scholarly journals Initial Stages of AZ31B Magnesium Alloy Degradation in Ringer′s Solution: Interpretation of EIS, Mass Loss, Hydrogen Evolution Data and Scanning Electron Microscopy Observations

Metals ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 933 ◽  
Author(s):  
Lucien Veleva ◽  
Mareny Guadalupe Fernández-Olaya ◽  
Sebastián Feliu
Keyword(s):  
Magnesium Alloy ◽  
Hydrogen Evolution ◽  
Electrochemical Impedance ◽  
Corrosion Current ◽  
Charge Transfer Resistance ◽  
Uniform Corrosion ◽  
Transfer Resistance ◽  
Az31b Magnesium Alloy ◽  
Current Densities ◽  
Eis Measurements

The initial stages of corrosion of AZ31B magnesium alloy, immersed in Ringer′s solution at 37 °C body temperature for four days, have been evaluated by independent gravimetric and chemical methods and through electrochemical impedance spectroscopy (EIS) measurements. The corrosion current densities estimated by hydrogen evolution are in good agreement with the time-integrated reciprocal charge transfer resistance values estimated by EIS. The change in the inductive behavior has been correlated with difference in the chemical composition of corrosion layers. At the shorter immersion of 2 days, EDS analysis of cross section of the uniform corrosion layer detected Cl and Al elements, perhaps as formed aluminum oxychlorides salts.

scholarly journals Effect of Cross Rolling on the Corrosion Resistance of AZ31 Magnesium Alloy

2020 ◽  
Vol 71 (8) ◽  
pp. 176-182
Author(s):  
Zhiquan Huang ◽  
Jinchao Zou ◽  
Guowei Yang ◽  
Yanchun Zhu ◽  
Hongyu Lai ◽  
...  
Keyword(s):  
Magnesium Alloy ◽  
Electrochemical Impedance ◽  
Corrosion Current ◽  
Charge Transfer Resistance ◽  
Az31 Magnesium Alloy ◽  
Constant Current ◽  
Transfer Resistance ◽  
Discharge Performance ◽  
Cross Rolling ◽  
Effective Contact

The effect of different rolling methods on the microstructure and corrosion behavior of AZ31 magnesium alloy in a 3.5% NaCl solution was studied via potentiodynamic polarization scanning, constant current discharge and electrochemical impedance spectroscopy. Results show that the corrosion current densities of cross rolling and unidirectional rolling are 8.60�10-3 and 4.68�10-2 A/cm2, respectively. Their difference is 5.4fold, the charge transfer resistance of cross rolling is large, the corrosion of one-way rolling is more serious than that of cross rolling, the discharge performance of cross rolling is more stable, and the anode polarization is small. After cross rolling, the grain size of the plate is relatively uniform and the corrosion products are non-adherent and less, so it is easy to fall off from its surface, which increases the effective contact between the electrolyte and the alloy surface and has more stable discharge performance.

scholarly journals INFLUENCE OF A PREFABRICATED-CROWN ROLLING PROCESS ON THE CORROSION BEHAVIOUR OF AZ31 MAGNESIUM ALLOY

2021 ◽  
Vol 55 (4) ◽  
Author(s):  
Zhiquan Huang ◽  
Jinchao Zou ◽  
Junpeng Wang ◽  
Yanjie Pei ◽  
Renyao Huang ◽  
...  
Keyword(s):  
Magnesium Alloy ◽  
Corrosion Behavior ◽  
Electrochemical Impedance ◽  
Corrosion Behaviour ◽  
Plate Thickness ◽  
Az31 Alloy ◽  
Rolling Process ◽  
Charge Transfer Resistance ◽  
Az31 Magnesium Alloy ◽  
Transfer Resistance

The present study aims to investigate the effect of a prefabricated-crown rolling process on the corrosion characteristic of the AZ31 magnesium alloy. Specimens made of the AZ31 alloy were rolled under various crown conditions, and their microstructure evolution and corrosion behavior were analyzed. The corrosion behavior was studied using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results showed that the corrosion-current density of the AZ31 alloy with a side pressure of 37.5 % of the plate thickness of the precast convexity decreased from 3.79 × 10–6 A/cm2 to 1.80 × 10–6 A/cm2, and the difference between the edge and the middle of the AZ31 alloy was shortened from 2.05 × 10–6 A/cm2 to 1.14 × 10–6 A/cm2. The charge-transfer resistance also increased from 507.1 Ω·cm2 to 581.2 Ω·cm2. The improvement in the corrosion resistance is a result of the more stable corrosion products and microstructure refinement formed after the prefabricated-crown rolling process.

Corrosion performance of mild steel and epoxy coated rebar in concrete under simulated harsh environment

2019 ◽  
Vol 37 (5) ◽  
pp. 657-678
Author(s):  
Muazzam Ghous Sohail ◽  
Mohammad Salih ◽  
Nasser Al Nuaimi ◽  
Ramazan Kahraman
Keyword(s):  
Mild Steel ◽  
Polarization Resistance ◽  
Electrochemical Impedance ◽  
Corrosion Current ◽  
Charge Transfer Resistance ◽  
Harsh Environment ◽  
Corrosion Performance ◽  
Transfer Resistance ◽  
Content Type ◽  
Rc Structures

Purpose The purpose of this paper is to present the results of a two-year long study carried out in order to evaluate the corrosion performance of mild steel bare bars (BB) and epoxy-coated rebar (ECR) in concrete under a simulated harsh environment of chlorides. Design/methodology/approach The blocks are subjected to Southern Exposure testing. The electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR) and Tafel plot are performed to measure the polarization resistance and corrosion current densities of these rebars. Knife-peel test was performed to assess the adhesion between epoxy and underlying steel after two years of exposure. Findings Mild steel BB showed a high corrosion current density of 1.24 µA/ cm2 in Tafel plots and a very low polarization resistance of 4.5 kΩ cm2 in LPR technique, whereas very high charge transfer resistance of 1672 and 1675 kΩ cm2 is observed on ECR and ECR with controlled damage (ECRCD), through EIS technique, respectively. EIS is observed to be a suitable tool to detect the defects in epoxy coatings. After two years of immersion in 3.89 percent NaCl− solution, the mild steel BB were severely corroded and a considerable weight loss was observed, whereas under heavy chloride attack, ECR showed no deterioration of epoxy coating and neither any corrosion of underlying steel. Results of this study show that the durability of reinforced concrete (RC) structures with respect to corrosion could be enhanced by using ECR, especially in harsh climatic conditions. Originality/value The corrosion performance of mild steel and ECR in concrete under a simulating splash zone environment is evaluated. EIS was used to evaluate the health of epoxy and corrosion state of underneath steel rebars. EIS was able to detect the defects in epoxy. The durability of RC structures could be enhanced in harsh climate regions by using ECR.

scholarly journals The Effect of Achyranthes aspera Extracts on Mild Steel Corrosion in Industrial Water Medium

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Chikkur B. Pradeep Kumar ◽  
Kikkeri N. Mohana
Keyword(s):  
Mild Steel ◽  
Electrochemical Impedance ◽  
Electrochemical Techniques ◽  
Steel Corrosion ◽  
Charge Transfer Resistance ◽  
Water Medium ◽  
Industrial Water ◽  
Transfer Resistance ◽  
Achyranthes Aspera ◽  
Eis Measurements

Achyranthes aspera (AA) extracts were studied as corrosion inhibitor for mild steel (MS) in industrial water medium using mass loss and electrochemical techniques. The results of the study revealed that AA extracts inhibit MS corrosion through adsorption process following Langmuir adsorption isotherm model. The protection efficiency increased with increase in inhibitor concentration and decreased with temperature. The electrochemical impedance spectroscopy (EIS) measurements showed that the charge transfer resistance increases with increase in the concentration of AA extracts. The polarization curves obtained indicate that AA extracts act as mixed type of inhibitor. Scanning electron microscopy (SEM) was used to analyze the surface adsorbed film.

Microstructure and Electrode Characteristics of Ti-V-Cu-Cr-Ni Metal Hydride Electrode Alloy

2012 ◽  
Vol 512-515 ◽  
pp. 1933-1936
Author(s):  
Yu Qing Qiao ◽  
Min Shou Zhao ◽  
Li Min Wang
Keyword(s):  
Metal Hydride ◽  
Electrochemical Impedance ◽  
Secondary Phase ◽  
Charge Transfer Resistance ◽  
Solid Solution Phase ◽  
Transfer Resistance ◽  
Metal Hydride Electrode ◽  
Eis Measurements ◽  
Increasing Temperature ◽  
Electrode Characteristics

Microstructure and electrode characteristics of Ti-V-Cu-Cr-Ni metal hydride electrode alloy have been investigated by XRD, FESEM-EDS and EIS measurements. The result shows that the alloy is mainly composed of V-based solid solution phase with body-centered-cubic structure and TiNi-based secondary phase. The discharge capacity increases with increasing temperature in a wider temperature region from 303 K to 343 K. The result of electrochemical impedance spectrometry indicates that the charge transfer resistance decreases with increasing temperature, while the exchange current density in the bulk of the alloy increase with increasing temperature.

Evaluation of corrosion inhibition and adsorption behavior of Thymuszygis subsp. gracilis volatile compounds on mild steel surface in 1 m HCl

2020 ◽  
Vol 38 (2) ◽  
pp. 137-149
Author(s):  
Mohamed Ouknin ◽  
Abderrahmane Romane ◽  
Jean-Pierre Ponthiaux ◽  
Jean Costa ◽  
Lhou Majidi
Keyword(s):  
Mild Steel ◽  
Electrochemical Impedance ◽  
Aggressive Medium ◽  
Three Dimensional ◽  
Steel Corrosion ◽  
Charge Transfer Resistance ◽  
Infrared Analysis ◽  
Transfer Resistance ◽  
3D Profilometry ◽  
Eis Measurements

AbstractThe inhibition effect of Thymus zygis subsp. gracilis (TZ) on mild steel corrosion in 1 m hydrochloric acid has been investigated by weight loss measurements, surface analysis [scanning electron microscopy (SEM)-energy-dispersive X-ray (EDX), three-dimensional (3D) profilometry, and Fourier transform infrared analysis], potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). Gravimetric results indicate that TZ exhibits good inhibition efficiency of 80.40% attained at 3 g/l. Polarization measurements show that the studied inhibitor is a mixed type. EIS measurements revealed that the charge transfer resistance increases with increasing concentration of TZ, which suggests a Langmuir adsorption isotherm model. Based on SEM-EDX and 3D profilometry, it appears that the surface is remarkably improved in the presence of TZ oil compared to that exposed to the acid medium without TZ oil. From the obtained results, it can be concluded that this oil is a new natural substance that can be used against material corrosion in aggressive medium.

Corrosion Analysis of Reinforcing Steels in Mortar for Nuclear Facilities

2009 ◽  
Author(s):  
Toshiyasu Nishimura
Keyword(s):  
Electrochemical Impedance ◽  
Initial Period ◽  
Charge Transfer Resistance ◽  
Ion Concentration ◽  
Reinforcing Steel ◽  
Nuclear Facilities ◽  
Good Correspondence ◽  
Transfer Resistance ◽  
Eis Measurements ◽  
Cover Thickness

It is important to estimate the corrosion of reinforcing steel in mortar facilities, because the nuclear plants are located near the sea side. In the case of environmental factors in mortar, the Cl ion concentration and pH were monitored by inserting microelectrodes into artificial pores in the mortar. At the same time, the corrosion behavior of the reinforcing steel was investigated by EIS (electrochemical impedance spectroscopy). In the EIS measurements of the reinforcing steel, diffusion behavior was confirmed in the initial period, but diffusion could no longer be observed after 35 day. In comparison with a 10mm cover thickness, a 20mm cover thickness showed a higher impedance behavior. The Cl ion concentration in the mortar was obtained using Ag/AgCl microelectrodes, showing that this behavior is generally controlled by diffusion. When the diffusion equation was used in this work, the diffusion coefficient (Dc) showed a high value of Dc = 2×10−4 mm2/sec. Similarly, the pH in the mortar was obtained using W/WOx microelectrodes. With a 20mm cover thickness, pH was limited to approximately pH11, but with a 10mm cover thickness, pH continued to decrease to around pH9.5. The latter phenomenon was considered to be the result of neutralization by penetration of the immersion solution from the surface. Based on the results of monitoring with the microelectrodes, solutions simulating those in the pores in mortar were prepared and used in EIS measurements. The charge transfer resistance Rct in the simulated solutions showed good correspondence with the impedance in the low frequency region (2mHz) in the actual mortar. This is attributed to the fact that the corrosion of reinforcing steel was controlled by the solution conditions (mainly Cl concentration and pH) in the pores in mortar. If these solution conditions (Cl concentration, pH) exceed threshold values, it was found that the passivation film is destroyed, resulting in high corrosion.

Corrosion Resistance of Zn-Al-Mg Alloys with Hypoeutectic Microstructure

2019 ◽  
Vol 298 ◽  
pp. 52-58
Author(s):  
Guang Rui Jiang ◽  
Jian Zhou ◽  
Ting Shang ◽  
Guang Hui Liu
Keyword(s):  
Corrosion Resistance ◽  
Corrosion Potential ◽  
Electrochemical Impedance ◽  
Ternary Eutectic ◽  
Corrosion Current ◽  
Charge Transfer Resistance ◽  
Mg Alloys ◽  
Transfer Resistance ◽  
Warburg Impedance ◽  
Al Mg Alloys

Zn-Al-Mg alloys with hypoeutectic microstructure were melted through a high frequency induction furnace. The content of aluminum and magnesium in the alloys were between 1% to 2%. Scanning electron microscopy (SEM) was utilized to analyze microstructure and phase, respectively. Effect of alloying element contents on corrosion resistance was studied. Results show that the Zn-Al-Mg alloys are almost covered by primarily solidified Zn rich block phase and fine lamellar binary and ternary eutectic microstructure exist between the Zn rich phase. The corrosion resistance was characterized through electrochemical test which indicates that increasing Al and Mg content in the Zn-Al-Mg alloys decline corrosion current density. For alloys with 1% Al, more magnesium means lower corrosion potential. For alloys with 2% Al, however, more magnesium suggests higher corrosion potential. In Nyquist curves of electrochemical impedance spectroscopy (EIS) test, Warburg impedance portion could be found for all alloys. With increasing alloying elements content in the Zn-Al-Mg alloys, charge transfer resistance in higher frequency remarkably increase, which implies higher corrosion resistance.

Effect of Cl- Content, pH Value and CO2 on Electrochemical Corrosion Features of Cr15 Super Martensitic Stainless Steel

2013 ◽  
Vol 738 ◽  
pp. 92-96
Author(s):  
Jin Ming Long ◽  
Quan Bin Liu ◽  
Kun Yu Zhao ◽  
Qi Long Yong ◽  
Jie Su
Keyword(s):  
Stainless Steel ◽  
Martensitic Stainless Steel ◽  
Electrochemical Impedance ◽  
Ph Value ◽  
Charge Transfer Resistance ◽  
Uniform Corrosion ◽  
Nacl Solution ◽  
Transfer Resistance ◽  
Pitting Potential ◽  
Super Martensitic Stainless Steel

The corrosion behavior of a Cr15 super martensitic stainless steel (Cr15 SMSS) was investigated in NaCl solutions by means of potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Effects of Cl-content, pH value and saturated CO2on corrosion were sdudied. It was found that the parameters of maintaining passivity current density (ip), the critical pitting potential (Eb) and charge transfer resistance (Rt) of Cr15 SMSS varied widely under different conditions. The corrosion resistance of Cr15 SMSS decrease with increasing Cl-concentration and lowering pH value. BothipandEbincrease for Cr15 SMSS in CO2-saturated NaCl solution, which verified that the CO2in NaCl solution can result in lower pitting sensitivity and higher uniform corrosion rate to Cr15 SMSS.

scholarly journals Bioleaching and Electrochemical Behavior of Chalcopyrite by a Mixed Culture at Low Temperature

2021 ◽  
Vol 12 ◽  
Author(s):  
Tangjian Peng ◽  
Wanqing Liao ◽  
Jingshu Wang ◽  
Jie Miao ◽  
Yuping Peng ◽  
...  
Keyword(s):  
Low Temperature ◽  
Mixed Culture ◽  
Pure Culture ◽  
High Throughput Sequencing ◽  
Electrochemical Impedance ◽  
Corrosion Current ◽  
Charge Transfer Resistance ◽  
Microbial Consortia ◽  
Cyclic Voltammograms ◽  
Transfer Resistance

Low-temperature biohydrometallurgy is implicated in metal recovery in alpine mining areas, but bioleaching using microbial consortia at temperatures <10°C was scarcely discussed. To this end, a mixed culture was used for chalcopyrite bioleaching at 6°C. The mixed culture resulted in a higher copper leaching rate than the pure culture of Acidithiobacillus ferrivorans strain YL15. High-throughput sequencing technology showed that Acidithiobacillus spp. and Sulfobacillus spp. were the mixed culture’s major lineages. Cyclic voltammograms, potentiodynamic polarization and electrochemical impedance spectroscopy unveiled that the mixed culture enhanced the dissolution reactions, decreased the corrosion potential and increased the corrosion current, and lowered the charge transfer resistance and passivation layer impedance of the chalcopyrite electrode compared with the pure culture. This study revealed the mechanisms via which the mixed culture promoted the chalcopyrite bioleaching.

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