FESEM and EIS Study of Sealed AA2024 T3 Anodized in Sulfuric Acid Electrolytes: Influence of Tartaric Acid

Boisier, Grégory; Pébère, Nadine; Druez, Catherine; Villatte, Martine; Suel, Stéphane

doi:10.1149/1.2969277

Cited by 101 publications

(111 citation statements)

References 40 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…[4][5][6] The restriction on the use of chromium Cr (IV) compounds has also led to the development of alternative chromium-free anodizing methods, including the sulfuric-tartaric process (TSA), a typical anodizing method used in aerospace industries. [7][8][9][10] In simple terms, the anodizing process is used to obtain a thick aluminum oxide layer with a porous structure, whereas the sealing process is used to close the pores with hydrated products, thereby further increasing the corrosion resistance. A detailed discussion of the complex effects of pore morphology, film thickness, sealing time and nature of the sealing solution can be found elsewhere and it is not reported in detail here.…”

mentioning

confidence: 99%

Development of a Chromium-Free Post-Anodizing Treatment Based on 2-Mercaptobenzothiazole for Corrosion Protection of AA2024T3

Yang¹,

Yang²,

Balaskas³

et al. 2017

J. Electrochem. Soc.

View full text Add to dashboard Cite

The anticorrosion performance provided by new anodizing and sealing methods for the AA2024T3 aluminum alloy is discussed in this work. Two anti-corrosion post-anodizing treatments based on immersion in an ethanol solution containing 2-mercapto-benzothiazole (2-MBT) were applied. Both treatments consisted of the immersion of the anodized specimens in 2-MBT ethanol solution, but the second was followed by hydrothermal sealing in water. Electrochemical Impedance Spectroscopy (EIS) and an immersion test show that both treatments exhibited improved corrosion resistance compared with anodized AA2024-T3 that was only hot water sealed. Considering that these novel anti-corrosion methods appear to provide enhanced, long-term and stable corrosion resistance to the AA2024T3 aluminum alloy, the use of 2-mercaptobenzothiazole (2-MBT) is proposed as a promising inhibitor in sealing treatments. AA2024T3 aluminum alloy is widely used in the aerospace industry due to its high strength to weight ratio.1 However, high amounts of copper, together with magnesium and other alloying elements, generate second-phase particles that cause microgalvanic coupling in the presence of moisture or aqueous electrolyte, thereby reducing corrosion resistance.Anodizing is an electrochemical method that converts the aluminum surface into a corrosion-resistant, durable oxide layer with a porous structure. The pore diameter, thickness, structure and morphology of the oxide layer depend on the applied anodizing conditions, such as anodizing potential, temperature and electrolyte.2 Traditionally, anodizing of aluminum alloys is usually performed in chromic acid electrolytes, and it is followed by sealing in dichromate solution. However, as a result of its toxicity, 3 legislation will severely restrict the use of sodium dichromate, which has led to the development of alternative dichromate-free sealing treatments. [4][5][6] The restriction on the use of chromium Cr (IV) compounds has also led to the development of alternative chromium-free anodizing methods, including the sulfuric-tartaric process (TSA), a typical anodizing method used in aerospace industries. [7][8][9][10] In simple terms, the anodizing process is used to obtain a thick aluminum oxide layer with a porous structure, whereas the sealing process is used to close the pores with hydrated products, thereby further increasing the corrosion resistance. A detailed discussion of the complex effects of pore morphology, film thickness, sealing time and nature of the sealing solution can be found elsewhere and it is not reported in detail here.11-15 Different types of sealing methods have been studied, including dichromate sealing, hot water sealing, and nickel acetate sealing. 16 Commonly quoted sealing treatments are hot water or aqueous nickel acetate, but neither is as good as hexavalent chromiumbased processes; moreover, both are energy consuming as the sealing takes place at 95• C. In addition, new sealing techniques such as cerium sealing have been developed during the last decade, 10,[17][18...

show abstract

mentioning

confidence: 99%

Development of a Chromium-Free Post-Anodizing Treatment Based on 2-Mercaptobenzothiazole for Corrosion Protection of AA2024T3

Yang¹,

Yang²,

Balaskas³

et al. 2017

J. Electrochem. Soc.

View full text Add to dashboard Cite

show abstract

“…It was concluded that the presence of tartaric acid results in the formation of anodic films with lower porosity than those produced by DSA anodizing. The EIS study revealed that corrosion resistance of sealed anodize film in TSA is significantly better than the sealed film obtained by DSA anodizing which is mainly associated with the higher compactness of the porous layer and higher resistance of the hydrothermallysealed barrier layer [6].…”

Section: Introductionmentioning

confidence: 90%

“…Anodizing in dilute sulphuric acid (DSA) is performed to obtain thin anodize layer (1 -5 µm) that gives lower impact on the fatigue strength of the alloy. However, despite an improvement of fatigue strength of the alloy, its corrosion resistance is still lower than the alloy being anodized in CA [6].…”

Section: Introductionmentioning

confidence: 95%

“…It was reported that tartaric acid forms residue in pore solution of the anodize film which limits anodic reaction of aluminium dissolution in nearly neutral, chloride-rich environment [7]. Boisier et al [6] have conducted FESEM and EIS study of sealed AA2024 T3 alloy anodized in sulphuric acid electrolyte to investigate the influence of tartaric acid on anodic film morphology and on corrosion resistance of hydrothermally sealed anodized alloy. It was concluded that the presence of tartaric acid results in the formation of anodic films with lower porosity than those produced by DSA anodizing.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Effects of Anodizing Parameters in Tartaric-Sulphuric Acid on Coating Thickness and Corrosion Resistance of Al 2024 T3 Alloy

Mubarok¹,

Wahab²,

Sutarno³

et al. 2015

JMMCE

View full text Add to dashboard Cite

Abstract2024 T3 is one of aluminium alloys which are widely used in the aircraft structures. Anodizing of alluminium alloy in tartaric-sulphuric acid (TSA) electrolyte is developed to obtain more environmentally-friendly process and to produce anodize layer with better corrosion resistance. In this research work, the influences of anodizing parameters of Al 2024 T3 in TSA on the thickness, weight and corrosion resistance of the anodize layer are studied. Corrosion resistance test was carried out by conducting salt spray test for 336 hours and anodic polarization measurements using potentiostat. Results of three-factor analysis of variance (ANOVA) demonstrated that the most influencing factor that determines the thickness and weight of the anodize layer is temperature, followed by applied voltage, duration of anodizing, voltage-temperature interaction, interaction of temperature-duration of anodizing, interaction of voltage-temperature-duration of anodizing, and interaction of voltage and duration of anodizing. The pit density and corrosion current density (icorr) were found to be dependent on the coating thickness. The anodize layer with a thickness of higher than 3 μm was not experienced to pitting corrosion during 336 hours of salt spray test.

show abstract

“…35,37,41 Further, on more complex potential-time cycles, typical of industrial practice and resulting in morphologies that vary across the film thickness, the sealing behavior still requires investigation.…”

Section: C908mentioning

confidence: 99%

Cerium-Based Sealing of Anodic Films on AA2024T3: Effect of Pore Morphology on Anticorrosion Performance

Carangelo

Curioni

Acquesta

et al. 2016

J. Electrochem. Soc.

View full text Add to dashboard Cite

In this work, porous anodic oxides were produced by traditional and modified tartaric sulfuric anodizing (TSA) processes and sealed in hot water, chromate and cerium based solutions. The sealing behavior of a film with relatively coarse porosity, generated at high voltage (traditional TSA), was compared to the sealing behavior of a film with finer porosity and generated at reduced potential (modified TSA). After sodium chromate sealing, the two anodizing cycles produced film with similar anticorrosion performance. Conversely, after hot water or cerium sealing, the finer oxides generated at low voltage (modified TSA) provided much better corrosion resistance. EIS performed in-situ during sealing revealed that chromate sealing is very aggressive to the porous skeleton compared to the other sealing treatments. Therefore, the original morphology has little effect on the final performance, since both fine and coarse oxides are substantially attacked. In contrast, the oxide morphology has a substantial effect when sealing is performed in hot water or cerium-based solution. Overall, it is possible to obtain films with anticorrosion performance equivalent or improved compared to that obtained by traditional TSA anodizing cycle sealed with chromate by combining the low voltage anodizing cycle with the cerium-based sealing. Aerospace aluminum alloys display outstanding mechanical properties but require specific protection measures in order to meet the requirements of durability and corrosion resistance. Anodizing in acidic electrolytes is one of the methods that are most widely employed for this purpose, since it produces porous oxides that improve corrosion resistance and adhesion with organic coatings.The porous anodic oxide morphology generated on high copper alloys is significantly different from that generated on high purity aluminium.1-3 Specifically, on aluminum, anodizing in phosphoric, sulfuric, or oxalic acid, results in the generation of a well-ordered oxide morphology, comprising closely-packed hexagonal cells with a central cylindrical pore, and having a diameter that is proportional to the applied potential.4-10 Under these conditions, the pore walls are generally straight and uniform (provided that anodizing is conducted under steady applied potential or current). At the bottom of the pores, close to the metal, a barrier layer is observed with thickness proportional to the applied potential. On the other hand, the thickness of the porous oxide is proportional to the charge passed. Due to the dependence of barrier layer thickness and pore diameter on the applied potential, and to the dependence of the film thickness on charge, porous morphologies can be tailored by controlling the electrical regime (potential-time or current-time), and complex morphologies can be achieved to enhance specific properties.11-14 It has been shown that fine pores and thick films are beneficial for corrosion protection.13 However fatigue life can be an issue for aerospace alloys 15 and therefore film thickness should be limited to...

show abstract

FESEM and EIS Study of Sealed AA2024 T3 Anodized in Sulfuric Acid Electrolytes: Influence of Tartaric Acid

Abstract: OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. This is an author-deposited version published in: http://oatao.univ-toulouse.fr/ Eprints ID : 2407To link to this article : URL : http://dx.

Cited by 101 publications

References 40 publications

Development of a Chromium-Free Post-Anodizing Treatment Based on 2-Mercaptobenzothiazole for Corrosion Protection of AA2024T3

Development of a Chromium-Free Post-Anodizing Treatment Based on 2-Mercaptobenzothiazole for Corrosion Protection of AA2024T3

Effects of Anodizing Parameters in Tartaric-Sulphuric Acid on Coating Thickness and Corrosion Resistance of Al 2024 T3 Alloy

Cerium-Based Sealing of Anodic Films on AA2024T3: Effect of Pore Morphology on Anticorrosion Performance

Contact Info

Product

Resources

About