scholarly journals On the corrosion mechanism of Mg investigated by electrochemical impedance spectroscopy

2019 ◽  
Vol 306 ◽  
pp. 61-70 ◽  
Author(s):  
Maurilio Pereira Gomes ◽  
Isolda Costa ◽  
Nadine Pébère ◽  
Jesualdo Luiz Rossi ◽  
Bernard Tribollet ◽  
...  
Keyword(s):  
Electrochemical Impedance Spectroscopy ◽  
Impedance Spectroscopy ◽  
Electrochemical Impedance ◽  
Corrosion Mechanism

scholarly journals Electrochemical Behavior of Conventional and Rheo-High-Pressure Die Cast Low Silicon Aluminum Alloys in NaCl Solutions

CORROSION ◽  
10.5006/3254 ◽  
2019 ◽  
Vol 75 (11) ◽  
pp. 1339-1353
Author(s):  
Maryam Eslami ◽  
Flavio Deflorian ◽  
Caterina Zanella
Keyword(s):  
High Pressure ◽  
Electrochemical Impedance Spectroscopy ◽  
Impedance Spectroscopy ◽  
Electrochemical Behavior ◽  
Anodic Polarization ◽  
Electrochemical Impedance ◽  
Casting Process ◽  
Corrosion Mechanism ◽  
Die Cast ◽  
Polarization Test

The electrochemical behavior of a low silicon aluminum alloy cast by the conventional and rheo-high-pressure die cast processes is evaluated using polarization test and electrochemical impedance spectroscopy in 0.01 M, 0.05 M, 0.1 M, and 0.6 M sodium chloride solutions. Compared to the conventional high-pressure die cast process, rheocasting introduces some alterations in the microstructure including the presence of aluminum grains with different sizes, formed at different solidification stages. According to the results of the anodic polarization test, conventional cast and rheocast samples show similar breakdown potentials. However, the rheocast samples present enhanced oxygen reduction kinetics compared to the conventional cast sample. Based on scanning electron microscopy examinations, localized microgalvanic corrosion is the main corrosion mechanism for both alloys and it initiates at the interface of aluminum with iron-rich intermetallic particles which are located inside the eutectic regions. The corrosion further develops into the eutectic area. Although the rate of the cathodic reaction can be influenced by the semisolid microstructure, according to the results of anodic polarization and electrochemical impedance spectroscopy tests, the corrosion behavior is not meaningfully affected by the casting process.

A Study of Hot Corrosion of Fe-Cr Alloys Induced by a Thin Film of Fused (Na,K)2SO4 by Electrochemical Impedance Spectroscopy

2013 ◽  
Vol 32 (5) ◽  
pp. 493-501
Author(s):  
S.N. Liu ◽  
W. Su ◽  
W.Y. Lu ◽  
Z.F. Wei ◽  
C.L. Zeng
Keyword(s):  
Thin Film ◽  
Electrochemical Impedance Spectroscopy ◽  
Impedance Spectroscopy ◽  
Hot Corrosion ◽  
Electrochemical Impedance ◽  
Diffusion Flux ◽  
Electrode System ◽  
Corrosion Mechanism ◽  
Low Frequencies ◽  
Nyquist Plots

AbstractTo understand the hot corrosion mechanism of materials it is of significance to establish electrochemical measurements under a thin film of fused salts. In this paper, the hot corrosion behavior of Fe-Cr alloys containing 5, 10 and 25wt% Cr, respectively, in the presence of a fused film of 0.9Na2SO4-0.1K2SO4 (mole fraction) at 1173 K in air has been investigated by electrochemical impedance spectroscopy using a two-electrode system. The Nyquist plots for the corrosion of both Fe-5Cr and Fe-10Cr are composed of a very small semicircle at high frequencies and a line at low frequencies indicating that the corrosion is controlled by the diffusion of oxidants in the fused salt film. The alloys were severely corroded, forming a thick porous corrosion layer containing large amounts of non-protective precipitated Fe oxide particles. Conversely, the Nyquist plots for the corrosion of Fe-25Cr are composed of double capacitive loops, with significantly larger impedance values, which are associated with the formation of a protective Cr2O3 scale. Based on the experimental diffusion impedance results and the theoretic solubility and diffusion coefficient of oxygen in molten salts, respectively, a theoretical value of the diffusion flux of molecular O2 has been calculated.

Effect of the Fe/Cu Relationship Corrosion and low Alloying Elements on Corrosion Behavior of Cast Aluminum Parts

2016 ◽  
Vol 1815 ◽  
Author(s):  
C. Rodríguez-Rivera ◽  
J.A. García-Hinojosa ◽  
F.J. Rodríguez-Gómez
Keyword(s):  
Electrochemical Impedance Spectroscopy ◽  
Aluminum Alloys ◽  
Impedance Spectroscopy ◽  
Corrosion Rate ◽  
Open Circuit Potential ◽  
Electrochemical Impedance ◽  
Open Circuit ◽  
Localized Corrosion ◽  
Corrosion Mechanism ◽  
Corrosion Morphology

ABSTRACTThe aim of this study is to compare the corrosion rate of aluminum alloys for ornamental pieces. Three Fe/Cu relationships were tested in order to improve hardness and brightness in aluminum pieces since these alloys are used in the making of ornamental pieces. The variation on Fe/Cu content could result in modification on corrosion rate, since a metallographic characterization must be carried out identifying the presence of intermetallic phases. The presence of these elements could result in increasing corrosion rate, or even in modification of corrosion morphology, so localized corrosion could be expected.The assessment of corrosion rate was carried out in saline media, since chlorides are ions that promote localized corrosion. Electrochemical techniques (polarization curves and Tafel plots) were used in order to evaluate the attack in aluminum pieces; electrochemical impedance spectroscopy was also employed with voltage amplitude of 10 mV rms, and a frequency range from 10,000 Hz to 0.01 Hz. A typical three electrodes cell was used, exposing an area of one cm2. Before polarization, open circuit potential was monitored for an hour looking for a steady state. All conditions were tested for triplicate.The behavior of open circuit potential vs. time, and polarization curves was analyzed; a corrosion mechanism is proposed according to the electrochemical control. Polarization rate was calculated by using Tafel plots and, an electrochemical impedance spectroscopy analysis by using equivalent electric circuits is shown. Electrochemical impedance will yield information about corrosion morphology that is backed with microscopic inspection.The objective of this study is to compare the corrosion rate of aluminum alloys for ornamental pieces in order to determine the effect of the relationship Fe/Cu on the corrosion mechanism in aluminum parts for ornamental pieces.

scholarly journals Sodium nitrite as a corrosion inhibitor of copper in simulated cooling water

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Marziya Rizvi ◽  
Husnu Gerengi ◽  
Savas Kaya ◽  
Ilyas Uygur ◽  
Mesut Yıldız ◽  
...  
Keyword(s):  
Electrochemical Impedance Spectroscopy ◽  
Impedance Spectroscopy ◽  
Sodium Nitrite ◽  
Electrochemical Impedance ◽  
Pure Copper ◽  
Cooling Water ◽  
Copper Surface ◽  
Corrosion Mechanism ◽  
Maximum Inhibition ◽  
Surface Morphologies

AbstractThe corrosion inhibition behavior of sodium nitrite (NaNO2) towards pure copper (99.95%) in simulated cooling water (SCW) was investigated by means of electrochemical impedance spectroscopy (EIS) and dynamic electrochemical impedance spectroscopy (DEIS). NaNO2 interferes with metal dissolution and reduce the corrosion rate through the formation or maintenance of inhibitive film on the metal surface. Surface morphologies illustrated that the surface homogeneity increased on adding sodium nitrite. Sodium nitrite’s adsorption on copper surface followed the modified form of Langmuir, Freundlich and Frumkin isotherms. Physiosorption mode was involved in the corrosion protection. Electrochemical results revealed an corrosion resistance of copper increases on increasing the inhibitor concentration. The DEIS results indicated that copper corrosion mechanism could be hindered by 50% even after interval of 24 h by optimum concentration of sodium nitrite. The maximum inhibition was achieved with 2000 ppm of NaNO2. With this concentration, inhibition efficiency of up to 61.8% was achievable.

scholarly journals Corrosion Performance of Cu-Based Coins in Artificial Sweat

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
J. Porcayo-Calderon ◽  
R. A. Rodríguez-Díaz ◽  
E. Porcayo-Palafox ◽  
L. Martinez-Gomez
Keyword(s):  
Corrosion Resistance ◽  
Electrochemical Impedance Spectroscopy ◽  
Impedance Spectroscopy ◽  
Electrochemical Impedance ◽  
Polarization Curves ◽  
Corrosion Mechanism ◽  
Corrosion Performance ◽  
Linear Polarization Resistance ◽  
Artificial Sweat ◽  
Anodic Zone

The performance of different Cu-based coins in artificial sweat was evaluated. The electrochemical behavior of the coins was determined by potentiodynamic polarization curves, linear polarization resistance, and electrochemical impedance spectroscopy. Regardless of the chemical composition of the Cu-based coins, they showed similar polarization curves; particularly, the observed similarity in the anodic zone suggests that the corrosion mechanism is the same in all cases. The presence of Ni and Zn does not appreciably affect the corrosion resistance of Cu. However, the presence of both elements affects the corrosion resistance of Cu. Electrochemical impedance spectroscopy measurements showed the presence of three time constants with very similar characteristics, again indicating that the main corrosion mechanism is the same in all cases. Equivalent circuits confirmed that the corrosion performance of the Ni-Zn-Cu coins depends on the Zn/Ni ratio, such that decreasing this value decreases the corrosion resistance of the alloy. In general, nickel has a detrimental effect due to the formation of highly soluble Ni-based corrosion products.

scholarly journals Electrochemical Impedance Spectroscopy (EIS): A Review Study of Basic Aspects of the Corrosion Mechanism Applied to Steels

2020 ◽  
Author(s):  
Héctor Herrera Hernández ◽  
Adriana M. Ruiz Reynoso ◽  
Juan C. Trinidad González ◽  
Carlos O. González Morán ◽  
José G. Miranda Hernández ◽  
...  
Keyword(s):  
Electrochemical Impedance Spectroscopy ◽  
Impedance Spectroscopy ◽  
Electrochemical Impedance ◽  
Chemical Interaction ◽  
Living Organism ◽  
Electrical Circuit ◽  
Metal Corrosion ◽  
Corrosion Mechanism ◽  
Review Reports ◽  
And Control

AC impedance measurements have been applied for over twenty years in electrochemistry and physics to investigate the electrical properties of conductive materials and their interfaces using an external electrical impulse (VOLTAGE, V or CURRENT, I) as driving force. Furthermore, its application has recently appeared to be destined in the Biotechnology field as an effective tool for rapid microbiologic diagnosis of living organism in situ. However, there is no doubt that the electrochemical impedance spectroscopy (EIS) is still one of the most useful techniques around the world for metal corrosion control and its monitoring. Corrosion has long been recognized as one of the most expensive stumbling blocks that concern many industries and government agencies, because it is a steel destructive phenomenon that occurs due to the chemical interaction with aqueous environments and takes place at the interface between metal and electrolyte producing an electrical charge transfer or ion diffusion process. Consequently, it is experimentally possible to determine through the EIS technique the mechanism and control that kinectics of corrosion reactions encounter. First, EIS data is collected through a potentiostat/galvanostat apparatus. After, it is fitted to a mathematical model (i.e. an equivalent electrical circuit, EEC) for its interpretation and analysis, fundamentally seeking a meaningful physical interpretation. Finally, this review reports some basic aspects of the corrosion mechanism applied to steels through the experimental EIS response using Nyquist or Bode plots. Examples are given for different applied electrochemical impedance cases in which steel is under study intentionally exposed to a corrosive aqueous solution by applying a sinusoidal potential at various test conditions.

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