Localized electrochemical study of corrosion inhibition in microdefects on coated AZ31 magnesium alloy

Karavai, O.V.; Bastos, A.C.; Zheludkevich, Mikhail L.; Taryba, Maryna; Lamaka, Sviatlana V.; Ferreira, M.G.S.

doi:10.1016/j.electacta.2010.04.064

Cited by 125 publications

(63 citation statements)

References 43 publications

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“…This result is in agreement with data reported by K. Fukumura and O. V. Karavai, where 1,2,4-triazole was described as inhibitor that reduced corrosion attack of Mg thought sol-gel coatings. 43,44 The designed in this work self-healing composite coating might be utilized for active protection of magnesium components that are exposed to both aggressive media and (or) mechanical impact. Formation of thin PEO coating (1.8 mm) is considerably less energy consuming than growing traditional thick PEO (>20 mm).…”

Section: Protective Behavior Of Composite Coatingsmentioning

confidence: 99%

“…Coated surfaces of Mg alloy AZ31 were reported to be analyzed by SVET at articial needle-defect zones. 44,51 SVET was also used for quantitative evaluation of "self-healing" effects of corrosion inhibitor when it is distributed in protective coating deposited on a metal surface. 52 Articial defects simulate the coating damage as might occur during its service-life.…”

Section: Protective Behavior Of Composite Coatingsmentioning

confidence: 99%

“…In the present work we report that even thin PEO coatings (1.8 mm) formed in so "spark" anodizing regime, combined with appropriate inhibitor and sealant is sufficient for providing lasting active protection to Mg alloy. The coating consists of a porous PEO formed oxide layer loaded with corrosion inhibitor, 1,2,4-triazole, 43,44 and a layer of sol-gel sealant. Anodic lm serves as an additional intermediate barrier between the Mg alloy and the sol-gel sealant.…”

Section: Introductionmentioning

confidence: 99%

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Active corrosion protection coating for a ZE41 magnesium alloy created by combining PEO and sol–gel techniques

et al. 2016

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An active protective coating for ZE41 magnesium alloy was produced by sealing an anodic layer, loaded with 1,2,4-triazole, with a sol-gel film. An anodic oxide layer was formed using PEO in a silicate-fluoride alkaline solution. This thin (1.8 mm) porous PEO layer was impregnated with corrosion inhibitor 1,2,4-triazole and sealed with a silica-based sol-gel film modified with titanium oxide. For the first time it was demonstrated that this relatively thin PEO-based composite coating revealed high barrier properties and provided superior protection against corrosion attack during 1 month of continuous exposure to 3% NaCl. A scanning vibrating electrode technique showed a sharp decrease (100 times) of corrosion activity in micro defects formed in the 1,2,4-triazole doped composite coating, when compared to blank samples.

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Section: Protective Behavior Of Composite Coatingsmentioning

confidence: 99%

Section: Protective Behavior Of Composite Coatingsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Active corrosion protection coating for a ZE41 magnesium alloy created by combining PEO and sol–gel techniques

et al. 2016

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“…15,17 The potentiometric mode of SECM has also been extensively employed to characterize both pHs and Mg 2+ flux during corrosion of Mg alloys. 16,18,[33][34][35] The Mg 2+ is generated by anodic oxidation of the matrix phase (Equation 1) while the reduction of water occurs predominantly on the more noble alloy constituents (secondary phases) producing dissolved molecular H 2 and OH − species (Equation 2). Generation of OH − in the cathodic reaction leads to localized pH changes and the deposition of Mg(OH) 2 (Equation 3) on the alloy surface (K sp, Mg(OH) 2 = 5.61 × 10 −12 ).…”

mentioning

confidence: 99%

“…15,17 The potentiometric mode of SECM has also been extensively employed to characterize both pHs and Mg 2+ flux during corrosion of Mg alloys. 16,18,[33][34][35] …”

mentioning

confidence: 99%

Local Hydrogen Fluxes Correlated to Microstructural Features of a Corroding Sand Cast AM50 Magnesium Alloy

Dauphin‐Ducharme

Asmussen

Tefashe

et al. 2014

J. Electrochem. Soc.

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Successful in situ spatiotemporal tracking of corrosion processes occurring at heterogeneous Mg alloy microstructures was achieved through tandem analyses involving electron and electrochemical microscopies. Through cross-correlation of scanning electron microscopy and scanning electrochemical microscopy images and subsequent analytical transmission electron microscopy, the morphology and chemical composition of microstructural components on the surface of a sand-cast AM50 Mg alloy were related to their respective local evolution of H 2 with micron scale resolution prior to, during and post corrosion. The results confirm that the preferential water reduction sites in the initial stages of corrosion are the Al 8 Mn 5 intermetallics while a β-Mg 17 Al 12 precipitate contaminated with Ni becomes cathodically active at a later stage of corrosion. This approach demonstrates the power of correlative approaches to probe and understand local electrochemical phenomena. Owing to their light weight, high strength-to-weight ratio, good castability and high damping capacity, Mg alloys are ideal candidates for automotive structural components.1-5 The compromise of formability, room temperature ductility and price represent major challenges in commercializing these materials. Importantly, Mg alloys also suffer from poor corrosion resistance in aqueous environments 6-8 and due to their positions in the electrochemical activity series, are highly susceptible to accelerated corrosion rates when in galvanic contact with a more noble material.9 At open circuit, the overall galvanic current is null due to a balance between the anodic and cathodic current densities, while on a microscopic scale, a difference in electrochemical potential is obtained. In Mg alloys, galvanic coupling between microstructural components of the alloy (commonly referred to as microgalvanic coupling) stems from an inherent electrochemical potential difference between the Mg matrix and its secondary phases, [10][11][12] and can be tracked using local scanning probe methods.Local scanning probe techniques such as several modes of scanning electrochemical microscopy (SECM), [13][14][15][16][17][18][19] scanning Kelvin probe force microscopy (SKPFM), 20-22 the scanning vibrating electrode technique (SVET) [23][24][25] and local electrochemical impedance spectroscopy (LEIS) 26 have been used to probe the heterogeneous surfaces of Mg alloys and to assess the electrochemical behavior of the different microstructural constituents responsible for microgalvanic corrosion. Among these techniques, SECM has the ability to quantify electrochemical fluxes in situ with high lateral resolution using a microelectrode (ME). 27 This technique has been successfully applied in corrosion research to provide in situ analyses of pitting corrosion at oxide films, [28][29][30] to assess lateral variations in corrosion kinetics, 31 and to detect defects within coated metal samples. 32The feedback mode of SECM has been employed to probe corroding AM60 15 and AZ31 17 Mg alloys. The incre...

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Local pH and Its Evolution Near Mg Alloy Surfaces Exposed to Simulated Body Fluids

Lamaka

González

Mei

et al. 2018

Adv Materials Inter

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Many reports are available on degradation rates and corrosion product characterization of magnesium alloys for implant application. Typically, the data are obtained ex situ, as post factum analysis of occurred degradation processes or in bulk electrolyte that does not fully reflect concentration gradients at the interface and in the diffusion layer. Meanwhile, these local conditions are essential for tissue‐implant compatibility. Only a limited number of studies employ the techniques that visualize ongoing degradation and are localized enough to observe the changes in the electrolyte layer directly adjacent to corroding magnesium. Here, local pH in Hank's solution is studied in operando, with potentiometric micro‐probes (d = 2 µm) located 10–50 µm above the surface of four Mg alloys potentially relevant for implant applications. A significant difference in local pH is observed for Mg in simple Hank's solution (near surface pH 9.9–10.5) or Hank's solution modified with 2.5 × 10−3 m Ca2+ (pH 7.8–8.5). The corresponding pH values are established during the first seconds of immersion. These findings indicate different degradation kinetics in electrolytes with or without Ca2+. The degradation rate of Mg alloys decreases by almost two times in Ca2+ containing Hank's solution. Calcium‐phosphate/carbonate protective layer stabilizes the surface pH below 8.5 controlling Mg degradation.

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Localized electrochemical study of corrosion inhibition in microdefects on coated AZ31 magnesium alloy

Cited by 125 publications

References 43 publications

Active corrosion protection coating for a ZE41 magnesium alloy created by combining PEO and sol–gel techniques

Active corrosion protection coating for a ZE41 magnesium alloy created by combining PEO and sol–gel techniques

Local Hydrogen Fluxes Correlated to Microstructural Features of a Corroding Sand Cast AM50 Magnesium Alloy

Local pH and Its Evolution Near Mg Alloy Surfaces Exposed to Simulated Body Fluids

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