Deformation of Passive Films

Bubar, S. F.; Vermilyea, D. A.

doi:10.1149/1.2426770

Cited by 56 publications

(23 citation statements)

References 4 publications

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“…Another factor of possible importance was hydrodynamics, although its influence was not investigated in this study. Since the method of data presentation requires accurate knowledge of the bare metal area produced by the DWA, supplementary film fracture experiments were conducted using the technique of Bubar and Vermilyea (27) to characterize passive film ductility. The fracture strains observed were of the order of 10 -4, indicating negligible film ductility and the validity of Eq.…”

Section: Discussionmentioning

confidence: 99%

A Study of Transient Corrosion in the Iron‐Caustic System by Use of a Drop Weight Apparatus

Diegle

Vermilyea

1975

J. Electrochem. Soc.

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Repassivation current transients in the Fe-caustic system were measured after straining potentiostatically polarized electrodes with a drop weight apparatus, which could produce strains of about 5% in 1 msec. Peak current densities varied from 0.3 to 3.8 A/cm" depending on electrode potential, electrolyte concentration, and temperature, and initial film coverage was complete in less than 1 or 2 msec. The amount of corrosion accompanying passive film formation was not very sensitive to the above-mentioned electrochemical variables, and it ranged from 1 • 10 -3 to 5 X 10 -3 coulombs/cme. Repassivation was facilitated by additions to the test electrolyte of the anodic dissolution product HFeO2-. The total corrosion up to 1 sec following straining was a strong function of potential, electrolyte concentration, and temperature, as was the quasi steady-state current density. The depth of corrosion 1 sec after straining ranged from twenty to several hundred angstrom units. The relevance of these results to several mechanistic models of caustic cracking is discussed.The study of corrosion transients in alloy-corrodent systems exhibiting stress corrosion cracking (SCC) is of great importance in understanding the mechanism (s) of cracking. For instance, it has been proposed that susceptibility to SCC is in part determined by the amount of corrosion occurring after fracture of a protective passive film at the crack tip, and before repassivation occurs (1-4). Comparison of the effects of such pertinent electrochemical variables as electrode potential and electrolyte concentration on the kinetics of transient corrosion and on the rate of crack propagation during SCC should provide insight into this film rupture mechanism. Indeed, in a broader sense results can hopefully help determine the applicability to caustic SCC (CSCC) of the several types of models based on anodic dissolution, such as those involving periodic film rupture and intermittent crack advance (1-4), and others supporting uniform crack advance by corrosion at a continuously active crack tip (5, 6).Although repassivation phenomena have been intensely investigated, relatively few studies have been made in systems which exhibit SCC. Recent exceptions are the studies of Beck (7), and Ambrose and Kruger (8,9). Beck measured the repassivation rate of Ti in HC1 electrolytes after specimen fracture, and he observed peak current densities of several amperes per square centimeter and initiation of repassivation in milliseconds due to monolayer oxide film formation. Ambrose and Kruger, using an abrasion technique called triboellipsometry (8), studied the repassivation of mild steel in NO.~-and NO2-solutions (8), and of Ti in NQ-and C1-electrolytes (9). Again, large current transients resulted and repassivation began within several milliseconds after the cessation of abrasion.This work is part of a continuing study designed to determine the validity of the film rupture theory of SCC as recently formulated (1, 2). The Fe-caustic system was chosen as a model for investigatio...

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Section: Discussionmentioning

confidence: 99%

A Study of Transient Corrosion in the Iron‐Caustic System by Use of a Drop Weight Apparatus

Diegle

Vermilyea

1975

J. Electrochem. Soc.

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“…This is the case for aluminum in sodium sulfate solutions from --0.56 to ~l.8V, in ammonium borate solutions at --0.06V (22), or at potentials lower than the pitting potential in solutions containing NaC1 or NaNOa. An increase in the anodic current density will be observed as a result of the rupture and reformation of the oxide film, but no localized corrosion will be detected.…”

Section: Science and Technologymentioning

confidence: 94%

“…The existence of such flaws has been questioned by Pryor (15,16). As the aluminum oxide film is very fragile (22) in deformation the film breaks easily, and the bare metal is exposed to the solution. Before straining, the aluminum wire carries an air-formed oxide film of the order of 30A (15).…”

Section: Science and Technologymentioning

confidence: 99%

Anodic Behavior of Aluminum Straining and a Mechanism for Pitting

Wexler

Galvele

1974

J. Electrochem. Soc.

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“…Due to generating an additive stress which increased dislocation multiplication and motion, the passive film decreased the yield stress of the specimen from the flow stress of specimen without film . Other researchers have performed bulk experiments which enable measurements of passive film strength, but these usually couple both the bulk metallic alloy as well as the very thin passive film [29][30][31][32].…”

Section: 3 Film Fracture Testing In Corrosive Environmentsmentioning

confidence: 99%

Development of experimental verification techniques for non-linear deformation and fracture on the nanometer scale.

Moody¹,

Bahr²

2005

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This work covers three distinct aspects of deformation and fracture during indentations. In particular, we develop an approach to verification of nanoindentation induced film fracture in hard film / soft substrate systems ; we examine the ability to perform these experiments in harsh environments; we investigate the methods by which the resulting deformation from indentation can be quantified and correlated to computational simulations, and we examine the onset of plasticity during indentation testing.First, nanoindentation was utilized to induce fracture of brittle thin oxide films on compliant substrates . During the indentation, a load is applied and the penetration depth is continuously measured . A sudden discontinuity, indicative of film fracture, was observed upon the loading portion of the load-depth curve . The mechanical properties of thermally grown oxide films on various substrates were calculated using two different numerical methods . The first method utilized a plate bending approach by modeling the thin film as an axisymmetric circular plate on a compliant foundation . The second method measured the applied energy for fracture. The crack extension force and applied stress intensity at fracture was then determined from the energy measurements.Secondly, slip steps form on the free surface around indentations in most crystalline materials when dislocations reach the free surface . Analysis of these slip steps provides information about the deformation taking place in the material . Techniques have now been developed to allow for accurate and consistent measurement of slip steps and the effects of crystal orientation and tip geometry are characterized . These techniques will be described and compared to results from dislocation dynamics simulations.iii Finally, the stress required to cause fracture of passive films on stainless steels was studied using nanoindentation under in situ and ex situ conditions . For films formed at a passive potential, the alloy chemistry dominated the film strength . Increasing the electrolyte salt concentration from O .O1M NaCl to O .1M NaCl and changing the substrate on which the film was grown from 904L to 304 stainless steels reduced the applied tensile stress for fracture from 1 .74GPa to 1 .63GPa and from 1 .76GPa to 1 .63GPa, respectively . Trends in film strength as a function of environment are the same between in situ and ex situ testing, suggesting the two tests are both feasible methods of analyzing environmental effects on film strength.iv CONTENTS

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Deformation of Passive Films

Cited by 56 publications

References 4 publications

A Study of Transient Corrosion in the Iron‐Caustic System by Use of a Drop Weight Apparatus

A Study of Transient Corrosion in the Iron‐Caustic System by Use of a Drop Weight Apparatus

Anodic Behavior of Aluminum Straining and a Mechanism for Pitting

Development of experimental verification techniques for non-linear deformation and fracture on the nanometer scale.

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