A study of the electrochemical behaviour of cobalt in aqueous H2CO3/HCO3–/CO32– solutions at pH 7–9

2004 ◽  
Vol 82 (5) ◽  
pp. 583-594 ◽  
Author(s):  
Stéphan Simard ◽  
Danick Gallant
Keyword(s):  
Open Circuit Potential ◽  
Competitive Adsorption ◽  
Carbonic Acid ◽  
Acid Corrosion ◽  
Electrochemical Behaviour ◽  
Open Circuit ◽  
Corrosion Process ◽  
Rotating Disc ◽  
Solution Interface ◽  
Potential Decay

The electrochemical behaviour of a cobalt rotating electrode in H2CO3/HCO3–/CO32– aqueous solutions was investigated in the pH region from 7 to 9. The effects of H2CO3/HCO3–/CO32– concentration, pH, and the presence of phosphates as inhibitors was explored using a rotating disc electrode at 1000 rpm. Some potentiodynamic experiments indicate that for pH 8.5 and higher, carbonate and bicarbonate species play a key role on the rate of electrooxidation of cobalt. For pH lower than 8.5, the electrochemical behaviour of cobalt changes drastically and very aggressive corrosion is observed. The involvement of carbonic acid must be considered in the corrosion process of cobalt in this pH region. The study of passive film potential decay under open circuit potential and galvanostatic reduction was performed on preanodized cobalt electrodes in solutions of various compositions. These experiments indicated the phenomena occurring at the electrode–solution interface during the corrosion process. A mechanism involving competitive adsorption of different species is suggested on the basis of the experimental evidence.Key words: cobalt, bicarbonate, phosphate, carbonic acid, corrosion.

scholarly journals Effect of Laminar Flow on the Corrosion Activity of AA6061-T6 in Seawater

Metals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 175
Author(s):  
Gloria Acosta ◽  
Lucien Veleva ◽  
Luis Chávez ◽  
Juan L. López
Keyword(s):  
Laminar Flow ◽  
Open Circuit Potential ◽  
Electrochemical Behaviour ◽  
Corrosion Current ◽  
Open Circuit ◽  
Flow Conditions ◽  
Metal Interface ◽  
Intermetallic Particles ◽  
Power Spectral ◽  
Surface Changes

The electrochemical behaviour and surface changes on AA6061-T6 alloy exposed to Caribbean seawater from the Cozumel Channel for 30 days under laminar flow (0.1 m s−1) were studied, contrasting then with stationary (no flow) conditions. Monitoring of open-circuit potential and current fluctuations, both considered as electrochemical noise (EN), were employed as two nondestructive methods. The calculated corrosion current, based on Rn, was one order higher in laminar flow. The fluctuations of current were transformed in the frequency domain. Their power spectral density (PSD) plots were obtained in order to gain information concerning the dynamic of the spontaneous release of energy during the corrosion process. The value of the exponent β in PSD graphs suggested that the localised corrosion on AA6061-T6 surface occurs as a persistent stationary process, in which dynamic is controlled by oxygen diffusion and its renewal at the metal interface. The changes in the morphology and elemental composition of the formed layers revealed that the localized attacks occurred in the vicinity of intermetallic particles rich in Fe and Cu, which act as cathodes.

Corrosion Behavior of 10CrNiCu Steel Influenced by Thiobacillus Ferrooxidans

2011 ◽  
Vol 233-235 ◽  
pp. 2633-2639
Author(s):  
Kyaw Soe ◽  
Song Mei Li ◽  
Jian Hua Liu ◽  
Mei Yu
Keyword(s):  
Open Circuit Potential ◽  
Thiobacillus Ferrooxidans ◽  
Electrochemical Impedance ◽  
Open Circuit ◽  
Analysis Method ◽  
Microbial Corrosion ◽  
Solution Interface ◽  
Sterile Medium ◽  
Corrosion Behaviors ◽  
Surface Analysis Method

The microbial corrosion behaviors of 10CrNiCu steel influenced by Thiobcillus ferrooxidans (T.f) were studied by microbiological, electrochemical and surface analysis method. The open circuit potential (Eocp) and electrochemical impedance spectroscopy (EIS) of the 10CrNiCu electrodes were measured in immersion electrode way with and without T.f solution at the time of the 0, 2nd, 7th, 14thand 21stdays, respectively. Eocpof the electrode immersed in sterile medium shifted to negative potential with the immersion time while that for immersion in T.f solutions shifted negatively, then positively and finally negatively. EIS results were interpreted with different equivalent circuits of the electrode/biofilm/solution interface. The result of SEM indicated that, after 21 immersion days, there were different sizes of pits on the 10CrNiCu surface occurred in T.f solution while no evidence of the pitting corrosion was observed on the steel surface immersed in the sterile medium.

scholarly journals Corrosion behavior of AH-36 steel in seawater

2020 ◽  
Vol 63 (9) ◽  
pp. 113-118
Author(s):  
Van Chi Nguyen ◽  
◽  
Nhat Linh Cao ◽  
Van Kien Dong ◽  
Hong Quan Le ◽  
...  
Keyword(s):  
Corrosion Behavior ◽  
Open Circuit Potential ◽  
Surface Passivation ◽  
Sample Surface ◽  
Open Circuit ◽  
Corrosion Process ◽  
Anodic Process ◽  
Natural Seawater ◽  
Nacl Solution ◽  
Over Time

In the present work, the corrosion behavior of AH-36 steel in 3% NaCl aqueous solution and natural seawater was studied using a three-electrode cell, Autolab PGSTAT 204N, and Nova 2.0 software by electrochemical methods. It has been established that after contact of the steel with chloride-containing media, the open circuit potential of steel shifts sharply to the negative region, which indicates a decrease in the corrosion resistance of steel in chloride-containing media. In seawater, the stabilization of the open circuit potential is observed within 60 min, and in NaCl solution – 120 min. The constant value of the open circuit potential of steel in seawater is in a more negative range compared to the constant value of the open circuit potential of steel in NaCl solution. In order to study the kinetics of the corrosion process of steel, polarization curves were obtained in the potentiostatic mode. It is shown that the corrosion potentials and currents of the samples decrease over time and tend to constant values. In all cases, the corrosion process in seawater occurs and stabilizes (within 20 min) faster than in NaCl solution. The anode Tafel coefficient takes a value in the range of 0.1-0.2 V, which may indicate the same mechanism of the anodic process. As a result of full-scale tests (Nha Trang, Vietnam), it can be seen that the steel samples are strongly susceptible to corrosion at the initial stage and over time the corrosion rate decreases and tends to a constant value (0.27 g/m2.h). This is due to the sample surface passivation during corrosion tests.

Study of a Decomposing Hydride Phase at Nickel Cathodes by Measurement of Open‐Circuit Potential Decay

1983 ◽  
Vol 130 (9) ◽  
pp. 1825-1836 ◽  
Author(s):  
B. E. Conway ◽  
H. Angerstein‐Kozlowska ◽  
M. A. Sattar ◽  
B. V. Tilak
Keyword(s):  
Open Circuit Potential ◽  
Open Circuit ◽  
Hydride Phase ◽  
Potential Decay
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