Active metal-based corrosion protective coating systems for aircraft requiring no-chromate pretreatment

Bierwagen, Gordon P.; Brown, R. D.; Battocchi, Dante; Hayes, Scott A.

doi:10.1016/j.porgcoat.2009.10.031

Cited by 63 publications

(38 citation statements)

References 30 publications

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“…38,39 Magnesium-rich primer (MgRP) technology provides cathodic protection to the aluminum alloy by galvanic coupling of the metallic magnesium pigment and the aluminum alloy. 40,41 While the MgRP technology shows very promising performance, the industry still needs an alternative for chromate using the traditional leaching mechanism. Hence, the search for chromate-free inhibitor technology is continuing.…”

Section: Introductionmentioning

confidence: 99%

Lithium salts as leachable corrosion inhibitors and potential replacement for hexavalent chromium in organic coatings for the protection of aluminum alloys

et al. 2016

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Lithium salts are being investigated as leachable corrosion inhibitor and potential replacement for hexavalent chromium in organic coatings. Model coatings loaded with lithium carbonate or lithium oxalate demonstrated active corrosion inhibition and the formation of a protective layer in a damaged area during neutral salt spray exposure. The present paper provides an abridged overview of the initial studies into this novel inhibitor technology for the active corrosion protection of aluminum alloys. Coating defects were investigated by microscopic techniques before and after exposure to corrosive conditions. Scanning electron microscopy analysis of cross-sections of the coating defect area demonstrated that the protective layer comprises a typical threelayered structure, which included a dense layer near the alloy surface, a porous middle layer, and a flakeshaped out layer. Potentiodynamic polarization measurements obtained with a microcapillary cell positioned in the coating defect area and electrochemical impedance spectroscopy confirmed the corrosion protective properties of these protective layers. The longterm corrosion inhibition of the lithium-based coating technology was tested in industrial coating systems.

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Section: Introductionmentioning

confidence: 99%

Lithium salts as leachable corrosion inhibitors and potential replacement for hexavalent chromium in organic coatings for the protection of aluminum alloys

et al. 2016

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“…[47][48][49][50][51] Although many approaches have been attempted to achieve acceptable alternatives, few systems have achieved the effectiveness of chromate-containing systems. 39,46 A potential replacement for the chromate-containing pigments in organic coatings using lithium salts has been developed recently. 52,53 Neutral salt spray testing (ASTM B-117) revealed that when such pigments are added into organic coatings, the corrosion resistance increases, resulting in comparable behavior to chromate pigments.…”

mentioning

confidence: 99%

Protective Film Formation on AA2024-T3 Aluminum Alloy by Leaching of Lithium Carbonate from an Organic Coating

Liu

Visser

Zhou

et al. 2015

J. Electrochem. Soc.

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An investigation into corrosion inhibition properties of a primer coating containing lithium carbonate as corrosion inhibitive pigment for AA2024 aluminum alloy was conducted. It was found that, during neutral salt spray exposure, a protective film of about 0.2 to 1.5 μm thickness formed within the area where an artificial defect was introduced by scribing through the coating to the base alloy. This film showed a multilayered structure consisting of a relatively compact layer near the alloy substrate, a porous middle layer and a columnar outer layer. The thicknesses of the layers varied, as a consequence of the difference in the local concentration of lithium species leaching from the primer coating. The presence of the film in the scribed area significantly reduced corrosion of the alloy, with little consumption of the metal substrate within the scribed area during neutral salt spray exposure. Furthermore, the presence of the protective film resulted in a significant increase of impedance modulus, measured after the salt spray exposure.

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“…This may be due to the fact that the binder formulation employed to produce the Al slurry coating contains some Cr vl+ (<10 mg/kg) but this amount is well below the "Restriction of Hazardous Substances" (RoHS) Directive limits (1000 mg/kg) [33]. As well as Cd, chromate conversión treatments are considered a major environmental hazard for aircraft production, maintenance and repair [34], It is also important to emphasize that the Al slurry coatings do not require a dehydrogenation heat treatment, and moreover, the fatigue strength of the Al slurry-coated specimens is higher than that exhibited by the Cd plated samples despite the higher surface roughness of the Al-slurry coatings [31]. Moreover, although the effect of the Al coating applied by slurry was to decrease the axial fatigue strength of A1S1 4340 steel, the decrease in strength was lower than that observed for Cd-plated specimens.…”

Section: Discussionmentioning

confidence: 99%

Aluminum slurry coatings to replace cadmium for aeronautic applications

Agüero

Hoyo

Blas

et al. 2012

Surface and Coatings Technology

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ARTICLE INFO ABSTRACT Keywords:Cadmium coating replacement Aluminum slurry Steel Atmospheric corrosión Aeronautical applicationsCadmium has been widely used as a coating to provide protection against galvanic corrosión for steels and for its natural lubricity on threaded applications. However, it is a toxic metal and a known carcinogenic agent, which is plated from an aqueous bath containing cyanide salts. For these reasons, the use of cadmium has been banned in Europe for most industrial applications. However, the aerospace industry is still exempt due to the stringent technical and safety requirements associated with aeronautical applications, as an acceptable replacement is yet to be found. Al slurry coatings have been developed as an alternative to replace cadmium coatings. The coatings were deposited on AISI 4340 steel and have been characterized by optical and electrón microscopy. Testing included salt fog corrosión exposure, fluid corrosión exposure (immersion), humidity resistance, coating-substrate and paint-coating adhesión, electric conductivity, galvanic corrosión, embrittlement and fatigue. The results indicated that Al slurry coatings are an excellent alternative for Cd replacement.

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Active metal-based corrosion protective coating systems for aircraft requiring no-chromate pretreatment

Cited by 63 publications

References 30 publications

Lithium salts as leachable corrosion inhibitors and potential replacement for hexavalent chromium in organic coatings for the protection of aluminum alloys

Lithium salts as leachable corrosion inhibitors and potential replacement for hexavalent chromium in organic coatings for the protection of aluminum alloys

Protective Film Formation on AA2024-T3 Aluminum Alloy by Leaching of Lithium Carbonate from an Organic Coating

Aluminum slurry coatings to replace cadmium for aeronautic applications

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