scholarly journals Studies on Pitting Corrosion of Al–Cu–Li Alloys Part III: Passivation Kinetics of AA2098–T851 Based on the Point Defect Model

Materials ◽  
2019 ◽  
Vol 12 (12) ◽  
pp. 1912 ◽  
Author(s):  
Elmira Ghanbari ◽  
Alireza Saatchi ◽  
Xiaowei Lei ◽  
Digby D. Macdonald
Keyword(s):  
Barrier Layer ◽  
Potential Model ◽  
Electrochemical Impedance ◽  
Passive Layer ◽  
Charge Carriers ◽  
Theoretical Interpretation ◽  
Defect Model ◽  
Kinetics Of Formation ◽  
Kinetics Of

In this paper, the passivation kinetics of AA2098–T851 was investigated by a fundamental theoretical interpretation of experimental results based on the mixed potential model (MPM). The steady state passive layer formed on the AA2098–T851 in NaHCO3 solution in a CO2 atmosphere upon potentiostatic stepping in the anodic direction followed by stepping in the opposite direction was explored. Potentials were selected in a way that both anodic passive dissolution of the metal and hydrogen evolution reaction (HER) occur, thereby requiring the MPM for interpretation. Optimization of the MPM on the experimental electrochemical impedance spectroscopy (EIS) data measured after each potentiostatic step revealed the important role of the migration of Al interstitials in determining the kinetics of passive layer formation and dissolution. More importantly, it is shown that the inequalities of the kinetics of formation and dissolution of the passive layer as observed in opposite potential stepping directions lead to the irreversibility of the passivation process. Finally, by considering the Butler–Volmer (B–V) equation for the cathodic reaction (HER) in the MPM, and assuming the quantum mechanical tunneling of the charge carriers across the barrier layer of the passive film, it was shown that the HER was primarily controlled by the slow electrochemical discharge of protons at the barrier layer/solution (outer layer) interface.

Role of ionic strength in the kinetics of formation of the monochelate of nickel(II) with heptane-3,5-dione

1992 ◽  
Vol 24 (4) ◽  
pp. 359-368 ◽  
Author(s):  
María Luisa Moyá ◽  
Amalia Rodriguez ◽  
Francisco Sánchez ◽  
Carlos Blanco ◽  
Michael J. Hynes
Keyword(s):  
Ionic Strength ◽  
Kinetics Of Formation ◽  
Kinetics Of

Role of chromium in anomalous behaviour of the passive layer in Ni-Cr-Mo alloys in 1M HCl solution

CORROSION ◽  
10.5006/3767 ◽  
2022 ◽  
Author(s):  
Malvika Karri ◽  
Amit Verma ◽  
J.B. Singh ◽  
Sunil Kumar Bonagani ◽  
U.K. Goutam
Keyword(s):  
Corrosion Resistance ◽  
Electrochemical Impedance ◽  
Corrosion Behaviour ◽  
Underlying Mechanism ◽  
Passive Layer ◽  
X Ray ◽  
Superior Corrosion Resistance ◽  
Hcl Solution ◽  
Cr2o3 Layer

This work seeks to understand the underlying mechanism involved in passivity of Ni-Cr-Mo alloys in a less concentrated HCl solution (1M) by systematically varying contents of Cr and Mo solutes in model Ni-Cr-Mo alloys. Corrosion behaviour was evaluated based on potentiodynamic polarisation tests carried out in conjunction with electrochemical impedance and x-ray photoelectron spectroscopies of passive films that formed on alloys during their exposure to the HCl solution. Results have shown that an increase in Mo alone is not sufficient to improve the corrosion resistance of the alloys at lower concentrations of HCl. Optimum concentrations of Cr and Mo solutes have been found to be in the vicinity of ~17 wt.% Cr and ~19 wt.% Mo for superior corrosion resistance of the alloys. This was attributed to the protection of the Cr2O3 layer as a consequence of the enrichment of Mo6+ ions in the passive film in 1M HCl solution.

The role of surface films in the kinetics of oxygen evolution at Pd + Au alloy electrodes

1962 ◽  
Vol 269 (1338) ◽  
pp. 419-440 ◽  
Keyword(s):  
Transition Region ◽  
Oxygen Evolution ◽  
Barrier Layer ◽  
Alkaline Solutions ◽  
Surface Films ◽  
Discharge Process ◽  
Polarization Current ◽  
Transient Effects ◽  
Kinetics Of

The kinetics of anodic oxygen evolution have been studied on Pd, Au and Pd + Au alloys in ultra-pure sulphuric acid and potassium hydroxide solutions and mechanisms of the processes involved are proposed. The role of barrier-layer films in determining the kinetic behaviour is demonstrated and supported by self-consistent interpretations of the Tafel slopes and the e.m.f. decay behaviour observed on open-circuit. Transient effects, characteristic of barrier-layer films, are observed when changes of the polarization current are made. At Au, and the gold-rich alloys in alkaline solution, a transition region in the currentpotential relation is observed which probably corresponds to a limiting high coverage of the electrochemically active surface with adsorbed reaction intermediates. The transition region corresponds to an onset of passive behaviour. In acid solutions, only the lower Tafel region is observed which has the same Tafel constants b and i 0 as those for the lower Tafel line in alkaline solutions indicating that the discharge process involves water rather than OH - ions, irrespective of pH. The relation of exchange currents to composition of the alloys is considered.

An Evaluation of the Plane Strain Compression Test. III. Experimental Study of the Friction Test: The Role of the Metallurgical Parameters of Die and Sheet

1982 ◽  
Vol 104 (4) ◽  
pp. 538-544 ◽  
Author(s):  
F. Delamare ◽  
J. Kubie´
Keyword(s):  
Experimental Study ◽  
Shear Stress ◽  
Chemical Nature ◽  
Marked Effect ◽  
Friction Test ◽  
Good Reliability ◽  
Plane Strain Compression Test ◽  
Kinetics Of Formation ◽  
Kinetics Of

This paper deals with the influence of the metallurgical parameters of dies and sheet on the friction shear-stress which could be measured by P.S.C.T. The metallurgical parameters of the dies have a marked effect on the kinetics of formation of transfer layers. The metallurgical parameters of the sheet have an effect both on the kinetics of formation, and the chemical nature of the transfer layers. Many parameters must be controlled to have good reliability in PSCT. Then the results can be correlated with boundary lubrication in cold rolling.

The Effect of Magnetic Fields on Corrosion in Pipeline Steel

2007 ◽  
Author(s):  
Joshua E. Jackson ◽  
Angelique N. Lasseigne-Jackson ◽  
David L. Olson ◽  
Brajendra Mishra ◽  
Meredith S. Heilig ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Hydrogen Content ◽  
Electrochemical Impedance ◽  
Pipeline Steel ◽  
Cold Work ◽  
Passive Layer ◽  
Laboratory Research ◽  
Electromagnetic Current

Measurements performed in earlier research have indicated a strong effect of magnetization on hydrogen content (thermodynamics) as well as cracking, and pitting (kinetics) in pipeline steels as described in Sanchez (2005) and Sanchez et al. (2005). The effect of cold work, further increasing hydrogen content, cracking, and pitting, was also assessed. Theoretical descriptions of both thermodynamic and kinetic interpretations of the observed effect is described and correlated to observed results. There are two ways that electromagnetic current influences corrosion: (1) D/C currents (under applied or Remanent magnetic fields) and A/C electric currents (which create electromagnetic fields through Lenz’s Law) may influence magnetocorrosion as described in this paper, and (2) A/C currents also have the potential to strip the protective passive layer from materials and greatly accelerate corrosion. Electrochemical charging is currently being performed at varied magnetic field strengths to assess the nature of the observed influence of magnetization on both hydrogen content (thermodynamic) and cracking/pitting (kinetic), including the role of controlled-roll cold working. Naval and maritime use of A/C and D/C electric-powered systems including propulsion drives, servos, and controls, is increasing rapidly in sea-going operation and potential for stray currents is an increasing risk. Magnetic flux leakage inspection, using saturating magnetic fields, is widely used for reliable and accurate inspection of pipeline corrosion and wall thickness. Previous laboratory research shows a significant increase in both pipeline steel hydrogen content in steel and pitting and cracking after electrochemical hydrogen charging under an applied two Tesla magnetic field. Cold work was observed to further increase the observed effects. The thermodynamic auxiliary functions, using a derivation of Helmholtz free energy, are examined to assess the thermodynamic effects of magnetization on hydrogen content. The effect of magnetization on the thermodynamics of electron spin configurations, interstitial solute-induced strain, magnetostriction (directional strain induced in steel from an applied magnetic field) are considered. Kinetic interpretations of possible interactions with the Helmholtz Double (capacitor-like) Layer and the Gouy-Chapman (diffuse) layer that may lead to increased diffusion and thus to hydrogen supersaturation are described. Electrochemical impedance measurements are being performed to assess the influence of applied magnetic fields on the Helmholtz and Gouy-Chapman layers.

Kinetics of Formation and Dissolution of Weak Polyelectrolyte Multilayers:  Role of Salt and Free Polyions

Langmuir ◽  
2002 ◽  
Vol 18 (14) ◽  
pp. 5607-5612 ◽  
Author(s):  
D. Kovacevic ◽  
S. van der Burgh ◽  
A. de Keizer ◽  
M. A. Cohen Stuart
Keyword(s):  
Polyelectrolyte Multilayers ◽  
Kinetics Of Formation ◽  
Kinetics Of
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