Communication—Revisiting Thin Foil Penetration Technique for Intergranular Corrosion Tests on Aluminum Alloys

Oltra, R.; Bonzom, Rémy

doi:10.1149/2.0951606jes

Cited by 7 publications

(9 citation statements)

References 4 publications

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“…The corrosion behavior of such a thin foil was studied in a previous work related to the application of the thin foil penetration technique on this kind of thin target . During immersion tests (in 0.1 M NaCl solution) under potentiostatic conditions, it was demonstrated that the alloy is sensitive to IGC.…”

Section: Methodsmentioning

confidence: 99%

A novel methodology to study localized corrosion under atmospheric simulated corrosion conditions: Toward a continuous monitoring of the corrosion damage on AA2024

Oltra¹,

Colard²,

Bonzom³

2016

Materials & Corrosion

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There is a need to develop instrumented witness plates which would be possible to expose in natural environments after laboratory validation. In conventional laboratory scale test chambers, the main difficulty remains the access of any kind of sensor to the tested metallic target for continuous monitoring. It is proposed to generate a well‐controlled spray by an ultrasonic nozzle focused on the surface of very thin AA2024 foils positioned in a compact test cell which renders possible the access to the backside of the target. Validation in terms of corrosion damage of remote sequential experimental procedure using an ultrasonic nozzle programmed to pulse is illustrated.

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Section: Methodsmentioning

confidence: 99%

A novel methodology to study localized corrosion under atmospheric simulated corrosion conditions: Toward a continuous monitoring of the corrosion damage on AA2024

Oltra¹,

Colard²,

Bonzom³

2016

Materials & Corrosion

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“…13 The complementary methodology improvements, i.e. the control of the IGC initiation and the chemical analysis of the electrolyte trapped inside the grain boundary network, will be described and applied to assess quantitatively the IGC propagation on Al-Cu alloys.…”

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“…13 Compared to this preliminary work 13 carried on TL * L exposed surfaces for which penetrating IG paths presented an important tortuosity, in this work, the IGC propagation was studied in the L direction to approach the intrinsic propagation rate, as explained before. The optical detection consisted in detecting the purged electrolyte trapped in the "IG crevice" cavities emerging along full penetrating defects and forming droplets (Figure 2a).…”

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confidence: 99%

“…The modified foil penetration experiments 13 provided an "easy" access to the rear side of the foil. The initial version of the foil penetration method was, in fact, based on this leaching which soaked the filter paper which was replaced in this work by a pH-indicator paper.…”

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confidence: 99%

“…12 In this paper we present an alternative detection method for the foil penetration technique 1 to strengthen the robustness of the measurement of the penetration rates of IG "fissures". 13 The complementary methodology improvements, i.e. the control of the IGC initiation and the chemical analysis of the electrolyte trapped inside the grain boundary network, will be described and applied to assess quantitatively the IGC propagation on Al-Cu alloys.…”

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Optical and Chemical Monitoring during Foil Penetration Experiments to Study Intergranular Corrosion in AA2024

Bonzom

Oltra

2018

J. Electrochem. Soc.

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A modified version of the foil penetration technique based on an optical detection of the full penetrating intergranular defects through thin foils was applied to AA2024 samples of various thicknesses in contact with a dilute chloride solution. As the rear side of the foil was free during the experiments, it was straightforward to measure the pH of the electrolyte trapped inside the grain boundary network leaking through the emerging defects on the rear side of the foils. The penetration regime in the longitudinal direction was determined for various exposure and electrochemical conditions confirming the decrease of the propagation kinetics as function of the depth of the intergranular defects. pH measurements were used to support mass transport simulation inside a pore electrode mimicking the propagation of the anodic head of grain boundaries. After validation under potentiostatic conditions, the same modelling approach was applied under free corrosion conditions, to discuss the location of cathodic areas during immersion and droplet exposures. Frankel and coworkers 1 considered the anisotropy of the intergranular corrosion process and performed foil penetration tests using various electrochemical conditions. They proposed that the propagation rate of intergranular corrosion followed a power law of the following type:where d is either the nominal thickness of the full penetrated foil or the resulting IG path length, a and n are constants (n is between 0 and 1) and t the time for the full penetration. To discuss these results in terms of IG propagation rate the raw data can be inverted and expressed as the depth of the fastest growing site as a function of time. However the physical meaning of the exponent and its value as function the nature of the alloy have not been discussed to our knowledge. Nevertheless, interesting work described in Ref. 2 illustrated application of such a law (relation 1) deduced from laboratory experiments to operational aircraft. In these practical cases there was a large variation in corrosion growth rates from one section of a wing to the next or from an aircraft to the next. But it was demonstrated that it was possible to provide a distribution for coefficients of relation (1), especially for coefficient a, which could be deduced from documented corrosion data collected, for example, from repair data.Relation (1) which means that the intergranular (IG) propagation rate on aluminum alloys (AA2024) is decreasing as function of the IG path length has been validated under potentiostatic conditions. 1 Moreover this trend has been also frequently discussed in other studies under free corrosion conditions. 3,4 Nevertheless, the origin of this feature has not been largely discussed quantitatively, especially as the inner surface of the "IG crevice" behind the active anodic head at the point of attack 5 can also suffer dissolution at a reduced rate and at long exposures as illustrated in different works showing a blunting of the IG path.6,7 Consequently the mass transport and/or the ohmic dr...

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Intergranular corrosion propagation rate of 2024 alloy investigated via the “one-dimensional artificial pit” technique

Bonzom

Oltra

2016

Corrosion Science

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Communication—Revisiting Thin Foil Penetration Technique for Intergranular Corrosion Tests on Aluminum Alloys

Cited by 7 publications

References 4 publications

A novel methodology to study localized corrosion under atmospheric simulated corrosion conditions: Toward a continuous monitoring of the corrosion damage on AA2024

A novel methodology to study localized corrosion under atmospheric simulated corrosion conditions: Toward a continuous monitoring of the corrosion damage on AA2024

Optical and Chemical Monitoring during Foil Penetration Experiments to Study Intergranular Corrosion in AA2024

Intergranular corrosion propagation rate of 2024 alloy investigated via the “one-dimensional artificial pit” technique

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Communication—Revisiting Thin Foil Penetration Technique for Intergranular Corrosion Tests on Aluminum Alloys

Cited by 7 publications

References 4 publications

A novel methodology to study localized corrosion under atmospheric simulated corrosion conditions: Toward a continuous monitoring of the corrosion damage on AA2024

A novel methodology to study localized corrosion under atmospheric simulated corrosion conditions: Toward a continuous monitoring of the corrosion damage on AA2024

Optical and Chemical Monitoring during Foil Penetration Experiments to Study Intergranular Corrosion in AA2024

Intergranular corrosion propagation rate of 2024 alloy investigated via the “one-​dimensional artificial pit” technique

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Intergranular corrosion propagation rate of 2024 alloy investigated via the “one-dimensional artificial pit” technique