Effects of vacuum and ageing on Zr4/Cr3 based conversion coatings on aluminium alloys

Thirupathi, Kalaivanan; Bárczy, Pál; Vad, K.; Csík, A.; Somosvári, Béla M.

doi:10.1016/j.apsusc.2018.02.092

Cited by 7 publications

(4 citation statements)

References 10 publications

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“…Interestingly, the same coating over another sample that is exposed to high vacuum ( Figure 3) reveals a slight drop in Cr, O and Al curves with complete disappearance of the Zr in the coating. Comparing Figure 2 and Figure 3 the disappearance of the second peak is probably result of tremendous shrinkage in the coating after vacuum exposure [14]. We interpret this phenomenon by assuming that the coating has two different phases.…”

Section: B Glow Discharge Optical Emission Spectroscopy (Gd-oes)mentioning

confidence: 74%

Growth Kinetics and Structure of Zr4/Cr3 Based Conversion Coating over Aluminium

Thirupathi¹,

Bárczy²,

Lassú³

2016

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In this study, the structure of Zr4/Cr3 based conversion coating on aluminium alloys was studied by using the Glow Discharge-Optical Emission Spectroscopy (GD-OES) method. Samples were examined before and after exposure to high vacuum. The results revealed that the structure of the coating has two different phases, solute and gelatinous state. The growth kinetics of conversion coating is investigated by considering the thickness of the coating under various immersion times inside the coating bath. The present data suggest that coating growth kinetics has five different states, namely activation, linear growth, limited growth, saturation limit and detachment state. The conversion coating structure over aluminium alloys such as AA2024 and AA6082 was investigated in detail to understand the influence of the substrate in coating formation. The results imply that the formation mechanism strongly depends on alloying elements of the substrate. Conversion layer growth involves dissolution and deposition of ions. It was found that the alloying elements have a slowdown influence on aluminium dissolution. The results imply that high alloyed aluminium tends to form a coating with less thickness and lower Zr-Cr concentration.

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Section: B Glow Discharge Optical Emission Spectroscopy (Gd-oes)mentioning

confidence: 74%

Growth Kinetics and Structure of Zr4/Cr3 Based Conversion Coating over Aluminium

Thirupathi¹,

Bárczy²,

Lassú³

2016

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“…An effective approach to increase the corrosion resistance of Al alloys is to fabricate coating layers on the surface to create barriers against direct corrosive attacks. Commercial anticorrosion coatings for Al alloys include electroplating [6], chemical conversion coating [7,8], and anodizing coatings [9,10]. Among them, anodizing coatings have the most widespread industrial application because of their ease of processing and low cost [11,12,13,14,15].…”

Section: Introductionmentioning

confidence: 99%

Promoted Anodizing Reaction and Enhanced Coating Performance of Al–11Si Alloy: The Role of an Equal-Channel-Angular-Pressed Substrate

et al. 2019

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In this paper, the effect of the equal-channel-angular-pressed (ECAPed) substrate on the coating formation and anticorrosion performance of the anodized Al–11Si alloy was systematically investigated. The ECAP process dramatically refines both Al and Si phases of the alloy. The parallel anodizing circuit is designed to enable a comparative study of anodizing process between the cast and the ECAPed alloys by tracking their respective anodizing current quota. The optimum coatings of both alloys were obtained after anodization for 30 min. The ECAPed alloy attained a thicker, more compact, and more uniform coating. Energetic crystal defects in the fine Al grains of the ECAPed substrate promote the anodizing reaction and lead to the thicker coating. Fragmented and uniformly distributed fine Si particles in the ECAPed alloy effectively suppress the coating cracks, enhancing the compactness of the coating. Overall, the ECAP-coated sample exhibits the best anticorrosion performance, which is evidenced by the concurrently enhanced prevention of coating and improved corrosion resistance of the substrate.

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“…Even the corrosion resistance of UFG pure Al is still insufficient. Anticorrosion coatings are effective for protecting the Al matrix against corrosion, such as electroplating [27], chemical conversion coating [28,29], and anodizing coating [30,31]. Among these, anodizing coating is the most widely used industrial technology in the corrosion protection of Al and Al alloys because of its low cost and high protection efficiency [32].…”

Section: Introductionmentioning

confidence: 99%

Effect of Ultrafine Grains on the Coating Reaction and Anticorrosion Performance of Anodized Pure Aluminum

et al. 2020

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This work analyzes the effects of ultrafine aluminum (Al) grains on the anodizing coating reaction and anticorrosion performance of anodized industrial pure Al. Equal-channel angular pressing (ECAP) was applied to cast pure Al continuously for 16 passes at room temperature, and its average grain size was dramatically refined to about 1.5 μm. The ultrafine-grain (UFG) pure Al was further anodized with a cast sample via a parallel anodizing circuit at a constant total input current. Benefited by the higher volume fraction of grain boundaries and higher internal energy of the UFG substrate, the anodizing process of the ECAP-processed pure Al was significantly accelerated, showing a more intense initial anodizing reaction, a faster initial coating thickening, and much earlier porous-layer formation compared to the cast sample. As the anodizing reaction continued, the newly formed thicker coating of the ECAP-coated sample significantly hindered the diffusion process, weakening the thermodynamic advantage and decreasing the anodizing current of the ECAP-processed sample. During the entire anodizing duration, the ECAP-processed pure Al experienced gradually decreased anodizing current, while the cast sample experienced increased anodizing current. Because of the more total reaction, the ECAP-coated sample always maintained a relatively thicker coating and better anticorrosion performance during the entire anodizing duration.

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Effects of vacuum and ageing on Zr4/Cr3 based conversion coatings on aluminium alloys

Cited by 7 publications

References 10 publications

Growth Kinetics and Structure of Zr4/Cr3 Based Conversion Coating over Aluminium

Growth Kinetics and Structure of Zr4/Cr3 Based Conversion Coating over Aluminium

Promoted Anodizing Reaction and Enhanced Coating Performance of Al–11Si Alloy: The Role of an Equal-Channel-Angular-Pressed Substrate

Effect of Ultrafine Grains on the Coating Reaction and Anticorrosion Performance of Anodized Pure Aluminum

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