Stability of the anodic film on aluminium in relation to the nature of some anions

Ammar, I. A.; Darwish, S.; Ammar, E. A.

doi:10.1002/maco.19730240304

Cited by 4 publications

(1 citation statement)

References 17 publications

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“…Phosphate ions are reported [164,[317][318][319][320] to form stable oxide layers that inhibit hydration reactions in wet environments. Thus, the presence of phosphate ions in/on the unsealed anodic oxide layer or in the sealing bath electrolyte is likely to retard the kinetics of the sealing step by suppressing hydration processes [157,164,205,206,[321][322][323]. This tendency has indeed been confirmed in various reports [37,324,325].…”

Section: Effect Foreign Anions and Cations On The Crystallization Of mentioning

confidence: 83%

The Sealing Step in Aluminum Anodizing: A Focus on Sustainable Strategies for Enhancing Both Energy Efficiency and Corrosion Resistance

2020

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Increasing demands for environmental accountability and energy efficiency in industrial practice necessitates significant modification(s) of existing technologies and development of new ones to meet the stringent sustainability demands of the future. Generally, development of required new technologies and appropriate modifications of existing ones need to be premised on in-depth appreciation of existing technologies, their limitations, and desired ideal products or processes. In the light of these, published literature mostly in the past 30 years on the sealing process; the second highest energy consuming step in aluminum anodization and a step with significant environmental impacts has been critical reviewed in this systematic review. Emphasis have been placed on the need to reduce both the energy input in the anodization process and environmental implications. The implications of the nano-porous structure of the anodic oxide on mass transport and chemical reactivity of relevant species during the sealing process is highlighted with a focus on exploiting these peculiarities, in improving the quality of sealed products. In addition, perspective is provided on plausible approaches and important factors to be considered in developing sealing procedures that can minimize the energy input and environmental impact of the sealing step, and ensure a more sustainable aluminum anodization process/industry.Coatings 2020, 10, 226 2 of 55 sealing methods. Furthermore, the applicability of another hitherto popular sealing process; chromate sealing, is currently limited to essential parts in the aerospace industry due to toxicological, health, and environmental implications traced to Cr(VI) employed in the process [7][8][9][10][11][12][13][14][15][16]. On the other hand, the advantages of another industrially utilized sealing process; the nickel fluoride (cold) sealing process is limited by the toxicity of nickel salts which narrows its range of application, and introduces added costs due to post-sealing wastewater treatments and management [17][18][19][20]. Further efforts at sealing anodized aluminum at temperatures lower than that used in hydrothermal (high temperature) sealing, have led to much variety in the chemical constitution and operating temperatures of sealing baths [21]. On the basis of temperature at which the sealing step is carried out, sealing can be classified into three major categories; high temperature, mid-temperature, and room-temperature or cold sealing. In this work sealing at temperatures from 0 to 40 • C is classified as low temperature sealing, from ≥ 40 • C to 70 • C as intermediate or mid temperature sealing, and sealing at temperatures > 70 • C as high temperature sealing.

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Section: Effect Foreign Anions and Cations On The Crystallization Of mentioning

confidence: 83%

The Sealing Step in Aluminum Anodizing: A Focus on Sustainable Strategies for Enhancing Both Energy Efficiency and Corrosion Resistance

2020

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Galvanostatic formation of barrier‐type Anodic oxides

Ammar

Darwish

Khalil

1981

Materialwissenschaft Werkst

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Experimental Factors Affecting Oxide Growth Results of galvanostatic anodization of various metals with varying valve‐metal behaviour including Nb, Ta, Zr, Ti, Al, W, Te, Sb, and Bi are compiled and compared with respect to the effect of various experimental factors such as surface pretreatment, stirring, solution composition, temperature of the bath, on the efficiency of oxide growth relative to that for other anodic processes. It is concluded that all of the above factors play an important role in the anodization of the non‐typical valve metals, particularly Sb, Bi and W. Typical anodic charging curves associated with the process of oxide growth are given for several valve metals. Experimental data relevant to the phenomena of oxide breakdown are recorded and compared. The results indicate that the mechanism of breakdown varies for the same metal with variations in the experimental conditions.

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Galvanostatic formation of barrier‐type Anodic oxides. Simplified theory of anodization

Ammar

Darwish

Khalil

1981

Materialwissenschaft Werkst

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A comprehensive presentation of the theory of galvanostatic anodization has been given in order to enable interpretation and prediction of the anodization behaviour of barrier layers during technical work on various value metals. The following parameters have been considered, and the relations between them have been established: oxide formation rate, reciprocal capacity, electric field strength, pre‐polarization oxide thickness, interfacial potentials, the height and width of energy barrier for ion transport in the oxide phase, the oxide growth rate as derived from the dependence of cd on time under constant potential, and capacity. Furthermore, it has been demonstrated that potentiostatic curves can be derived from galvanostatic results, and the derived curves are similar to those directly measured by the potentiostatic technique. The theory has been satisfactorily applied to the experimental results based on the anodic charging curves and other complementary measurements on a large number of valve metals including Nb, Ta, Zr, Ti, Al, W, Te, Sb, and Bi.

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Stability of the anodic film on aluminium in relation to the nature of some anions

Cited by 4 publications

References 17 publications

The Sealing Step in Aluminum Anodizing: A Focus on Sustainable Strategies for Enhancing Both Energy Efficiency and Corrosion Resistance

The Sealing Step in Aluminum Anodizing: A Focus on Sustainable Strategies for Enhancing Both Energy Efficiency and Corrosion Resistance

Galvanostatic formation of barrier‐type Anodic oxides

Galvanostatic formation of barrier‐type Anodic oxides. Simplified theory of anodization

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