• Corrosion Science and Technology
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• v.21 no.6
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• pp.423-433
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• 2022

The objective of this study was to determine whether Cymbopogon citratus extract as a corrosion inhibitor from natural tropical resources could prevent corrosion of carbon steel in sulfuric acid solution. Inhibitory action of this extract was investigated using electrochemical methods such as potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Those methods revealed corrosion rate, efficiency of inhibition, and adsorptions isotherm values when the extract was added to the sulfuric acid solution at concentration up to 500 ppm with various immersion time at ambient temperature. Results revealed that higher concentration of the extract and longer immersion time decreased the corrosion rate of carbon steel whereas the inhibition efficiency of the extract was increased up to 97.25%. The value of charge transfer resistance was increased significantly by adding the extract at concentration up to 500 ppm with an immersion time of 60 minutes. The type of the extract was a mixed inhibitor. It could inhibit the corrosion process in both anodic and cathodic sides electrochemically. Results of this study suggest that the mechanism of adsorption on the surface of carbon steel is related to Langmuir adsorption isotherm.

• Corrosion Science and Technology
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• v.22 no.3
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• pp.137-152
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• 2023

Polarization behavior and corrosion inhibition of copper in acidic chloride solutions containing benzotriazole were studied. Pourbaix diagrams constructed for copper in NaCl solutions with different BTAH concentrations were used to understand the polarization behavior. Open circuit potential (OCP) depended not only on chloride concentration, but also on whether a CuBTA layer was formed on the copper surface. Only when the (pH, OCP) was located well in the CuBTA region of the Pourbaix diagram, a stable corrosion inhibiting CuBTA layer was formed, which was confirmed by X-ray Photoelectron Spectroscopy (XPS) and a long-term corrosion test. The OCP for the CuBTA layer decreased logarithmically with increasing [Cl^-] activity in the solution. A minimum BTAH concentration required to form a CuBTA layer for a given NaCl concentration and pH were determined from the Pourbaix diagram. It was found that 320 ppm BTAH solution could be used to form a corrosion-inhibiting CuBTA layer inside the corrosion pit in the sprinkler copper tube, successfully reducing water leakage rate of copper tubes. These experimental results could be used to estimate water chemistry inside a corrosion pit.

• Corrosion Science and Technology
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• v.23 no.1
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• pp.20-32
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• 2024

Metal corrosion in acidic environments is a major issue in various industrial applications. This study evaluates the 4-piperonylideneaminoantipyrine (PPDAA) corrosion inhibition efficiency for mild steel in a hydrochloric acid (HCl) solution. The weight loss method was used to determine the corrosion inhibition efficiency at different concentrations and immersion time periods. Results revealed that the highest inhibition efficiency (94.3%) was achieved at 5 mM concentration after 5 hours of immersion time. To inspect the surface morphology of the inhibitor film on the mild steel surface, scanning electron microscopy (SEM) was used before and after immersion in 1.0 M HCl. Density functional theory (DFT) calculations were performed to investigate the molecular structure and electronic properties of the inhibitor molecule to understand the corrosion inhibition mechanism. Theoretical results showed that the inhibitor molecule can adsorb onto the mild steel surface through its nitrogen and oxygen atoms, forming a protective layer that prevents HCl corrosive attack. These findings highlight the potential of PPDAA as an effective corrosion inhibitor for mild steel in HCl solution. Moreover, combining experimental and theoretical approaches provides insights into the mechanism of corrosion inhibition, which is essential for developing effective strategies to prevent metal corrosion in acidic environments.

• Journal of Korea Foundry Society
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• v.35 no.5
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• pp.109-113
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• 2015

In this study, the measurement of FN (ferrite volume fraction) and the solution annealing ratio at a temperature of $1130^{\circ}C$ were determined with 15A elbow fittings of shell cast SSC13, and the corrosion resistance with and without austenitizing solution annealing were investigated in comparison with AISI304. The delta ferrite phase was observed in the material due to the slow cooling effect of the shell mold casting. However, the delta ferrite phase decreased gradually with the solution annealing at a temperature of $1130^{\circ}C$. The hardness generally decreased with a heat treatment; however, its corrosion resistance was improved with the heat treatment. In addition, when a passivation treatment was applied, its corrosion ratio showed the lowest value. The pattern of general corrosion decreased due to the decrease in the delta ferrite phase with the solution annealing treatment. Consequently, it is suggested that the corrosion resistance of SSC13 elbow fittings can be improved by increasing the ratio of any solution annealing treatment used and by decreasing the ferrite phase. The relationship between the ratio of solution annealing and delta ferrite is expressed as follows: SA (solution annealing ratio,%) = 98 - FN (ferrite volume fraction, %).

• Restorative Dentistry and Endodontics
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• v.23 no.1
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• pp.502-514
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• 1998

The purpose of this study is to observe the corrosion characteristcs of four dental amalgams(CAULK FINE CUT, CAULK SPHERICAL, DISPERSALLOY, TYTIN) and to determine a function of chloride concentration through the anodic polarization curve obtained by using a potentiostat. After each amalgam alloy and Hg being triturated, the triturated mass was inserted into the cylinderical metal mold, and condensed by hydrolic pressure. Each specimen was removed from the metal mold. 24 hours after condensation, specimens were polished with the emery paper and stored at room temperature for 6 months. The anodic polarization curves were employed to compare the corrosion behaviours of the amalgam m KCl and KCl-NaCl solution, which had chlonde concentration of 0.4 g/l, 0.8 g/l, 1.2 gil, and 1.6 gil at $37^{\circ}C$ with 3-electrode potentiostat. After the immersion of specimen in electrolyte for 1 hour, the potential scan was begun. The potential scan range was - 1500mV ~+800mV(vs. S.C.E.) in the working electrode and the scan rate was 50mV/sec. The results were as follows, 1. The corrosion potential. the potential of anodic current peak, and transpassive potential in the solution of high chloride concentration shifted to more cathodic direction than those in the solution of low concentration, and the current density in the solution of high chloride concentration was higher than that in the solution of low concentration. 2. The corrosion potential, the potential of anodic current peak, and transpassive potential for CAULK FINE CUT amalgam were the most cathodic among the others, and the current density were the highest among the others. 3. In the solution of low chloride concentration, the corrosion potential, the potential of anodic current peak, and transpassive potential for DISPERSALLOY were the most anodic among the others, however in the solution of high chloride concentration, those for TYTIN were the most anodic among the others. 4. The anodic polarization curve for CAULK SPHERICAL was similar to that for high copper amalgams.

• Corrosion Science and Technology
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• v.12 no.1
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• pp.12-26
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• 2013

This work focused on galvanic corrosion of carbon steel bolted GECM/Al plates by long-term test in tap water and NaCl solutions. Test product was carbon steel bolted between cross packed GECM and painted aluminium. Tests for the product and coupled parts determined corrosion rate in tap water and NaCl solutions. Also, using a potentiostat and salt water sprayer, galvanic test was done. In galvanic test on carbon steel bolted GECM/Al plates, corrosion of carbon steel bolt was faster in series of tap water>1% NaCl solution>3.5% NaCl solution. In galvanic couple between aluminium and carbon steel bolt, their corrosion rates were higher than those of single specimen. In galvanic couple between GECM, aluminium, and carbon steel bolt, corrosion behaviors of carbon steel bolt and aluminium were changed due to different corrosion mechanism in tap water and chloride solution.

• Proceedings of the KSR Conference
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• 2004.06a
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• pp.171-176
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• 2004

Electro chemical corrosion tests were conducted on two structural steels, SS400 and SM490A, in various solutions with different pH values, All materials showed typical active corrosion behaviors in the solutions, and corrosion potential and current density were measured from the slopes obtained from the Tafel curves using linear polarization method. Corrosion potential increased in the acidic region and then decreased depending on the pH values of the solutions. All materials showed the fast corrosion rate in artificial acid rain(pH=4.7), but the slower corrosion rate was observed in NaOH solution(pH=12.0) for SS400 and in distilled water(pH=7.0) for SM490A, respectively, which is thought to come from the difference in chemical composition of two alloys. Generally homogeneous corrosion occurred in acid rain condition, and almost no corrosion was observed in distilled water in both alloys. NaOH solution produced more corrosion than distilled water, and more corrosion had progressed in SS400 than in SM490A in $3.5\%$ NaCl solution.

• Tribology and Lubricants
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• v.20 no.2
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• pp.97-101
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• 2004

This paper reports the studies on the wear-corrosion behavior of Al-Mg alloy in various pH environments. In various pH of sea water, corrosion and wear-corrosion loss of Al-Mg alloy were investigated. Also, the polarization test of Al-Mg alloy using potentiostat/galvanostat was carried out. And the rubbed surface of Al-Mg alloy using scanning electron micrographs after wear-corrosion test was examined in various pH values of sea water. The main results are as following : The polarization resistance of Al-Mg alloy in pH 4 solution is higer than that in pH 6.7 solution, and the corrosion current density in pH 4 is controlled than in pH 6.7 solution. The wear-corrosion loss of Al-Mg alloy with lowering pH becomes sensitive. As the oxide product of Al-Mg alloy appears granular structure and exholiation phenomenon, wear-corrosion loss of Al-Mg alloy increases.

• Corrosion Science and Technology
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• v.16 no.3
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• pp.109-114
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• 2017

Monitoring of corrosion is in most cases based on simulation of environmental conditions on a large and complex structure such as a buried pipeline using a small probe, and the measurement of thermodynamics and kinetics of corrosion processes occurring on the probe surface. This paper presents a hybrid corrosion monitoring probe designed for simulating deteriorating conditions wrought by disbonded coatings and for measuring current densities and distribution of such densities on a simulated pipeline surface. The concept of the probe was experimentally evaluated using immersion tests under cathodic protection (CP) in high resistivity aqueous solution. Underneath the disbonded area, anodic currents and cathodic currents were carefully measured. Anodic current densities were used to calculate metal loss according to Faraday's law. Calculated corrosion patterns were compared with corrosion damage observed at the surface of the probe after a series of stringent tests. The capability of the probe to measure anodic current densities under CP, without requiring interruption, was demonstrated in high resistivity aqueous solution. The pattern of calculated metal loss correlated well with corrosion products distribution observed at the array surface. Working principles of the probe are explained in terms of electrochemistry.

• Corrosion Science and Technology
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• v.16 no.1
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• pp.8-14
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• 2017

The corrosion behavior of a ferritic/martensitic steel T91 exposed to an aqueous solution containing chloride and sulfate ions is investigated depending on the stimulated all-volatile treatment (AVT) and under oxygenated treatment (OT) conditions. The corrosion of T91 steel under OT condition is severe, while the corrosion under AVT condition is not. The co-existence of chloride and sulfate ions has antagonistic effect on the corrosion of T91 steel in both AVT and OT conditions. Unlike to corrosion resistance in the aqueous solution, OT pretreatment provides T91 steel lower oxidation-resistance than VAT pretreatment. From scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS) and X-ray diffraction (XRD) analysis, the lower corrosion resistance in the aqueous solution by VAT conditions possibly is due to the formation of pits. In addition, the lower oxidation resistance of T91 steel pretreated by OT conditions is explained as follows: the cracks formed during the immersion under OT conditions accelerated peeling-off rate of the oxide film.