Understanding localized corrosion

Frankel, G. S.; Sridhar, Narasi

doi:10.1016/s1369-7021(08)70206-2

Cited by 210 publications

(121 citation statements)

References 32 publications

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“…T ≥ T crit [6] E max ≥ E crit [7] r ≥ r crit [8] Similarly, the basic criterion for salt film formation and diffusion control of an open pit, i diss,max ≥ i lim , can also be developed into three other specific criteria:…”

Section: C764mentioning

confidence: 99%

Localized Corrosion: Passive Film Breakdown vs. Pit Growth Stability: Part III. A Unifying Set of Principal Parameters and Criteria for Pit Stabilization and Salt Film Formation

Scully

Frankel

2018

J. Electrochem. Soc.

115

132

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The framework for pit stability established in Part II of this series is elaborated upon and expanded. The maximum pit dissolution current density, i diff,max , which depends on temperature and maximum potential at the pit surface in a given pit environment, is proposed and compared with the diffusion current density to determine the conditions for pit stability and salt film formation. For an open pit, the criterion for pit stability is that i diss,max must be greater than or equal to the critical diffusion current density required for maintaining a critical local environment for active dissolution, i diff,crit . The critical condition of i diss,max = i diff,crit is associated with three parameters that must be exceeded for stabilization of an open pit: critical temperature T crit , critical potential E crit and critical pit depth r crit . Analogously, the criterion for salt film formation is i diss,max must further exceed the diffusion-limited current density i lim , and three parameters associated with salt film formation are: saturation temperature T sat , saturation potential E sat and saturation pit depth r sat . Unifying criteria for control of pit growth by charge transfer or diffusion are proposed, which provide interrelationships for all principle parameters. The pit stability criteria for covered pits, such as metastable pits, are also described.

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Section: C764mentioning

confidence: 99%

Localized Corrosion: Passive Film Breakdown vs. Pit Growth Stability: Part III. A Unifying Set of Principal Parameters and Criteria for Pit Stabilization and Salt Film Formation

Scully

Frankel

2018

J. Electrochem. Soc.

115

132

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“…69,70 The corrosion attack is also known to be stabilized by the metal cation hydrolysis and Cl -migration toward anodic sites. 71,72 In the cathodic areas, hydroxide is produced and Na + (aq) ions are accumulated, resulting in high pH values, stabilizing the Mg(OH) 2 passive film. The overall corrosion reaction 2-4 becomes 5; 67,68 Mg (s) + 2H 2 O (aq) → Mg(OH) 2 (s) + H 2 (g) [5] While the atmospheric corrosion of Mg alloys in the presence of NaCl at RH = 95% is expected to proceed in a similar way, there are significant differences in comparison to corrosion during immersion because of the small amount of aqueous solution available and the absence of large scale convection.…”

Section: Discussionmentioning

confidence: 99%

Atmospheric Corrosion of Mg Alloy AZ91D Fabricated by a Semi-Solid Casting Technique: The Influence of Microstructure

Esmaily

Mortazavi

Svensson

et al. 2015

J. Electrochem. Soc.

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The atmospheric corrosion behavior of alloy AZ91D produced by a semi-solid metal (SSM) technique and by conventional high pressure die casting (HPDC) was investigated for up to 1176 hours in the laboratory. Alloy AZ91D in the SSM state was fabricated using a rheocasting (RC) technique in which the slurry was prepared by the RheoMetal process. Exposures were performed in 95% RH air at 22 and 4 • C. The RC alloy AZ91D exhibited significantly better corrosion resistance than the HPDC material at two temperatures studied. The effect of casting technology on corrosion is explained in terms of the microstructural differences between the materials. For example, the larger number density of cathodic β phase particles in the HPDC material initially causes relatively rapid corrosion compared to the RC material. During later stages of corrosion, the more network-like β phase particles in the RC alloy act as a corrosion barrier, further improving the relative corrosion resistance of the RC material. Conventional magnesium-aluminum (Mg-Al) alloys, i.e., AZ91D, AM50A and AM60B, offer an exceptional combination of ambient temperature strength and ductility, and good die-castability.1-4 Cast components made of Mg-Al alloys are usually cast by conventional high pressure die casting (HPDC). Despite its advantages over many other casting techniques for producing cast Mg-Al components, there are some inherent problems associated with HPDC. For example, there is a tendency for hot tearing during HPDC due to a relatively wide freezing range and a low solidus temperature. Also, a relatively high fraction of trapped air porosity may form during the turbulent die filling, especially in thick-walled components. Additionally, insufficient resistance to atmospheric and aqueous corrosion sometimes limits Mg-Al alloys applications in the fields of automobiles, aerospace, electronics, etc.5-8 During the past two decades, there have been extensive efforts to increase the corrosion resistance of Mg-Al alloys. Much of the effort has concentrated on the use of various coating systems such as chemical conversion coatings, anodizing, gas-phase deposition processes electro-or electro-less plating, and organic coating. [9][10][11][12][13][14][15] Lowering the impurity levels, alloying, rare earth additions, and heattreatment have also been explored to increase the corrosion resistance of these alloys. [16][17][18][19][20] Alternative casting processes are being developed to resolve the mentioned problems and meet the requirements of future applications of Mg-Al alloys. Semi-solid metal (SSM) processing is a promising manufacturing route capable of producing castings with a high level of complexity. 21,22 The main advantage of SSM processing, compared to the conventional casting processes, is the possibility to have a laminar flow of metal during mold filling.23 This is a consequence of the higher viscosity of the semi-solid material, and it reduces air entrapment compared to die-casting. This results in components with enhanced microstructural proper...

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“…Localized corrosion has been studied for decades, and the current understanding of the mechanisms and critical factors has been reported. [9][10][11][12][13][14][15] In the case of resin powder-coated carbon steels, susceptibility to corrosion is correlated to the properties of each protective layer, and the bonding conditions between different layers, as shown in Fig. 1.…”

Section: Coating and Coating Damage Caused Corrosion And Cracking Of mentioning

confidence: 99%

An Industrial Perspective on Environmentally Assisted Cracking of Some Commercially Used Carbon Steels and Corrosion-Resistant Alloys

Ashida¹,

Daigo

Sugahara

2017

JOM

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Commercial metals and alloys like carbon steels, stainless steels, and nickelbased super alloys frequently encounter the problem of environmentally assisted cracking (EAC) and resulting failure in engineering components. This article aims to provide a perspective on three critical industrial applications having EAC issues: (1) corrosion and cracking of carbon steels in automotive applications, (2) EAC of iron-and nickel-based alloys in salt production and processing, and (3) EAC of iron-and nickel-based alloys in supercritical water. The review focuses on current industrial-level understanding with respect to corrosion fatigue, hydrogen-assisted cracking, or stress corrosion cracking, as well as the dominant factors affecting crack initiation and propagation. Furthermore, some ongoing industrial studies and directions of future research are also discussed.

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Understanding localized corrosion

Cited by 210 publications

References 32 publications

Localized Corrosion: Passive Film Breakdown vs. Pit Growth Stability: Part III. A Unifying Set of Principal Parameters and Criteria for Pit Stabilization and Salt Film Formation

Localized Corrosion: Passive Film Breakdown vs. Pit Growth Stability: Part III. A Unifying Set of Principal Parameters and Criteria for Pit Stabilization and Salt Film Formation

Atmospheric Corrosion of Mg Alloy AZ91D Fabricated by a Semi-Solid Casting Technique: The Influence of Microstructure

An Industrial Perspective on Environmentally Assisted Cracking of Some Commercially Used Carbon Steels and Corrosion-Resistant Alloys

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