Magnesium Alloy Effects on Plasma Electrolytic Oxidation Electro-Ceramic and Electro-Coat Formation and Corrosion Resistance

Brady, Michael P.; Leonard, Donovan N.; McNally, Elizabeth A.; Kish, Joseph R.; Meyer, Harry M.; Cakmak, Ercan; Davis, Bruce

doi:10.1149/2.0531914jes

Cited by 13 publications

(8 citation statements)

References 59 publications

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“…These alloys were selected because they represent two major classes of Mg alloys and are from the same batch of coiled sheets used in a recent study by the authors. 43 Alloy compositions analyzed by inductively coupled plasma atomic emission spectroscopy (ICP-AES) are shown in Table I. 43 The samples for ICP analysis were mechanically abraded to American National Standards Institute (ANSI) 320 grit surface finish using SiC abrasive paper and tap water as a lubricant to remove all residual surface finish prior to bulk compositional analysis.…”

Section: Methodsmentioning

confidence: 99%

“…43 Alloy compositions analyzed by inductively coupled plasma atomic emission spectroscopy (ICP-AES) are shown in Table I. 43 The samples for ICP analysis were mechanically abraded to American National Standards Institute (ANSI) 320 grit surface finish using SiC abrasive paper and tap water as a lubricant to remove all residual surface finish prior to bulk compositional analysis. 42,43 Sample preparation followed practices described in Refs.…”

Section: Methodsmentioning

confidence: 99%

“…43 The samples for ICP analysis were mechanically abraded to American National Standards Institute (ANSI) 320 grit surface finish using SiC abrasive paper and tap water as a lubricant to remove all residual surface finish prior to bulk compositional analysis. 42,43 Sample preparation followed practices described in Refs. 25-27, 30 and 42. Rectangular alloy test samples ∼18 × 25 mm were electro-discharged machine (EDM) cut from 1.5 to 1.6 mm thick rolled coil sheet of AZ31B and ZE10A.…”

Section: Methodsmentioning

confidence: 99%

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Temporal Evolution of Corrosion Film Nano-Porosity and Magnesium Alloy Hydrogen Penetration in NaCl Solution

Brady

Rother

Frith

et al. 2020

J. Electrochem. Soc.

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Exposures of 0.5, 1, 4, 8, and 24 h were conducted for Mg-3Al-1Zn (AZ31B) and Mg-1.5Zn-0.3Zr-<0.5Nd (ZE10A, ZEK100 type) alloys in D2O with 5 weight% (wt%) NaCl. Multiple techniques including small angle neutron scattering (SANS) and scanning transmission electron microscopy (STEM) were used to follow the growth of nano-porous oxide-hydroxide corrosion films. On the same samples, time of flight mass spectrometry (ToF SIMS) was used to study the penetration of deuterium into the alloys in advance of the films. The SANS scattering invariants, which are proportional to the number of nanoscale features, increased approximately linearly with time for both alloys. Analysis with the polydisperse hard sphere model for fractal systems suggests that the nano-porous structures grew at all length scales assessed, but that the size distribution did not change significantly with reaction time, i.e., the film thickness increased while the nano-porosity structures remained essentially constant. Extensive penetration of deuterium into the underlying alloy was observed by ToF-SIMS for ZE10A, but not AZ31B despite similar corrosion film growth behavior. The depth profiles suggest an alloy diffusion-controlled deuterium penetration over time, which is of similar extent to that previously observed in water without NaCl. Implications for the corrosion mechanism(s) are discussed.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Temporal Evolution of Corrosion Film Nano-Porosity and Magnesium Alloy Hydrogen Penetration in NaCl Solution

Brady

Rother

Frith

et al. 2020

J. Electrochem. Soc.

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“…The application of polymeric compounds, which infiltrate the coating pores, is a common practice for anodized Mg components [ 310 ]. Research on this topic has gone in several directions, including silanes [ 274 , 311 ] and E-coatings [ 312 , 313 , 314 ]. For instance, silane treatment KH550 has been shown to enhance the corrosion resistance of a magnesium alloy with a silicate-based PEO coating [ 315 ].…”

Section: Post-treatmentmentioning

confidence: 99%

Chromate-Free Corrosion Protection Strategies for Magnesium Alloys—A Review: Part II—PEO and Anodizing

et al. 2022

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Although hexavalent chromium-based protection systems are effective and their long-term performance is well understood, they can no longer be used due to their proven Cr(VI) toxicity and carcinogenic effect. The search for alternative protection technologies for Mg alloys has been going on for at least a couple of decades. However, surface treatment systems with equivalent efficacies to that of Cr(VI)-based ones have only begun to emerge much more recently. It is still proving challenging to find sufficiently protective replacements for Cr(VI) that do not give rise to safety concerns related to corrosion, especially in terms of fulfilling the requirements of the transportation industry. Additionally, in overcoming these obstacles, the advantages of newly introduced technologies have to include not only health safety but also need to be balanced against their added cost, as well as being environmentally friendly and simple to implement and maintain. Anodizing, especially when carried out above the breakdown potential (technology known as Plasma Electrolytic Oxidation (PEO)) is an electrochemical oxidation process which has been recognized as one of the most effective methods to significantly improve the corrosion resistance of Mg and its alloys by forming a protective ceramic-like layer on their surface that isolates the base material from aggressive environmental agents. Part II of this review summarizes developments in and future outlooks for Mg anodizing, including traditional chromium-based processes and newly developed chromium-free alternatives, such as PEO technology and the use of organic electrolytes. This work provides an overview of processing parameters such as electrolyte composition and additives, voltage/current regimes, and post-treatment sealing strategies that influence the corrosion performance of the coatings. This large variability of the fabrication conditions makes it possible to obtain Cr-free products that meet the industrial requirements for performance, as expected from traditional Cr-based technologies.

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“…[4][5][6] Similar to Mg alloy AZ31B (3% Al, 1% Zn, 0.5% Mn, balance Mg), [7][8][9][10][11] corrosion of ZEK100 occurs via a localized filament-like mode that is driven by enhanced H 2 gas evolution (cathode activation) of the dissolving surface (anode activation). [12][13][14] The mode involves the initiation of local activated anodes on the filmed surface, likely at secondary phase particles that serve as cathodes. 15,16 The local activated anodes then propagate across the filmed surface driven by cathode activation, which mostly takes place at the local anode site, but with some contribution from the porous oxide/hydroxide corrosion products left behind.…”

mentioning

confidence: 99%

Corrosion Inhibition of Mg Alloy ZEK100 Sheet Metal by Dissolved Lithium Carbonate

Zaghloul

Kish

2021

J. Electrochem. Soc.

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The extent of corrosion inhibition of Mg alloy ZEK100 in 100 mM NaCl (aq) imparted by dissolved Li2CO3 (aq), with a particular focus on Li incorporation into the surface film that forms under activated anodic dissolution (anodic polarization) was determined. Dissolved Li2CO3 reduces corrosion by a factor of ∼12 when added at a concentration (100 mM) just below saturation. Effective inhibition involves suppressing the transition to filament-like corrosion, and associated anode/cathode activation, initiating at local breakdown sites. Such suppression is linked to the formation of Li-doped MgO as a corrosion product film during activated anodic dissolution. When formed by anodic polarization, the film composition also significantly affects the chloride ion distribution with the film. Without Li incorporation, chloride ions tend to enrich at the film/metal interface, whereas with Li incorporation, chloride ions tend to be uniformly distributed within the film.

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Magnesium Alloy Effects on Plasma Electrolytic Oxidation Electro-Ceramic and Electro-Coat Formation and Corrosion Resistance

Cited by 13 publications

References 59 publications

Temporal Evolution of Corrosion Film Nano-Porosity and Magnesium Alloy Hydrogen Penetration in NaCl Solution

Temporal Evolution of Corrosion Film Nano-Porosity and Magnesium Alloy Hydrogen Penetration in NaCl Solution

Chromate-Free Corrosion Protection Strategies for Magnesium Alloys—A Review: Part II—PEO and Anodizing

Corrosion Inhibition of Mg Alloy ZEK100 Sheet Metal by Dissolved Lithium Carbonate

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