performed. The electrochemical tests revealed that all three types of calcareous deposits were able to effectively act as current barriers, and that they decreased the inflow current at the cathodic site. Among the deposits, the CaCO3 layer mitigated the stray current most effectively, as it was not affected by Mg(OH)2, which interferes with the growth of CaCO3. The calcium-based layer was very thick and dense, and it effectively blocked the inflowing stray current, compared with the other layers.

Effect of Imidazole as Corrosion Inhibitor on Carbon Steel Weldment in District Heating Water.

Many research studies have been conducted on the corrosion inhibition performance of imidazole in acidic environments such as in the piping of a petrochemical plant. However, there has been no study on the effect of imidazole in alkaline conditions such as a local district water heating environment. Therefore, in this study, the effect of imidazole as a corrosion inhibitor on carbon steel weldment was investigated in alkaline district heating water. Inhibition efficiency and electrochemical properties were investigated by potentiodynamic polarization test and electrochemical impedance spectroscopy. As the concentration of imidazole increased up to 500 ppm, inhibition efficiency increased up to 91.7%. At 1000 ppm, inhibition efficiency decreased. Atomic force microscopy showed that surface coverage of imidazole at 1000 ppm is lower than that of imidazole at 500 ppm. X-ray photoelectron spectroscopy showed that with 500 ppm of imidazole, the amount of pyrrole type interaction is 4.8 times larger than pyridine type interaction. At 1000 ppm of imidazole, the amount of pyridine type interaction is 3.49 times larger than pyrrole type interaction. Depending on the concentration of imidazole, the ratio of interaction between carbon steel and imidazole affected inhibition efficiency.

Effect of Benzotriazole on the Localized Corrosion of Copper Covered with Carbonaceous Residue.

Carbonaceous residues on copper pipes during the manufacturing process are known to be one of the main causes of pitting corrosion on copper pipes. This study examined the corrosion-inhibiting effect of benzotriazole (BTA) on C12200 copper pipes with carbonaceous film in synthetic tap water. In the absence of BTA, localized corrosion mechanisms due to galvanic corrosion, crevice corrosion, and oxygen-concentration cell were proposed in the boundary part of the carbonaceous film on the copper through X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) with energy dispersive spectrometer (EDS) analyses. Electrochemical tests showed that BTA inhibits corrosion by forming Cu-BTA complexes on all over the copper surface where carbonaceous film is present. BTA mitigates galvanic corrosion and crevice corrosion at the boundary of the carbonaceous film and suppresses the formation of oxygen-concentration cells through the formation of a Cu-BTA complex.

Highly Sensitive Electrochemical Aptasensor for Detecting the VEGF165 Tumor Marker with PANI/CNT Nanocomposites.

Sensing targeted tumor markers with high sensitivity provides vital information for the fast diagnosis and treatment of cancer patients. A vascular endothelial growth factor (VEGF165) have recently emerged as a promising biomarker of tumor cells. The electrochemical aptasensor is a promising tool for detecting VEGF165 because of its advantages such as a low cost and quantitative analysis. To produce a sensitive and stable sensor electrode, nanocomposites based on polyaniline (PANI) and carbon nanotube (CNT) have potential, as they provide for easy fabrication, simple synthesis, have a large surface area, and are suitable in biological environments. Here, a label-free electrochemical aptasensor based on nanocomposites of CNT and PANI was prepared for detecting VEGF165 as a tumor marker. The nanocomposite was assembled with immobilized VEGF165 aptamer as a highly sensitive VEGF165 sensor. It exhibited stable and wide linear detection ranges from 0.5 pg/mL to 1 µg/mL, with a limit of detection of 0.4 pg/mL because of the complementary effect of PANI/CNT. The fabricated aptasensor also exhibited good stability in biological conditions, selectivity, and reproducibility after several measurement times after the dissociation process. Thus, it could be applied for the non-invasive determination of VEGF, in biological fluid diagnosis kits, or in an aptamer-based biosensor platform in the near future.

Calibrating the Impressed Anodic Current Density for Accelerated Galvanostatic Testing to Simulate the Long-Term Corrosion Behavior of Buried Pipeline.

Various studies have been conducted to better understand the long-term corrosion mechanism for steels in a soil environment. Here, electrochemical acceleration methods present the most efficient way to simulate long-term corrosion. Among the various methods, galvanostatic testing allows for accelerating the surface corrosion reactions through controlling the impressed anodic current density. However, a large deviation from the equilibrium state can induce different corrosion mechanisms to those in actual service. Therefore, applying a suitable anodic current density is important for shortening the test times and maintaining the stable dissolution of steel. In this paper, to calibrate the anodic current density, galvanostatic tests were performed at four different levels of anodic current density and time to accelerate a one-year corrosion reaction of pipeline steel. To validate the appropriate anodic current density, analysis of the potential vs. time curves, thermodynamic analysis, and analysis of the specimen's cross-sections and products were conducted using a validation algorithm. The results indicated that 0.96 mA/cm2 was the optimal impressed anodic current density in terms of a suitable polarized potential, uniform corrosion, and a valid corrosion product among the evaluated conditions.

Optimizing the Required Cathodic Protection Current for Pre-Buried Pipelines Using Electrochemical Acceleration Methods.

Several corrosion mitigation methods are generally applied to pipelines exposed to corrosive environments. However, in the case of pre-buried pipelines, the only option for corrosion inhibition is cathodic protection (CP). To apply CP, the required current should be defined even though the pipeline is covered with various oxide layers. In this study, an electrochemical acceleration test was used to investigate the synthetic soil corrosion of a pre-buried pipeline. Potentiodynamic polarization experiments were first conducted to ascertain the corrosion current density in the environment, and galvanostatic measurements were performed to accelerate corrosion according to the operating time. In addition, corrosion current density and the properties of the rust layer were investigated via potentiodynamic polarization tests and electrochemical impedance spectroscopy (EIS) tests. The variation in surface corrosion was subsequently analyzed via optical microscopy (OM) and X-ray diffraction (XRD) measurements. Finally, an empirical equation for the optimized CP current requirement, according to the pipeline service time, was derived. This equation can be applied to any corroded pipeline.

Optimization of Cathodic Protection Design for Pre-Insulated Pipeline in District Heating System Using Computational Simulation.

Cathodic protection (CP) has been used as a primary method in the control of corrosion, therefore it is regarded as the most effective way for protecting buried pipelines. However, it is difficult to apply CP to a pipeline for district heating distribution systems, because the pipeline has thermally insulated coatings which could disturb the CP. Theoretical calculation and field tests alone are not enough for a reliable CP design, and therefore additional CP design methods such as computational analysis should be used. In this study, the CP design for pre-insulated pipelines is tested considering several environmental factors, such as temperature and coating defect ratio. Additionally, computational analysis is performed to verify and optimize the CP design. The simulation results based on theoretical methods alone failed to satisfy the CP criteria. Then, a re-design is conducted considering the IR drop. Consequently, all of the simulation results of defective pipelines satisfied the CP criteria after adding the proper CP current.

The comparison on changes of the body heats in electroacupuncture analgesia and anesthesia by ketamine hydrochloride in dogs.

This study was performed to clarify the differences of the body heats between electroacupuncture analgesia (EA) and anesthesia by ketamine hydrochloride (ketamine anesthesia) in dogs. Nine clinically healthy dogs were divided into ketamine anesthesia (control: 5 heads) and EA (experimental: 4 heads) groups, respectively. The acupoints GV-5 and Bai-Hui were used. The infrared thermographic system was used to determine the body heats. The body heats was determined at areas such as the dorsocranial (DCr), dorsocaudal (DCd), ventrocranial (VCr) and ventrocaudal (VCd) regions, on pretreatment, 10, 20, 30, 50 and 90 minutes after treatments, respectively in control and experimental groups. The body heats showed decreasing tendency until 30 minutes after ketamine injection, and then showed increasing pattern until 90 minutes after at all areas investigated in the control group. However, no significant differences of the body heats in the DCr, DCd, VCr and VCd regions were found in the control group. On the other hand, the body heats showed increasing tendency until 30 minutes, and then showed decreasing pattern until 90 minutes after EA, in the experimental group. The significant difference was observed at 30 minutes in the DCr region, and also at 10, 20 and 30 minutes in the DCd regions in the experimental group (p < 0.05). The significant differences of the body heats were detected at 20 minutes in the DCr region, at 30 minutes in the DCd region and at 30 minutes in the VCd region between the experimental and control groups (p < 0.05). In conclusion, EA increases of the body heat in the contrary to that of ketamine anesthesia.