On the Kinetics of the Breakdown of Passivity of Preanodized Aluminum by Chloride Ions

Foroulis, Z. A.; Thubrikar, Mano J.

doi:10.1149/1.2134003

Cited by 119 publications

(32 citation statements)

References 9 publications

(17 reference statements)

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“…[1], could generate a local solution pH of~3.8, which is in good agreement with the experimental findings. [64,65] It is reasonable to conclude that, following the adsorption of chloride ions onto the oxide surfaces covering a fatigue pre-crack, hydration and chemical reactivity (when a sufficient supply of chloride ions is available) will lead to generation of a gel-like surface film and a local aqueous environment containing oxy-chloride species, such as Al(OH) 2 Cl and Al(OH)Cl 2 , [71][72][73][74][75] with a pH less than 4 controlled by the equilibrium process:…”

Section: Local Solution Chemistry Within Pre-cracks and Propagatinmentioning

confidence: 99%

Stress Corrosion Cracking in Al-Zn-Mg-Cu Aluminum Alloys in Saline Environments

Holroyd

Scamans

2012

Metall Mater Trans A

108

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Stress corrosion cracking of Al-Zn-Mg-Cu (AA7xxx) aluminum alloys exposed to saline environments at temperatures ranging from 293 K to 353 K (20°C to 80°C) has been reviewed with particular attention to the influences of alloy composition and temper, and bulk and local environmental conditions. Stress corrosion crack (SCC) growth rates at room temperature for peak-and over-aged tempers in saline environments are minimized for Al-Zn-Mg-Cu alloys containing less than~8 wt pct Zn when Zn/Mg ratios are ranging from 2 to 3, excess magnesium levels are less than 1 wt pct, and copper content is either less than~0.2 wt pct or ranging from 1.3 to 2 wt pct. A minimum chloride ion concentration of~0.01 M is required for crack growth rates to exceed those in distilled water, which insures that the local solution pH in crack-tip regions can be maintained at less than 4. Crack growth rates in saline solution without other additions gradually increase with bulk chloride ion concentrations up to around 0.6 M NaCl, whereas in solutions with sufficiently low dichromate (or chromate), inhibitor additions are insensitive to the bulk chloride concentration and are typically at least double those observed without the additions. DCB specimens, fatigue pre-cracked in air before immersion in a saline environment, show an initial period with no detectible crack growth, followed by crack growth at the distilled water rate, and then transition to a higher crack growth rate typical of region 2 crack growth in the saline environment. Time spent in each stage depends on the type of precrack (''pop-in'' vs fatigue), applied stress intensity factor, alloy chemistry, bulk environment, and, if applied, the external polarization. Apparent activation energies (E a ) for SCC growth in Al-Zn-Mg-Cu alloys exposed to 0.6 M NaCl over the temperatures ranging from 293 K to 353 K (20°C to 80°C) for under-, peak-, and over-aged low-copper-containing alloys (<0.2 wt pct) are typically ranging from 80 to 85 kJ/mol, whereas for high-copper-containing alloys (>~0.8 wt pct), they are typically ranging from 20 to 40 kJ/mol for under-and peak-aged alloys, and based on limited data, around 85 kJ/mol for over-aged tempers. This means that crack propagation in saline environments is most likely to occur by a hydrogen-related process for low-copper-containing Al-Zn-Mg-Cu alloys in under-, peak-and over-aged tempers, and for high-copper alloys in under-and peak-aged tempers. For over-aged high-copper-containing alloys, cracking is most probably under anodic dissolution control. Future stress corrosion studies should focus on understanding the factors that control crack initiation, and insuring that the next generation of higher performance Al-Zn-Mg-Cu alloys has similar longer crack initiation times and crack propagation rates to those of the incumbent alloys in an over-aged condition where crack rates are less than 1 mm/month at a high stress intensity factor.

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Section: Local Solution Chemistry Within Pre-cracks and Propagatinmentioning

confidence: 99%

Stress Corrosion Cracking in Al-Zn-Mg-Cu Aluminum Alloys in Saline Environments

Holroyd

Scamans

2012

Metall Mater Trans A

108

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“…Not surprisingly, this discontinuity is observed at the same Clconcentration where the Ē pit vs. log [Cl -] plot changes slope ( Figure B12). Similarly, the relationship between τ and [Cl -] has been observed to be a strong function of chloride concentration by both Foroulis (42) and Bogar (44). Literature values of n for pure Al (42) and Al 1199 (44) have been reported in the range of 0.1 to 2.5 respectively.…”

Section: B44 CL Dependence Of ē Pitmentioning

confidence: 78%

“…Similarly, the relationship between τ and [Cl -] has been observed to be a strong function of chloride concentration by both Foroulis (42) and Bogar (44). Literature values of n for pure Al (42) and Al 1199 (44) have been reported in the range of 0.1 to 2.5 respectively. Here we calculate values ranging from about 0 to 2.…”

Section: B44 CL Dependence Of ē Pitmentioning

confidence: 78%

“…Another metric that has been used to describe the [Cl -] dependence of pit initiation behavior is induction time, τ. Plots of log (τ -1 ) vs. log [Cl -] have been used to generate estimates of a reaction order for pit initiation in aluminum (41)(42)(43)(44). If τ is taken to be inversely proportional to the rate of reaction, then the following rate equation can be written:…”

Section: B44 CL Dependence Of ē Pitmentioning

confidence: 99%

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Determination of critical length scales for corrosion processes using microelectroanalytical techniques.

Zavadil

Wall²

2004

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A key factor in our ability to produce and predict the stability of metal-based macro-to nano-scale structures and devices is a fundamental understanding of the localized nature of corrosion. Corrosion processes where physical dimensions become critical in the degradation process include localized corrosion initiation in passivated metals, microgalvanic interactions in metal alloys, and localized corrosion in structurally complex materials like nanocrystalline metal films under atmospheric and inundated conditions. This project focuses on two areas of corrosion science where a fundamental understanding of processes occurring at critical dimensions is not currently available. Sandia will study the critical length scales necessary for passive film breakdown in the inundated aluminum (Al) system and the chemical processes and transport in ultra-thin water films relevant to the atmospheric corrosion of nanocrystalline tungsten (W) films. Techniques are required that provide spatial information without significantly perturbing or masking the underlying relationships. Al passive film breakdown is governed by the relationship between area of the film sampled and its defect structure. We will combine low current measurements with microelectrodes to study the size scale required to observe a single initiation event and record electrochemical breakdown events. The resulting quantitative measure of stability will be correlated with metal grain size, secondary phase size and distribution to understand which metal properties control stability at the macro-and nano-scale. Mechanisms of atmospheric corrosion on W are dependent on the physical dimensions and continuity of adsorbed water layers as well as the chemical reactions that take place in this layer. We will combine electrochemical and scanning probe microscopic techniques to monitor the chemistry and resulting material transport in these thin surface layers. A description of the length scales responsible for driving the corrosion of the nanocrystalline metal films will be developed. The techniques developed and information derived from this work will be used to understand and predict degradation processes in microelectronic and microsystem devices critical to Sandia's mission.

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“…Initially, the naturally-occurring oxide layer on the aluminium protects the underlying metal from corrosive attack; however, chloride ions will attack the oxide along its grain boundaries and, by forming a soluble chloride, will expose fresh oxide to attack. 22 Eventually, most of the oxide will be removed, and then the metal will be open to attack.…”

Section: Discussionmentioning

confidence: 99%

A rapid technique for assessing the moisture ingress susceptibility of plastic‐encapsulated integrated circuits

Chwastek

Shaw

1987

Quality & Reliability Eng

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The equipment and associated methodology of a new technique for checking the susceptibility of plastic‐encapsulated ICs to moisture ingress is presented. The basis of the new technique is to immerse unbiased ICs in a salt solution and to subject them to high temperatures (in the range 120°C to 175°C) and to high pressures (2 to 9 atmospheres). At the highest temperature, results can be obtained within a few hours, although a 20 h test at 165°C is suggested as a screen for components. The test is extremely simple to carry out and a testing facility can be quickly established. Using CMOS components from five different vendors, good agreement has been obtained between the results from the new test and the results from a biased 85°C/85 percent RH test.

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On the Kinetics of the Breakdown of Passivity of Preanodized Aluminum by Chloride Ions

Cited by 119 publications

References 9 publications

Stress Corrosion Cracking in Al-Zn-Mg-Cu Aluminum Alloys in Saline Environments

Stress Corrosion Cracking in Al-Zn-Mg-Cu Aluminum Alloys in Saline Environments

Determination of critical length scales for corrosion processes using microelectroanalytical techniques.

A rapid technique for assessing the moisture ingress susceptibility of plastic‐encapsulated integrated circuits

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