Corrosion protective properties of nanostructured sol–gel hybrid coatings to AA2024-T3

Zheludkevich, Mikhail L.; Serra, R.; Montemor, M.F.; Salvado, Isabel M. Miranda; Ferreira, M.G.S.

doi:10.1016/j.surfcoat.2004.09.007

Cited by 268 publications

(141 citation statements)

References 19 publications

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“…Similar phenomena reported in the literature have been ascribed to an intermediate oxide layer formed on alloy/sol-gel coating interface by Si-O-Al bonds, respectively [25]. The data indicates that the 0.5% and 0.7% Mg systems maintain high phase angle ( § RYHr the mid frequency range, implying superior barrier properties when compared to the other coatings.…”

Section: Fig 2 (A) and (B)supporting

confidence: 85%

Influence of magnesium nitrate on the corrosion performance of sol–gel coated AA2024-T3 aluminium alloy

Varma¹,

Duffy

Cassidy³

2009

Surface and Coatings Technology

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Traditional anti-corrosion technology has relied heavily on using reducible metal species, predominantly hexavalent chromium (Cr(VI)), for protecting reactive metal alloys such as aluminium which is extensively used in the aerospace sector. However, the impending changes in the use of Cr(VI) in Europe and the United States have forced aerospace manufacturers to examine alternative materials for protecting aluminium. One of the most promising alternatives being investigated are organosilane based sol-gels containing anticorrosion additives. In this work the anti-corrosion properties of magnesium (II) nitrate (Mg(NO 3 ) 2 ) as a inhibitor was investigated at different concentrations (0.1% -1.0 wt %) in a methyltriethoxysilane (MTEOS) sol-gel on the aluminium alloy AA 2024-T3 and compared to Alodine TM 1200 (the established Cr(VI) pre-treatment). Electrochemical evaluation of the coating system by electrochemical impedance spectroscopy (EIS) and potentiodynamic scanning (PDS) measurements correlated strongly with results obtained from Neutral Salt Spray (NSS) exposure data. The surface morphology of the coating was studied using atomic force microscopy (AFM) and scanning electron microscopy (SEM). The results indicated the optimum performance was achieved using a Mg (NO 3 ) 2 . level of 0.7% w/w. It is proposed that the superior anticorrosion properties of the Mg 2+ rich sol-gel is due to the pore blocking mechanism of insoluble Mg(OH) 2 formed during the hydrolysis process.

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Section: Fig 2 (A) and (B)supporting

confidence: 85%

Influence of magnesium nitrate on the corrosion performance of sol–gel coated AA2024-T3 aluminium alloy

Varma¹,

Duffy

Cassidy³

2009

Surface and Coatings Technology

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“…We can also underline, on Bode diagram, relative to phase angle evolutions, a phenomenon at high frequencies (%10 3 Hz), associated with both capacitance and resistance of alumino-silane hybrid coating [5,[32][33][34][35][36]. The high angle values, closed to 908, suggest an efficient barrier effect whatever the cerium concentration of the coatings.…”

Section: Morphological Characterization Of the Filmmentioning

confidence: 78%

“…This hypothesis can be confirmed by the presence of another phenomenon, noted at low frequencies (%10 À1 Hz) on the phase angle evolution for the two higher cerium concentrations (0.05 and 0.1 M). Indeed, this new time constant can be correlated to the presence of the corrosion activity on the substrate [4,5,36,13,[39][40][41]. It is possible to note that the phenomenon is more important for the higher values of cerium concentration (0.1 M).…”

Section: Morphological Characterization Of the Filmmentioning

confidence: 83%

“…Consequently, it is necessary to develop new environmentally compliant chromate (VI)-free alternatives. A new promising approach consists to use sol-gel process to prepare hybrid protective coatings [4,5]; thus, sol-gel films were highly investigated from the last decade as possible candidates for environmentally friendly treatments on metals [5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

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Effect of cerium on structure modifications of a hybrid sol–gel coating, its mechanical properties and anti-corrosion behavior

Cambon

Esteban

Ansart

et al. 2012

Materials Research Bulletin

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“…15 The corrosion of AA2024-T3 in 3% NaCl was reduced when coatings containing 20 mol% ZrO 2 were applied. 34 ZrO 2 nanoparticles were also formed with other chelating reagents, such as acetylacetone, 2,2 -bipyridine and 3,4-diaminobenzoic acid. 19,20,23 The degree of corrosion protection depends on the type of chelating agent used.…”

mentioning

confidence: 99%

Electrochemical and Salt Spray Testing of Hybrid Coatings Based on Si and Zr Deposited on Aluminum and Its Alloys

Rodič

Milošev

2015

J. Electrochem. Soc.

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Hybrid coatings based on Si and Zr were assessed for their protection of aluminum and its alloys 2024-T3 and 7075-T6 against corrosion in 0.5 M NaCl. Coatings were prepared from sol synthesized from mixtures of tetraethyl orthosilicate and 3-methacryloxypropyl trimethoxysilane to which various concentrations of zirconium tetrapropoxide and methacrylic acid were added. Short-and long-term electrochemical behavior was assessed. The degree of protection was dependent on the sol composition, ageing time and curing temperature. A coating containing Zr/Si ratio of 0.41, aged for 48 h and cured at 100 • C exhibited the best combination of resistance towards general and localized corrosion. Electrochemical parameters obtained under polarization (corrosion current density of 4.4 nA/cm 2 and stability up to 7 V), and under open circuit conditions (impedance in the few tens of Mohm cm 2 after one week immersion) prove that the protection was high. At other conditions, such as higher Zr/Si ratios, shorter ageing time or curing at room temperature, protection was excellent early after immersion but then lessened rapidly. Coatings prepared under optimal conditions provided a high degree of protection over 500 hours salt spray testing, especially on aluminum metal. These coatings have the potential to provide good protection in chloride environments. While aluminum has good corrosion resistance in seawater, its high-strength alloys in the 2xxx (Al-Cu-Mg) and 7xxx series (Al-ZnMg) are normally not recommended for use under these conditions. 1,2Since there is an ongoing need for light-weight, high-strength materials, the possibility of using alloys other than those of the series 5xxx (Al-Mg-Mn) and 6xxx (Al-Mg-Si) normally recommended for sea-coast applications has to be considered. 2,3Aluminum and its alloys are highly susceptible to oxidation, resulting in the passivation of the surface by a 0.01 to 10 μm thick oxide layer when exposed to air. This naturally formed oxide protects aluminum under atmospheric conditions.2 Passivation of the alloys is, however, less effective. Due to the presence of unevenly distributed intermetallic particles (IMPs), the passive film is, overall, thinner and less uniform. IMPs such as Al 2 CuMg, Al-Cu-Mn-Fe, Al 2 Cu, Al 3 Fe, MgSi 2 , MgZn 2 , create local galvanic cells that promote corrosion on the surface. [4][5][6] Al 2 O 3 is a good insulator but, when containing IMPs, is a semiconductor that allows limited passage of electrons.2 High concentrations of chloride ions allows localized breakdown of the aluminum oxide film, most commonly observed as pitting, crevice or galvanic corrosion.Al alloys have been protected for decades using chromate conversion coatings. In the last decade these coatings have been widely prohibited within 7 and outside 8 the EU due to the fact that hexavalent chromium is a toxic, carcinogenic and environmentally hazardous compound.9-11 Other environmentally hazardous compounds, such as volatile organic compounds (VOCs) used, for example, in the painting industry, have ...

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Corrosion protective properties of nanostructured sol–gel hybrid coatings to AA2024-T3

Cited by 268 publications

References 19 publications

Influence of magnesium nitrate on the corrosion performance of sol–gel coated AA2024-T3 aluminium alloy

Influence of magnesium nitrate on the corrosion performance of sol–gel coated AA2024-T3 aluminium alloy

Effect of cerium on structure modifications of a hybrid sol–gel coating, its mechanical properties and anti-corrosion behavior

Electrochemical and Salt Spray Testing of Hybrid Coatings Based on Si and Zr Deposited on Aluminum and Its Alloys

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