scholarly journals Recommended measurement conditions of open-circuit potential of aluminum alloys in sake of estimation of pitting potential

2017 ◽  
Vol 67 (1) ◽  
pp. 16-19
Author(s):  
Keyword(s):  
Aluminum Alloys ◽  
Open Circuit Potential ◽  
Open Circuit ◽  
Pitting Potential

Experimental Study of Propagation Stage of Pitting Corrosion of 20Cr13 Steel

2008 ◽  
Vol 38 ◽  
pp. 238-247
Author(s):  
A.D. Davydov ◽  
V.S. Shaldaev
Keyword(s):  
Pitting Corrosion ◽  
Open Circuit Potential ◽  
Corrosion Potential ◽  
Ph Value ◽  
Open Circuit ◽  
Effect Of Temperature ◽  
Pitting Potential ◽  
Free Corrosion Potential ◽  
External Power Source ◽  
Corrosion Of Steel

The initiation and development of pitting corrosion of steel 20Cr13 in the NaCl solutions with various concentrations, temperatures, and pH values are studied under the potentiostatic conditions and at the free-corrosion potential. The pitting and repassivation potentials are determined using the method of cycling voltammetry. In spite of the fact that thus determined pitting potential is more positive than the corrosion potential (the open-circuit potential Eo.c.), the long-term experiments, which were performed at the free-corrosion potential, showed that pitting corrosion takes place without imposing a potential using an external power source. It is concluded that the probability of pitting corrosion of steel should be determined by comparing the corrosion potential (the open-circuit potential) with the repassivation potential Erp. Steel 20Cr13 is prone to the pitting corrosion, because Erp is more negative than Eo.c.. In the potentiostatic experiments, the variation of the depth and diameter of pits and their number with the time and the effect of temperature and electrode rotation on the pit propagation are studied. The results, which were obtained at the free-corrosion potential, are much less reproducible. In this case, in contrast to the potentiostatic conditions, the pit depth increased only slightly and the pit width increased to a larger extent. The effect of concentration, pH value, and temperature of NaCl solutions on the pit propagation is considered. It is concluded that the data on the development of pitting corrosion under the potentiostatic conditions can be hardly extended to the conditions of free corrosion potential.

scholarly journals The Effect of the Action of Impurities Present in Methanol as a Basis for Automobile Fuel and Their Impact on the Environment

2020 ◽  
Vol 70 (12) ◽  
pp. 4260-4265
Keyword(s):  
Air Pollution ◽  
Aluminum Alloy ◽  
Acid Chloride ◽  
Considerable Increase ◽  
Open Circuit Potential ◽  
Corrosion Potential ◽  
Open Circuit ◽  
Sulfur Oxides ◽  
Pitting Potential ◽  
Hydroxyl Ion

Corrosion of the tank made of aluminum alloy AlMg2,7Mn (5454) has been studied by electrochemical methods in methanolic solution containing different concentrations of acid, chloride, sulphate and water as impurities. In all these cases, the alloy exhibited a sponge passivity. Adding a 1mM solution in fuel leads to a considerable increase in corrosion potential, a 1 mM chlorine solution decreases the pitting potential, and a 1 mM solution of sulfate concentrations does not show any change. In the first phase, due to the hydroxyl ion that surrounds the aluminum, the present water leads to a decrease in the pitting potential.At the same time, the combustion of fuel remains the biggest source of air pollution. The air is polluted by impurities (acids, chlorides, sulphates and water) present in fuels, smoke (incomplete combustion) or nitrogen and sulfur oxides, so it is required to keep them within the limits set by the rules in force. Keywords: aluminium alloy, pitting potential, impurities, polarization curves, open circuit potential

Aluminium corrosion studies. IV. Pitting corrosion

1978 ◽  
Vol 31 (5) ◽  
pp. 943 ◽  
Author(s):  
RT Lowson
Keyword(s):  
Open Circuit Potential ◽  
Chloride Concentration ◽  
Open Circuit ◽  
Aluminium Chloride ◽  
Bulk Solution ◽  
Pitting Potential ◽  
Functional Relationships ◽  
Corrosion Studies ◽  
Thermodynamic Equilibrium Condition ◽  
Chloride Activity

Measurements are reported for the variation of the open-circuit potential, Er, of aluminium in oxygen-saturated sodium salt solutions. The value of Er was independent of SO42- and NO3- concentrations and similar to the value obtained for water (0.04 (s.h.e.)). Er was a function of chloride concentration given by ������������������� Er = -0.475-0.060log[Cl-] V (s.h.e.) at 25�C. There was a less well defined relationship between Er and NO2-, I- and Br-, and a complex relationship with F-. ��� The potentiodynamic characteristics are reported for aluminium in 1-0.01 mol l-1 Cl- oxygen-saturated solutions. Functional relationships were found for E0, Ep, Es and E0' with chloride activity at 5, 25, 50 and 75°C. Hysteresis effects are reported. ��� The experimental results are interpreted in terms of a thermodynamic equilibrium condition between the surface oxide and soluble aluminium chloride. As the system oscillates across the equilibrium conditions the surface will passivate or pit. A critical bulk solution chloride concentration is necessary to maintain the growth of the pit; the experimental value was 1.6 mol l-1 Cl- and the corresponding open-circuit potential was Ecrit = -0.48 V (s.h.e.). The pitting potential, Ev, was interpreted as an overpotential, ηp, given by η = Ep,- Ep-Ecrit.

Influence of pH on the Electrochemical Bahavior of 00Cr15Ni7Mo2Cu2 Supermartensitic Stainless Steel in 3.5% NaCl Solutions

2012 ◽  
Vol 581-582 ◽  
pp. 1058-1061
Author(s):  
Jia Qun Rui ◽  
Jun Li ◽  
Hu Dai Sun ◽  
Kun Yu Zhao ◽  
Zhi Dong Li ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Open Circuit Potential ◽  
Electrochemical Impedance ◽  
Open Circuit ◽  
Pitting Potential ◽  
Supermartensitic Stainless Steel ◽  
Pitting Corrosion Resistance ◽  
Polarization Technique ◽  
Current Densities ◽  
Influence Of Ph

This objective is to study the influence of pH on the electrochemical behavior of 00Cr15Ni7Mo2Cu2 supermartensitic stainless steel in 3.5% NaCl solutions using potentiondynamic polarization technique, open circuit potential tests and electrochemical impedance spectroscopy (EIS).The study reveals that the pitting potential (Eb) is higher, the passivation current densities (ip) is lower and the electrochemical impedance increases with the pH. The results indicate that this stainless steel offer good pitting corrosion resistance with the pH increasing in 3.5% NaCl solutions.

Corrosion Behavior of Sealed Films on Anodized Al Alloy

2011 ◽  
Vol 233-235 ◽  
pp. 1498-1501
Author(s):  
Qi Zhou ◽  
Chun Lin He ◽  
Qing Kui Cai
Keyword(s):  
Potentiodynamic Polarization ◽  
Open Circuit Potential ◽  
Corrosion Behaviour ◽  
Sol Gel ◽  
Open Circuit ◽  
Green Technology ◽  
Al Alloy ◽  
Corrosion Mechanism ◽  
Pitting Potential ◽  
Corrosive Solution

Alumina sol sealing is one of new green technology for anodized Al alloy. The corrosion mechanism of films sealed by sol and corrosion behaviour of films sealed by sol, Na2Cr2O7, boiling water were analyzed by their curves of open circuit voltage-time (E-T) and potentiodynamic polarization curve. It is found that corrosion tendency of sol sealing film is less than other sealed films by E-T inspection. Fluctuation of open-circuit potential is furious in the immersing prophase and slows down in the anaphase for anodized sealed films. At this time corrosive reactions gradually reach steady state. Open-circuit potential greatly waves for the rough sealed films. Potentiodynamic polarization curves of sealed films show that passive area is the longest for films sealed by sol which has the minimum corrosive current , the passivate current, anodic current and cathode current, but the maximum pitting potential and open-circuit potential. Corrosion parameters are the second for the film sealed by dichromate. Anodic reactions are strongly inhibited by sol sealing films in Cl- corrosive solution. Sol sealing films weaken cathode O2 depolarize reaction. Cl- ions erode anodized Al material on which covered with sol film and produce corrosion. The corrosion of sol-gel film goes through two periods: pitting induced phase and pitting corrosion period.

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.

Effects of Environmental Parameters on Marine Corrosion of Aluminium Alloys

2012 ◽  
Vol 569 ◽  
pp. 95-98 ◽  
Author(s):  
Zhen Hua Dan ◽  
Izumi Muto ◽  
Nobuyoshi Hara
Keyword(s):  
Aluminium Alloys ◽  
Open Circuit Potential ◽  
Formation Rate ◽  
Open Circuit ◽  
Lower Solution ◽  
Passive State ◽  
Solution Temperature ◽  
Marine Corrosion ◽  
Pitting Potential ◽  
Sulfate Ions

The marine corrosion of aluminium alloys, AA1100 and AA6061 was investigated in term of the transient of the open circuit potential and polarization behaviors in a simulated marine condition. The pitting potential increased with dilution ratios of artificial seawater. The aluminium alloys passivated at lower potentials in the relatively concentrated solutions. The open circuit potential reached the passive state faster at lower solution temperature than that in higher solution temperature. The pitting potential of AA1100 and AA6061 seems independent of the test solution temperature, and the difference between pitting potential and the corrosion potential became smaller at the lower solution temperature. The involvement of the sulfate compound resulted in the increase in pitting potential and had no effects on the passive current density. The absence of the sulfate ions slowed down the formation rate of the passive film. Especially, the open circuit potential of AA6061 passivated at lower potential due to the absence of the sulfate ions.

Thermal Stability of Anodic Layers on Aluminum Alloys

2015 ◽  
Vol 230 ◽  
pp. 14-18 ◽  
Author(s):  
V. Sokol ◽  
V. Shulgov
Keyword(s):  
Electron Microscopy ◽  
Thermal Stability ◽  
Aluminum Alloy ◽  
Aluminum Alloys ◽  
Open Circuit Potential ◽  
Alloy Composition ◽  
Open Circuit ◽  
Crack Growth Resistance ◽  
Anodic Alumina ◽  
Thermal Stability Of

The thermal stability of anodic alumina layers made by the open circuit potential measurements and electron microscopy is discussed. The crack growth resistance of the anodic alumina layers has been studied depending on the initial aluminum alloy composition and the anodization regimes.

scholarly journals Effect of Aging on Corrosion Behavior of Martensite Phase in Cu-Al-Be Shape Memory Alloy

2018 ◽  
Vol 21 (1) ◽  
pp. 127
Author(s):  
Jafer T. Al-Haidary ◽  
Ali M. Aldulaimi ◽  
Ahmed A. Hamza
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Corrosion Behavior ◽  
Open Circuit Potential ◽  
Salt Water ◽  
Optical Microscope ◽  
Open Circuit ◽  
Martensite Phase ◽  
Cyclic Polarization ◽  
Pitting Potential

The corrosion behavior of martensite phase in Cu-Al-Be shape memory alloy with aging at 150  at time 2,4and 6 hour and quenching ice water with salt, water at room temperature and oil media study by open circuit potential, tafal polarization and cyclic polarization. The microstructure of martensite study by optical microscope and x-ray diffraction(XRD) and transformation temperature was determined by Differential Scanning Calorimeter (DSC).the result show aging martensite at 150   at 2 and 4 hour have high open circuit potential, low corrosion current density , high corrosion potential and pitting potential than  martensite without aging.

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